Chapter 2

Epidemics Fundamentals

Introduction Ancient people observed the incidental association of conspicuous natural events with outbreaks of epidemics and presumed that divine or supernatural forces were responsible for outbreaks. Smallpox (or “Mahamari”) epidemics in India were attributed to divine wrath. In Europe, increased incidence of rabies was observed at the time of rising of Sirius (“dog star”). In Egypt, outbreaks of gastrointestinal diseases that occurred as a result of flooding of the Nile were attributed to “fury of the Gods.” In 1717, Lancisi explained the origin of epidemics using the “miasma theory,” which was based on the assumption that when air was of “bad quality” (precisely undefined state), the persons breathing that air would become ill. In contagious diseases, the miasma was believed to pass on from affected individuals to susceptible individuals. Malaria (Latin Mal = bad) was attributed to miasma (Last, 1983). The predominance of cases of malarial fever in marshy areas led to the concept “bad air” causes malaria. Apart from these there are so many potential epidemics that impose a great threat to humanity. In response, the World Health Organization (WHO) ensures the international coordination of epidemic knowledge, particularly for diseases of international public health importance or when countries lack the capacity to respond to an epidemic themselves. These responses can vary from investigating the cause of an epidemic, to verifying and disseminating information, and to providing needed equipment and laboratory supplies.

Definitions ●

Epidemic: (Greek. Epi = upon; demos = people) is “an unusual or unexpected occurrence of a disease or a health-related condition in a region or a population, which is clearly in excess of the expected occurrence.” The expected (or usual) occurrence may vary from region to region (Bissell, et al., n.d.).

Emerging Epidemics: Management and Control, First Edition. Prakash S. Bisen and Ruchika Raghuvanshi. © 2013 John Wiley & Sons, Inc. Published 2013 by John Wiley & Sons, Inc.

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Endemic: (Greek. en = within; demos = people) is the constant presence of a disease or a health-related condition in a population in a particular geographical area, which is not imported from outside the area. Pandemic: (Greek. pan = all; demos = people) is an epidemic occurring over a wide area and usually affecting a large proportion of the world population. Elimination (of a disease): Elimination refers to the “termination of transmission of a disease from a large geographical region” (Dowdle, 1999). The term elimination is equivalent to “regional eradication.” Because diseases are not restricted to national boundaries, this definition is arbitrary. It can be thought of as a step ahead of control, progressing toward the eradication of a disease. The last reported case of guinea worm disease in India was in the year 1996. Measles has been eliminated from many developed countries. Andaman and Nicobar Islands (India), Australia, Britain, Cyprus, Finland, Gibraltar, Iceland, Ireland, Japan, New Zealand, Sweden, and Taiwan (China) are rabies free. Seas and oceans appear to form a natural barrier against the spread of rabies. Eradication (of a disease): This is the “termination of all transmission of a disease by the extermination of the infectious agent through surveillance and containment” (Dowdle, 1999). It denotes an irreversible, enduring, extermination of the infectious agent, without the possibility of its persistence in humans, animals, or the environment. Smallpox is the sole example of an eradicated disease. WHO declared global eradication of smallpox on May 8, 1980. Surveillance: refers to “continuous scrutiny (or vigil) over the factors in the agent, host and environment, and the occurrence, frequency and distribution of diseases and health-related events in the community” (Manitoba Health, n.d.) Reservoir of infection: is “any person, animal, arthropod, plant, soil, or a combination of these, in which an infectious agent normally lives and reproduces itself in such a manner that it can be transmitted to a susceptible host.” It has also been defined as “an ecological niche in which an infectious agent persists by a cycle of transmission or reproduction or both.” Thus, a reservoir is a “natural habitat (animate or inanimate), in which an infectious agent metabolizes and replicates” (Last, 1983). Agent: A physical, chemical or biological factor, whose presence (e.g., pathogen), excessive presence (e.g., hypervitaminosis), or relative absence (e.g., hypovitaminosis) is responsible for the occurrence of a disease. Clinical algorithm (synonym: clinical protocol): is an explicit description of steps to be taken in patient care in specified circumstances. The algorithmic approach uses branching logic and all pertinent data to arrive at decisions that yield maximum benefit and minimum risk. Natural history (of a disease): Many diseases have well-defined stages, such as stage of pathogenesis, presymptomatic stage, and symptomatic stage. Early detection and intervention may alter the natural disease process.

Declaring an Epidemic A disease can occur both as an epidemic or an endemic, depending on the relative number of cases. For example, consider a hypothetical locality with a population of 100,000 where the monthly incidence of gastrointestinal diseases in July and December is about 900 and 130, respectively. The occurrence of 1,400 cases of gastrointestinal diseases in July of a given year would be considered as an epidemic, whereas the occurrence of 150

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cases in December would constitute an endemic. On the other hand, the occurrence of a single case of a communicable disease, which is absent for a long period from the given area or population, may be labeled as an epidemic. For an example, smallpox is one of the two infectious diseases to have been globally eradicated; the other is rinderpest, which was declared eradicated in 2011 (Tognotti, 2010; The Mail and Guardian, 2011). The expected occurrence of any of these diseases is zero. Thus, the occurrence of even a single case of smallpox or rinderpest anywhere in the world will be clearly in excess of  expected occurrence and will be considered an epidemic. Likewise, the first case of a  disease, not previously known in that region, may be considered as an epidemic. The expected occurrence of yellow fever in India is zero. Hence, the occurrence of even a single case of yellow fever anywhere in India would be considered as an epidemic. It is difficult to label a disease as an epidemic in a region where it is normally endemic. If the number of cases were more than two standard deviations from the mean number of cases (mean endemic frequency), the disease would be labeled an “epidemic” (Last, 1983).

Control of a Disease According to Centers for Disease Control and Prevention (CDC; 1999), control refers to the “ongoing operations aimed at reducing the prevalence of a disease to a level where it is not a public health problem.” This definition implies that interventional measures are used to achieve the reduction in prevalence to a level at which the disease is not a public health problem, however, transmission of the disease may continue. The level of prevalence at which control is considered as achieved is fixed arbitrarily and varies for each disease. The parameters for control of a disease would depend on various factors such as availability of resources for control operations, level of knowledge and technology, and sociopolitical conditions. During an epidemic, the emphasis is on the control of the epidemic because many diseases cannot be eliminated because of the carrier state of the disease (a state in which individuals harbor the pathogen, without manifesting clinical symptoms), unknown modes of transmission, vector resistance, and resistance of the causative organism.

Types of Epidemics An epidemic outbreak usually follows a pattern based on environmental conditions and host factors (distribution, behavior, and sociodemographic characteristics). The epidemic tends to recur if these conditions remain persist. Hence for the prevention and control of epidemics, it is essential to know the types of epidemics and conditions that allow them to occur.

Point-Source Epidemics (Single-Exposure Epidemics) A point-source outbreak is a common source outbreak in which the exposure period is relatively brief, and all cases occur within one incubation period. In these epidemics, the affected population is exposed to the causative agent at only one point of time. When the exposure is brief and simultaneous, all the vulnerable persons are usually affected during the incubation period of the disease. The time after which half of the cases will occur is called the median incubation period. The epidemic curve shows only one spurt, which rises

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14 Number of cases

12 10 8 6 4 2 0 1

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11 13 15 17 19 21 23 25 27 29 Onset of days

Figure 2.1.

Point-source epidemic curve.

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Number of cases

12 10 8 6 4 2 0 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 Onset of days

Figure 2.2.

Propagated epidemic curve.

steeply and declines equally abruptly (Figure 2.1). In explosive epidemics, the epidemic curve shows “time-clustering” of cases during a narrow time interval. Examples include epidemics of food poisoning, accidents such as the Bhopal gas disaster in India and the Chernobyl nuclear accident in the former Soviet Union, which was the worst nuclear power plant accident in history (Last, 1983; Black, 2011).

Propagated Epidemics (Continuous- or Multiple-Exposure Epidemics) A propagated outbreak is one that is spread from person to person. Because of this, propagated epidemics may last longer than common-source epidemics and may lead to multiple waves of infection, if secondary and tertiary cases occur. In these outbreaks, the affected population is exposed to the causative agent continuously. Such an epidemic continues, with a radial spread, until the source of infection is removed or controlled. The epidemic curve shows multiple spurts, which rise and fall (Figure 2.2), depending on the number of persons affected (secondary cases). The fall of the curve is slow, and it ends when the vulnerable population is either depleted or protected by interventional measures. A propagated epidemic of a disease with a short incubation period and high secondary

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Table 2.1. Differences between point-source and propagated epidemics. Features

Point-Source Epidemics

Propagated Epidemics

Type of exposure

Exposure to causative agent is simultaneous and from a common source

Exposure to causative agent is not simultaneous, but through a chain of successive transmission

Clinical manifestations

Clinical manifestations occur in all affected persons within the range of a single incubation period

Clinical manifestations occur in affected persons within the range of a number of incubation periods

Control

Usually controlled by intervention at the source of epidemic

Usually controlled by interruption of chain of transmission

Epidemic curve

Epidemic curve exhibits single, rapid spurt; there are no secondary curves*

Epidemic curve exhibits gradual rise and multiple spurts†

Eradication

The epidemic ends with cessation of exposure to source or with initiation of control measures

The epidemic ends when the susceptible population is depleted or protected by control measures

*Epidemics of cholera may start as point-source epidemics and continue as propagated epidemics. † Epidemic curve of diseases with short incubation periods (such as cholera) may show a rapid rise and rapid fall.

attack rate (a highly infectious disease) will exhibit a rapidly rising and falling epidemic curve similar to that of a point-source epidemic. The speed of spread of the epidemic depends on host behavior, population density (which also determines the opportunity for contact), herd immunity, and secondary attack rate (Last, 1983). Propagated epidemics are infectious in origin; examples include epidemics resulting from contamination of food by food handlers (such as typhoid carriers), gastroenteritis or cholera resulting from contamination of food or drinking water, sexually transmitted diseases, conjunctivitis, air-borne diseases, and vector-transmitted diseases such as malaria. Table 2.1 shows the cardinal differences between point-source and propagated epidemics.

Seasonal Cyclicity of Epidemics Seasonal cyclicity refers to the annual cycling of incidence on a seasonal basis. Many infectious diseases exhibit increased incidence during certain seasons because environmental conditions favor transmission of the disease. A few health-related events also recur cyclically as a result of absurd human behavior; for example road accidents show an increased incidence during the New Year because of drunken driving. Demographic phenomena (marriages, births) also exhibit seasonal cyclicity (Last, 1983). Examples include: ●

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Monsoon: road accidents, water-borne and housefly-borne diseases (gastroenteritis, poliomyelitis), malaria, and snakebites Winter: air-borne diseases (upper respiratory tract infection, meningococcal meningitis) Early spring: measles and chickenpox Spring: asthma and hay fever Summer-Stroke and gastroenteritis.

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Secular Cyclicity of Epidemics Secular cyclicity refers to the long-term (more than 1 year) cycling of incidence of diseases. Epidemics of infectious diseases usually follow a pattern and repeat periodically when conditions are conducive for disease transmission, and there is an increase in the number of compromised patients (such as nonimmune children) in a relatively stable population. Epidemics of measles are known to occur in a cycle of 2 to 3 years, whereas hepatitis A has a higher incidence, every 7 years. Creation of herd immunity in the population (through natural infection or immunization) tends to break this cycle, preventing the disease from occurring as an epidemic (Last, 1983). Prior knowledge of cyclicity of epidemics can help in timely initiation of control measures.

Epidemics of Noncommunicable Diseases Because of altered human lifestyle, the incidence of health-related events, such as accidents, and that of noncommunicable diseases, such as cancer, coronary heart diseases, diabetes mellitus, and mental/psychosomatic diseases, have shown a progressively increasing trend. Timely interventions (mainly comprising risk assessment and behavior modification) can control this epidemic (Last, 1983).

Epidemiological Triad As described in the previous chapter, an epidemiological triad represents the interaction between an agent, host, and environment or place within a specific time dimension (Figure  2.3); these three epidemiological factors are responsible for determining the

Agent − Causative factors − Risk factors − Environmental exposures

Time − − − −

Host – Person characteristics − Group and population demographics

Time characteristics Incubation/latency Length of disease process Trends and cycles

Environment − Place characteristics − Biological, physical, and psychosocial environments

Figure 2.3. An epidemiological triad. Source: Miller RE. 2002. Epidemiology for Health Promotion and Disease Prevention Professionals. New York: The Haworth Press.

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occurrence, distribution, and frequency of a communicable or noncommunicable disease or a health-related condition such as accidents (Miller, 2002). The agent is a necessary factor, which has to be present for morbidity, although it may not inevitably lead to disease. To perpetuate a disease, it requires the combination of sufficient factors, which include a host that might be an individual or group of susceptible individuals and an environment.

Agent Factors ● ●

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Physical: heat, cold, light, noise, vibration, or radiation. Chemical: endogenous (uremia, ketone bodies, bilirubin) and exogenous (pollution, food additives, food adulterants, pesticide and fertilizer residues in foods, extrinsic toxins in foods). Biological: microorganisms (protozoa, bacteria, viruses), vectors, or rodents. Nutritional: excess or deficiency of nutrients, intrinsic toxins in foods. Social: poverty, lifestyle, or addictions.

For noncommunicable diseases, such as hypertension, diabetes mellitus, and obesity, the agent factor cannot be clearly identified, and the etiology is discussed in terms of risk factors. Multiple risk factors that may cause a disease have to be directly or indirectly related to this triad. These risk factors may be: ● ● ● ● ●

Causative: tobacco smoking, and lung cancer Contributory: lack of exercise and ischemic heart disease Predictive: maternal illiteracy and protein energy malnutrition in children Additive: tobacco smoking and occupational exposure to dust Synergistic: tobacco smoking and hypertension

Host Factors Host factors may be non-modifiable (not amenable to alteration) or modifiable (amenable to alteration by the action of the host). Nonmodifiable host factors may be demographic (age, sex, ethnic, racial) and biological (genetic, immunity). The modifiable host factors are socioeconomic, educational (poverty, illiteracy), and lifestyle (food habits, clothing, housing, recreation, occupation).

Environmental Factors ● ● ● ●

Physical: air, water, soil, terrain, lighting, ventilation, noise, or vibration Chemical: pollutants or pesticide contamination of the food chain Biological: microorganisms (protozoa, bacteria, viruses), vectors, or rodents Psychosocial and Cultural: fads, beliefs, peer pressure, traditions, or taboos. These are responsible for drug abuse, gender discrimination, promiscuity, and juvenile delinquency.

All the three factors (agent, host, and environment) of an epidemiological triad are not the watertight compartments. For example, food may be the agent factor for overnutrition,

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undernutrition, and specific deficiency diseases. It is the host factor when the nutritional status of the individual is considered. Food becomes an environmental factor when it is a vehicle for food poisoning or carcinogens. In combination, these three factors determine the onset and distribution of disease in individuals and groups. A disease will occur only if the situation is favorable in relation to these three factors. Reduction or elimination of any one factor leads to reduction or elimination of the other factors. Thus, the concept of an epidemiological triad provides multiple approaches for prevention and control of diseases.

Forecasting an Epidemic The manifestation of an epidemic in a given community depends on social and demographic characteristics of the host population, cultural behavior and lifestyle, environmental factors, and genetic changes in the causative agent; thus an epidemic may not always exhibit its distinguishing features and may present with unusual manifestations. Accurate data is essential for forecasting an epidemic. The data sources for forecasting epidemics are given in Figure 2.4. Along with the analysis of data, it is important to identify environmental conditions that are favorable for outbreaks. A hot summer may lead to shortage of drinking water, and thus, an epidemiologist can anticipate an epidemic of water-borne diseases resulting from consumption of contaminated water. Similarly, one can forecast the likelihood of  water-borne and mosquito-borne diseases in cases of heavy monsoons because of contamination of drinking water and water logging.

Surveillance Data Surveillance is the French word for “watching over.” It is the monitoring of the behavior, activities, or other changing information, usually of people for the purpose of influencing, managing, directing, or protecting (Lyon, 2007). Disease surveillance is monitoring the progress of a disease in a community. Surveillance data represents an important data source for forecasting an epidemic. Active Surveillance Active surveillance is an active search for detecting diseases that are not recorded under routine system of reporting (passive surveillance). This includes the sampling Data sources $ATAFROMHEALTHCARESYSTEM

Surveillance data s!CTIVESURVEILLANCE

s$ATAFROMPUBLICHEALTHSYSTEM

s0ASSIVESURVEILLANCE s3ENTINELCENTERS

s$ISEASENOTIFICATIONBYPRIVATE MEDICALPRACTITIONERS

s%PIDEMIOLOGICALINVESTIGATIONS

s,AYREPORTINGBYSPOTTERS

s3AMPLESURVEYS

Figure 2.4.

Data sources for forecasting epidemics.

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of clinically normal samples of the population, which are useful in the surveillance of diseases in which subclinical cases and carriers predominate. Recognition cards, showing the typical symptoms of a particular disease, have been used for active case  detection of guinea worm disease, poliomyelitis, and neonatal tetanus. Active surveillance is carried out for malaria, diarrheal diseases, acute respiratory infections, and diseases prevented by  vaccine. Health-care personnel, school teachers, and  community leaders report easily recognizable conditions such as acute flaccid paralysis and diseases such as malaria, measles, and tuberculosis. Although time consuming and costly, active surveillance remains one of the most effective techniques in forecasting an epidemic. Passive Surveillance Passive surveillance is the examination of only clinically affected cases of specified diseases in the population. Passive surveillance is a cost-effective and uncomplicated technique for surveillance of disease and early forecasting of epidemics. Routinely collected data from various levels of the public health care system are reported in a standard format to the health authorities. Examples of diseases monitored nationwide are tuberculosis, poliomyelitis, diphtheria, pertussis, tetanus, measles, diarrheal diseases, cholera, malaria, dengue fever, hemorrhagic fevers, viral encephalitis, syphilis, gonococcal infections, meningococcal infection, influenza, enteric fever, chicken pox, and viral hepatitis. Data from Sentinel Centers Sentinel centers provide reliable information on selected diseases so that immediate action can be initiated. Criteria for selecting a sentinel center include high patient load in the institution, availability of accurate diagnostic facilities, and a reliable recording and reporting system. Immediate intervention is required if any abnormal increase in number of cases is reported as compared to the corresponding period in the previous years. Seasonal pattern of diseases can also be clearly established from data provided by sentinel centers. A disadvantage of sentinel surveillance is that sentinel centers provide selective data on patients attending these centers. This data cannot be extrapolated to indicate a trend of a disease in a locality. Data from Epidemiological Investigations Epidemiological investigations are useful in identifying cases, their age and sexdistribution; determining the geographical distribution of cases (using spot maps); incubation period and duration of an epidemic (from epidemic curve); determining the mode of  transmission; and deciding the mode of intervention to contain the spread of an epidemic. Sample Surveys A sample survey is an active method of surveillance that is also used to assess outcome of interventional measures. Its disadvantages include its high cost, need for trained highly skilled personnel, and difficulty in conducting the survey.

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Data from Health-Care System Data from Public Health-Care System Routine reports are collected on a monthly basis from all levels of the health-care system in the public sector and are compiled at district and state levels. Notification Notification of diseases by private medical practitioners also helps in early detection of outbreaks. Unfortunately, this system is still inadequate in many countries of the world, including India. Moreover, the list of diseases that need to be reported has interstate variations. Lay Reporting by Spotters Spotters are laypersons from the local community (school teachers and community leaders), who help in early detection of outbreaks. These spotters can report easily recognizable diseases such as diarrhea, malaria, measles, and chicken pox with reasonable accuracy.

Forecasting Techniques Trends are analyzed by tabulating data on incidence and prevalence of morbidity and mortality and age and sex distribution on a monthly basis (for the corresponding months of the previous 3 years) and on an annual basis (for at least 3 years). The data should be depicted graphically and examined for seasonal and cyclic variation. Spot maps should also be used to detect geographical clustering of cases.

Contingency Plan Ideally, the contingency plan should fit into the administrative structure of the state and should also be integrated into the existing plan for disaster preparedness. This involves preparation of inventory of the existing and required resources and a plan for mobilization of these resources.

Manpower Various categories of manpower, from all possible sources, are to be listed and later trained. They should be available for mobilization at short notice. It is essential to prepare a list (containing names, addresses, contact numbers) of medical specialists, medical practitioners, laboratory technicians, and paramedical workers working in the governmental, nongovernmental and voluntary, and private sectors. For epidemics of zoonotic diseases, the services of veterinary doctors may be required. These trained personnel should be oriented about their role in the event of an epidemic. Volunteers are indispensable during emergencies. A list (containing names, addresses, and contact numbers) of all possible local volunteers, socially active individuals, and community leaders should be prepared with the help of voluntary and philanthropic organizations, and these persons should also be trained about their role in the event of an epidemic.

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Money A list of all the sources from where funds may be available in the event of an epidemic should be prepared so that the persons in charge of managing the epidemic know the exact amount of available money. Heads of expenditure are to be listed. Voluntary and philanthropic organizations can donate money, and socially active individuals can  help in getting donations. Their names, addresses, and contact numbers should also be listed.

Materials A list of all equipment (for laboratory investigations, resuscitation, clinical management, and vaccination) and drugs (including vaccines) that would be necessary for managing common epidemics should be prepared. Organizations (pharmaceutical manufacturers and suppliers; voluntary and philanthropic institutions) that may be willing to supply or assist in procuring vaccines, medicines, and equipment during an emergency should be identified. All the voluntary agencies, schools, community centers, and recreation facilities that are willing to provide accommodation and food for volunteers and other personnel during an emergency should also be listed.

Transport Transport is required for movement of health-care personnel, volunteers, and for sending patients to referral hospitals. A list of all the available ambulances and vehicles such as buses, trucks, and pick-up vans that can be used as ambulances during an emergency should be compiled. All the organizations and individuals, who would be willing to provide vehicles (by type of vehicle) for transporting volunteers and other personnel during an emergency, should be enlisted.

Hospitals and Health Facilities Locations of all existing hospitals and health facilities (government, municipal, private) are to be listed with the available number of beds and facilities, such as isolation ward, intensive care unit, and ambulance. The names, addresses, and contact numbers of managerial and specialist staff is also to be recorded. Schools, community centers, and recreation facilities can also be converted into temporary hospitals and outpatient facilities.

Media During an outbreak, it is necessary to disseminate correct information quickly and efficiently, using all available media. Along with health messages on prevention and control measures, it is essential to give a correct daily update on the epidemic situation. For this purpose, arrangements are required with local radio stations, cable television operators, and local newspapers for delivering health messages. As a result of current technological advances, it is also possible to send text messages to a large number of people through cell phones.

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Laboratory Support A list of the essential routine and special laboratory investigations that are required to be carried out for various infectious diseases and the laboratories (at local, regional, and national levels) that carry out these tests should be prepared. For carrying out special investigations, a referral system should be developed and should also mention the method of transporting samples to the laboratory.

Investigation of Epidemics Verification of Initial Reports The initial report of an outbreak may be obtained from active, passive, and sentinel surveillance reports; reports from health facilities; reports in the media; and reports from the community itself. All initial reports, including rumors, must be investigated thoroughly. Information should be collected from all possible sources and verified. A  retrospective study should be carried out in all health facilities, using records of patients for the past few months. Emphasis should be given to old cases in which the clinical manifestations were similar to that in the present outbreak and cases with unconfirmed diagnosis. An investigating team should visit the area from where the cases have been reported. On confirming the outbreak, steps should be initiated immediately for investigation and management. Investigation of an epidemic should go  on simultaneously with control operations. Investigation into the etiology of the epidemic will help in preventing its recurrence. Various aspects to be probed include person distribution (age, sex, occupation, and other host factors); place distribution (geographical areas affected); possible etiology for the outbreak; and measures for containing the epidemic.

Steps for Case Definition In the absence of standard case definitions, a provisional case definition should be prepared before an attempt to investigate an epidemic. The case definition includes usual and rare manifestations of the disease and criteria for deciding a “suspect,” “probable,” and “confirmed” case. ●

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Suspect case: The clinical manifestations are similar to that of the disease under investigation, but laboratory evidence of infection is lacking. Probable case: The clinical manifestations are similar to that of the disease under investigation, and the laboratory reports are suggestive of recent infection, but the reports do not provide conclusive evidence of infection. Confirmed case: The laboratory reports establish recent infection.

Formulating a Working Hypothesis The working hypothesis should be based on the manifestations of the disease and its mode of transmission. This working hypothesis is subject to further modification or alteration based on the details ascertained during the investigation.

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Field Investigation and Case Finding Investigating teams should be sent at the earliest available time to the area where the outbreak is reported. The size of the investigating teams will depend on the extent of the affected area, geographical factors such as terrain and accessibility, and density of population in the affected area.

Laboratory Investigations Laboratory examinations are essential for the diagnosis of a confirmed case. If laboratory facilities are lacking in a particular area, the specimens should be sent to other regional or national-level laboratories for the confirmation of diagnosis. Once the diagnosis is confirmed by laboratory reports in a few cases, it is not necessary to wait for laboratory confirmation for other cases. For containing the spread of the epidemic, suspect and probable cases should also be treated as confirmed cases. A case investigation form is to be prepared for the investigation, and all investigators in the field should use this form. If it is not feasible to devise a common case investigation form that can be used for all types of epidemics, the reporting form should include: 1. 2. 3.

4.

5. 6.

7.

Serial number, name of the investigator, and the date of investigation. Personal particulars of the patient: full name, complete address with local landmarks, age, sex, occupation, and place of work. Current history: Source of drinking water at home and place of work (piped water supply, public well (bore or dug), private well (bore or dug), river or lake/pond.). History of disinfection of drinking water and details of meals or snacks consumed at home and place of work is also recorded. History of the past 6 months: places visited; history of food and water consumption (type of food, source of drinking water and place of consumption), vaccination or injections taken, history of contact with similar cases, and history of similar illness in the family. Clinical history and examination: date of onset of symptoms, symptoms (anorexia, diarrhea, vomiting, aversion to tobacco/alcohol, high-colored urine, jaundice), signs (hepatomegaly, icterus), and details of the treatment given. Laboratory investigations: This includes: (a) Clinical investigations: bile salts and pigments in urine, liver function tests, serum electrolytes, Australia antigen (b) Epidemiological investigations: chemical and bacteriological tests for drinking water and sewage Field investigations: (a) Community profile: geographical location, terrain, social classes, endemic diseases in the area, and history of outbreaks with dates (b) Sources of water supply: sources that were actually visited and verified (c) Disinfection of water: person responsible for disinfection; date of disinfection; disease vectors in the area such as houseflies, rodents, and cockroaches; hygiene in eating houses; storm water drains: underground or surface and fecal contamination of surface drains; human excreta disposal: sewerage system, septic tank, service-type, open-air defecation; irrigation: type of irrigation or sewage farming in the area.

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Detecting Source or Reservoir of Infection Sources of infection may be cases or carriers. The reservoir of infection may be animate or inanimate. After finding out the range of incubation periods (from the dates of onset of the disease in identified cases), the source of infection should be sought in the time span between the minimum and maximum incubation periods.

Contact Tracing Contact tracing refers to detection of cases or carriers among persons who come in any type of contact with the patient (members of the patient’s household, health-care personnel, sexual partners of the patient, etc.). Contact tracing yields information on the mode of transmission of the disease. Health-care personnel may be affected if the disease is transmitted by aerosols (air-borne droplets) or by contact with the patient’s body fluids. All contacts should be clinically monitored and given chemoprophylaxis or immunoprophylaxis, where available. In highly infective diseases, contacts can be classified, based on the risk of getting infected: ●

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Close contact: A person who has had occasional face-to-face contact with the patient, has shared the same meal or the same room, has handled the patient’s belongings, or has given personal care without personal protective equipment (masks, gloves) during the period of communicability of the disease. Possible or Casual contact: A person who does not fulfill the preceding criteria but may have been exposed in identical circumstances in the next bed, in the same hospital ward, or at the workplace, or in public transport.

Labeling and Information Specimens are to be clearly labeled with the following information: ● ● ● ● ● ● ● ● ●

Name of the patient and his or her registration number Name of the patient’s mother and father (for identification) Age, sex, and complete residential address of the patient Name and address of the institution sending the sample Date of onset of illness Date of hospitalization Date of collection of sample Brief clinical history, examination findings, and provisional diagnosis Results of clinical laboratory investigations.

Storage and Transportation of Specimens All samples and tissues should be stored and transported in appropriate media at the recommended temperatures. The laboratory that handles highly infectious pathogens must have high levels of biosafety. All the samples should be properly transported to the regional and public health laboratories.

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Data Analysis The disease causing the epidemic can be provisionally ascertained by recording the signs and symptoms up to the period of convalescence. It is possible to determine the incidence rate (the number of new cases per thousand population), the case fatality rate (the number of deaths among the cases divided by the total number of cases), and the probability of  continued spread of the epidemic by analyzing the epidemiological data. The data are  subjected to statistical analysis to confirm the observed mode of transmission. Data analysis helps in testing the working hypothesis. This can be further followed by preparation of spot maps and epidemic curve. Spot Map A spot map shows the geographic location of people with a specific attribute (Last, 1983). In epidemiology, spot maps are used to depict the geographical distribution of a disease or health condition. Spot maps are needed because geographical clustering of cases may not be reflected in morbidity and mortality statistics. The location of health-related events, such as cases and deaths, is depicted on a map. The map may be local, regional, national, or global, depending on the health-related event being studied. Spot maps provide information that is easy to grasp and available at a glance. The spot map depicts the progress of an epidemic: places affected at a given time, linear or centrifugal spread, and spread along water bodies. Clustering of cases gives clue about shared risk factor or common source of infection. Epidemic Curve An epidemic curve is a graph showing the distribution of cases by the time of onset (Last, 1983). The shape of the curve (rapid rise and fall; slow rise and gradual decline), number of spurts (single or multiple), and pattern of time-clustering reveal the type of the epidemic. It may reveal a relationship between incidence and various parameters (related to the host and outcome of interventional measures).

Management of Epidemics All categories of personnel working in the public health sector and private medical practitioners should immediately notify any occurrence of diseases to local government or municipal health authorities. While notifying, the following information, should be provided: ● ● ● ● ● ●

Name and address of the notifying health-care provider Name, age, sex, and address of the suspected case Date of onset of symptoms Dates and types of exposure to other affected persons Types of specimens collected for laboratory diagnosis Current status of the patient(s): whether cured, improving, worsened, or dead at the time of notification.

The number of new cases (incidence rate) is high for water-borne and air-borne diseases, and this may overburden the health care system. The response to such

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outbreaks would need the mobilization of personnel, materials, and temporary healthcare facilities (that should be identified in the contingency plan). If necessary, patients are to be hospitalized in an isolation ward, and procedures for concurrent disinfection carried out depending on the infectivity of disease. Routine health programs such as immunization should be continued in the event of an epidemic (Pan American Health Organization, 1985).

Control of Epidemics The chain of disease transmission may be broken by interventions at the level of reservoir or source of infection, route of transmission, and susceptible population.

Control of Reservoir or Source of Infection Control of Animal Reservoir or Source Zoonotic diseases, such as brucellosis, rabies, and anthrax, can be controlled by screening animals and animal handlers for infection; treating infected animals and humans; destroying infected animals; avoiding close contact with animals; licensing, restraint, and vaccination of pets; and meat inspection and meat hygiene at slaughter houses. Control of Human Reservoir or Source To control human reservoir, case detection should be performed. Active case detection is undertaken for the early detection of infectious diseases to curb their spread to susceptible, whereas passive case detection is done at health-care facilities. ISOLATION Infected persons or domestic animals should be separated from others, for the period of  communicability of the disease, to prevent direct or indirect transmission of the infectious agent. A patient may be isolated in the isolation ward of a general hospital or in a specialized isolation hospital. Home isolation may also be considered, provided preventive measures are undertaken. Home isolation is acceptable because it does not involve additional costs for the patient and also prevents nosocomial infections. The duration of isolation is disease specific because it should cover the entire period of communicability of the disease. QUARANTINE Quarantine is the limitation of freedom of movement of asymptomatic individuals or domestic animals suspected to have been exposed to a particular disease for the longest known incubation period of the disease to prevent contact with those not similarly exposed. Modified quarantine is a selective partial limitation of freedom of movement designed to meet particular situations. Exclusion of children from school is an example. International travelers (coming from an area, which is endemic for an internationally quarantinable disease) are compulsorily quarantined near international airports for a specified period if they do not have a valid vaccination certificates under the International Health Regulations formulated by WHO.

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HEALTH EDUCATION In the event of an epidemic, the entire community should be educated to modify behavior so that the health of the susceptible in the population is safeguarded. In the event of an epidemic, all diagnosed patients should also be advised about protective measures to prevent the spread of the disease. For example, in diseases such as enteric fever, patients continue to excrete pathogens during convalescence. Because it is not feasible to detect all such carriers in a locality by laboratory tests, all convalescing patients should be advised to take simple precautions and maintain good personal hygiene. CHEMOTHERAPY AND CHEMOPROPHYLAXIS Effective chemotherapy for the recommended duration will render the patient non-infectious. Chemoprophylaxis may be recommended for carriers and patients contacts to reduce the environmental load of pathogens. These contacts should also be observed for early symptoms and signs of the disease. LEGAL ASPECTS Many governments have enacted laws that enumerate a list of diseases that should be compulsorily notified to the local health authority.

Interrupting Transmission The transmission of endemic diseases can be interrupted by employing following measures: ●

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Safe and healthy housing: Poor housing and overcrowding are associated with increased risk of developing infestations such as skin diseases (resulting from increased physical contact), respiratory diseases (as a result of droplet infection), and diseases transmitted by vectors. Ventilation helps in diluting and removing the air-borne pathogens. Good housekeeping: Poor domestic and peri-domestic hygiene is responsible for providing hiding places for disease vectors such as arthropods and rodents. Dust suppression (by wet mopping of floors) can help in preventing transmission of air-borne infections. Disinfection and sterilization: Drinking water should be disinfected during epidemics of water-borne diseases. Disinfestation is the “destruction of ectoparasites and their ova by physical or chemical methods” (Montreal Protocol on substances that deplete the ozone layer, 1994). The method of disinfection will vary according to the mode of transmission of the disease. Disinfestation and vector control: This also includes the destruction of rodents, bedbugs, and fleas. Nursing techniques: Barrier nursing is also useful to interrupt the transmission. It  refers to the use of physical or chemical barriers by all categories of hospital personnel and is not restricted to nursing staff. Physical barriers include gowns, gloves, and other personal protective equipment (PPE), whereas washing hands with disinfectant constitutes a chemical barrier. The objective of barrier nursing is to prevent the spread of pathogens through the intermediary of hospital staff. Health-care providers with cuts, injuries, or infectious diseases should not be involved in patient care.

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While imparting mouth-to-mouth resuscitation, the risk of transmission of HIV is low. However, it is safe to use a barrier; placing a gauze piece on the patient’s mouth is advocated (Gangakhedkar, 1999). The  procedures for effective barrier nursing include: 1. Repeated hand washing after attending to each patient 2. Concurrent and terminal disinfection 3. Using PPE 4. Establishing multidisciplinary hospital infection control committee 5. Periodic supervision of disinfection 6. Microbiological surveillance Barrier nursing is indicated in high-risk areas such as infectious disease wards and hospitals, neonatal wards, premature baby units, intensive care units, postoperative wards, and burn wards. Avoiding physical contact: An individual should avoid physical contact with the source of infection. For example, in areas that are endemic for hookworm infestation, using footwear would help in avoiding physical contact with the source of infection (i.e., the soil). Likewise, using insect repellents, mosquito nets, and screening of houses will prevent mosquito bites. Food and milk hygiene: Taking precautionary measures during food handling, storage, cooking, and serving of food can prevent the transmission of many food- and milk-borne diseases. Care should be taken to prevent contamination of milk after it is pasteurized or boiled.

Protecting Susceptible Population The susceptible population should be protected by the socioeconomic development of a community, which leads to improved nutritional status. Nosocomial infections should be prevented by disinfection and sterilization of the hospital compound, isolating patients, and minimizing the number of visitors. Further immunoprophylaxis (prevention using active and passive immunizing agents as vaccines and antibody preparations) and chemoprophylaxis (use of chemotherapeutic agents in preinfection stage or in the incubation period to prevent the establishment of the pathogens) should be recommended depending on the type of infectious agent, severity of infection, and the immune state of the host. Chemoprophylaxis will be an effective measure only if the susceptible groups for the disease are easily identifiable, satisfactory compliance can be ensured, the risk of adverse effects and drug resistance is low, and the intervention is cost effective. It is difficult to distinguish between mass drug administration (also called “blanket chemotherapy”) and chemoprophylaxis in public health practice. This method is useful for covering short-term risk in an easily identifiable small group of persons with a high risk of developing a disease.

Principles of Planning Emergency Services Policies and Protocols The objectives of emergency care are to render effective emergency medical and surgical care, to act as a receiving area for immediate clinical care and evaluation of casualties

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during man-made or natural disasters, medico-legal conditions, psychiatric emergencies, etc., and to disseminate information about the emergency situation and casualties to the relatives, community members and the mass media. ●

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Policy decisions: While taking policy decisions on emergency care, guidelines for handling medico-legal and contagious patients; the financial policy such as hospital charges, if any; the scope of services to be provided; and the procedure for transfer/ referral to other hospitals are to be pre-decided. Procedural delays are to be minimized. Patients are usually kept in an observation room for a maximum of 8 to 12 hours. Acute conditions requiring observation include renal colic, chest pain/discomfort, bronchial asthma, and hypersensitivity reactions. Protocol for treatment: Written protocols should be prepared for clinical decision making and treatment. Its objective is to ensure maximum efficiency and uniformity with minimum wastage of time. Algorithms (step-by-step procedures) may be prepared for specific conditions, such as injuries, fractures, burns, and infectious diseases. These protocols and algorithms are to be prepared by a committee of experts in related faculties. Copies of these protocols must be displayed in emergency or casualty department. Policy on record keeping: Records (clinical notes, treatment given, referrals, copy of written instructions given to patients before discharge from hospital) should be kept because the emergency or casualty department is prone to legal liabilities. It is necessary to develop norms for storage, retrieval, and transfer of records. Staffing: Policy for securing services of all categories of staff is to be pre-decided. Written job description for each category of staff; round the clock duty roster for each category of staff (including telephone numbers of doctors and consultants); and alternative arrangement in case of absenteeism of staff is to be displayed. Chain of command: The chain of command is to be decided beforehand and is to be conveyed to all categories of personnel. Usually, hospital services are controlled by  three chains of command (administrative, medical, and nursing), but during emergencies, personnel from multiple organizations and multiple disciplines (medical and nursing personnel, home guards, fire brigade) may be deployed.

Classification of Emergency Facilities The US National Academy of Sciences has classified emergency facilities into four types (Table 2.2). Scope of services to be provided at each type of facility is to be pre-decided while planning emergency services. Types of Basic Infrastructure The types of infrastructure for an emergency facility include: ●

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Core type: Beds are located around a central nursing station. The patients will enter and exit cubicles through a peripheral corridor. Arena type: Basically a core type but without the peripheral corridor. The patients will enter and exit cubicles through the central arena. Corridor type: Many variations of this type are possible.

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Table 2.2. Types of emergency facilities. Feature

Type I

Type II

Type III

Type IV

Type of facility

Major

Basic

Stand-by

Referral

Staff

Specialists on round-the-clock duty, medical officers, and trained nurses

Medical officers on round-the-clock duty, specialists on call, and trained nurses

Emergency nurse and medical officer on call

Only emergency nurse OR auxiliary nurse on duty for first-aid purposes only

Example

Teaching hospital

Sub-district or district hospital

Primary health center

Sub-center

National Institute of Health and Family Welfare (NIHFW). 1993. Facilitator’s guide: Immunization handbook for medical officers. Accessed March 25, 2013, at http://nihfw.org/pdf/NCHRC-Publications/ ImmuniFacGui.pdf.

Basic Physical Infrastructure This should have a provision of a wide doorway with ramp for entry of stretchers, trolleys, and wheelchairs; provision for a parking space for vehicles such as ambulances and police vans; space to be provided for police checkpoint adjacent to emergency or casualty department; waiting area for visitors or relatives to be provided with public address system, public phones, drinking water, toilets, and seating facilities; isolation room for patients with contagious diseases; and sound-proof security room for noisy and disturbed or mentally ill patients.

Coordination ●

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Intra-institutional: coordination between pathology, microbiology, and biochemistry laboratories, radiography, electrocardiography, central sterile supplies department, maintenance and engineering, operation theater, labor room, pharmacy, stores, mortuary, super-specialty departments, and hospital administration. Only minimum and urgent investigations are to be ordered by the emergency or casualty department. Interinstitutional: coordination with related services in the locality and facilitates sharing facilities and help in immediate supplies during emergencies. These include other hospitals involved in health-care delivery including private medical practitioners, ambulance, hearse, blood banks, laboratories, and chemists. Intersectorial: coordination with the police department, home guards, press, and the electronic media. Written guidelines for reporting to mass media are to be specified. Only one responsible senior official is to be assigned to inform the mass media and community members. This arrangement should be known to all categories of staff.

Mobilization of Resources Resources (manpower, materials, and money) are best mobilized by establishing an emergency committee comprising the emergency medical officer, specialists, nursing staff, and hospital administration. Steps in resource mobilization include assessing existing procedures for emergencies; preparing a list of existing manpower and inventory of

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existing materials and equipment in the institution and other institutions in the locality; assessing additional resources required; and identifying resource persons in the locality and networking with them.

Quality of Emergency Services In most of the developing countries with a shortage of skilled health-care personnel and a large population, emergency departments may also provide basic health care to patients in need. This fact should be kept in mind while evaluating the quality of care. The parameters for evaluating quality include: ● ● ● ● ● ● ●

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mobilization of resources use of manpower team work maintenance of equipment availability of supplies quality of supervision Concurrent review: This includes assessment of patient care at the time of service delivery by observation and appraisal of client satisfaction by interviewing patients (feedback). Retrospective review: This is also called a medical audit and involves a systematic retrospective analysis of medical records. Retrospective review reveals conformity with pre-existing norms for emergency patient care and whether patient care was of acceptable quality and timely. It also helps in continuing improvement of quality of care, provides comparative assessment of patient care at present and in the past, and enables interventions for improving patient care strategies in future.

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National Institute of Health and Family Welfare (NIHFW). 1993. Facilitator’s guide: Immunization handbook for medical officers. Accessed March 25, 2013, at http://nihfw.org/pdf/NCHRCPublications/ImmuniFacGui.pdf. Pan American Health Organization (PAHO). 1985. The Earthquake in Mexico. Emergency Preparedness and Disaster Relief Coordination Program. Disaster Reports Series No. 3.Washington, DC: PAHO. The Mail and Guardian. 2011. The world is free of rinderpest. Accessed February 12, 2013, at http://mg.co.za/article/2011-05-25-the-world-is-free-of-rinderpest/. Tognotti E. 2010. The eradication of smallpox, a success story for modern medicine and public health: What lessons for the future? J Infect Dev Ctries 4:264–266.