HEPATITIS (INFLAMMATION OF THE LIVER) IS CAUSED BY VIRUSES BUT CAN ALSO BE CAUSED BY AMOEBA AND TOXIC CHEMICALS. HEPATITIS ‘A’ FORMERLY KNOWN AS INFECTIOUS HEPATITIS IS CAUSED BY ss RNA VIRUS OF THE Picornaviridae FAMILY. TRANSMITTED BYFAECAL/ORAL ROUTE WATER AND FOOD CONTAMINATION INCUBATION PERIOD OF 15 TO 40 DAYS AND BEGINS AS AN ACUTE FEBRILE ILLNESS, MALAISE, NAUSEA, DIARRHOEA, ABDOMINAL PAIN, LOSS OF APPETITE. THE VIRUSE REPLICATE IN THE GASTROINTESTINAL TRACT AND SPREAD TO THE LIVER , SPLEEN AND KIDNEYS. JAUNDICE IS CAUSED BY IMPAIRED LIVER FUNCTION AND BILIRUBIN ACCUMULATES IN TISSUES. CHRONIC INFECTIONS ARE RARE, RECOVERY IS USUALLY COMPLETE AND CONFERS A LIFE LONG IMMUNITY. A VACCINE FOR HEP ‘A’ HAS BEEN AVAILABLE SINCE 1995. SHOULD BE TAKEN BY: ALL CHILDREN 12 TO 23 MONTHS. PERSONS TRAVELLING TO CENTRAL /SOUTH AMERICA. MEN WHO HAVE SEX WITH MEN PERSONS WHO USE STREET DRUGS PERSONS WITH CHRONIC LIVER DISEASE PERSONS RECEIVING CLOTTING FACTOR CONCENTRATES

PERSONS WORKING IN HAV LABORATORIES. HEPATITIS B ALSO CALLED SERUM HEPATITIS IS CAUSED BY A ds DNA OF THE FAMILY Hepadnaviridae. THE ds circular DNA HAS A GAP IN ONE STRAND THAT HELPS IT INSERT INTO LEVER CELL DNA. THOUGHT TO BE A FACTOR IN DEVELOPING LIVER CANCER. IT CAN BE TRANSMITTED: INTRAVENOUSLY PERCUTANEOUSLY (INTO THE SKIN) ANAL/ORAL SEXUAL PRACTICES INGESTION OF BODY SECRETIONS (SEMEN, BREAST MILK). HEALTH CARE WORKERS ARE AT HIGH RISK OF INFECTION PROGRESS OF THE DISEASE: INCUBATION PERIOD IS 45 TO 180 DAYS VIRUS REPLICATES IN THE LIVER, LYPHOID TISSUE AND BLOOD FORMING TISSUE. PERSISTS IN THE BLOOD FOR YEARS AND CREATES A CARRIER STATE. ONSET OF SYMPTOMS IS INSIDIOUS AND FEVER IS UNCOMMON. OTHERWISE THE SYMPTOMS ARE SIMILAR TO HEP ‘A’.

CHRONIC ACTIVE HEP ‘B’ IS DANGEROUS BECAUSE IT DESTROYS LIVER CELLS. PREVENTION: VACCINE BECAME AVAILABLE IN 1986; IT IS MADE BY INSERTION OF THE VIRUS GENES INTO A PLASMID WHICH IS INSERTED IN A YEAST CELL THEREBY AVOIDING CONTACT WITH HUMAN CELLS. (TECHNIQUE IS CALLED: RECOMBINANT DNA). SHOULD BE TAKEN BY HEALTH CARE WORKERS, SEXUALLY ACTIVE. EVEN RECOMMENDED FOR PRETEENS AND IN USA GIVEN ROUTINELY TO BABIES TRAVELLERS TO THE TROPICS. MOST OF THE OLDER POPULATION REMAINS UNPROTECTED. WHEN GIVE TO HEP ‘B’-INFECTED PREGNANT WOMEN IT REDUCES FROM 90% TO 23% THE NUMBER OF INFANTS THAT WOULD BECOME CARRIERS. THIS NUMBER CAN BE REDUCED TO 5% IF GAMMA GLOBULIN IS GIVEN WITH THE VACCINE. IN SOME PARTS OF THE WORLD 90% OF MOTHERS ARE INFECTED. 40% OF CARRIERS DIE OF LIVER DISEASE. HEPATITIS C: CAUSED BY AT LEAST TWO UNCLASSIFIED RNA VIRUSES: ? FLAVIVIRUS ? TOGAVIRUS

THE LEADING REASON FOR LIVER TRANSPLANTS. SOURCE IS BLOOD AND BLOOD PRODUCTS, OCCASIONAL PLACENTAL TRANSMISSION. HAS TWO DIFFERENT INCUBATION PERIODS: EITHER 2 TO 4 WEEKS OR 8 TO 12 WEEKS. PROBABLY RELATED TO THE TWO DIFFERENT CAUSATIVE AGENTS. WHAT MAKES IT DIFFERENT TO OTHER HEPATITIS? LIVER DAMAGE IS MORE SEVERE WITH HIGH BLOOD CONCENTRATIONS OF: ALANINE TRANSFERASE THE DISEASE MAY APPEAR MILD BUT IT BECOMES SEVERE IN 80% OF THOSE INFECTED. 20% PROGRESS TO: CIRRHOSIS LIVER CANCER NO VACCINE IS AVAILABLE IMMUNITY DOES NOT FOLLOW INFECTION OF AN ESTIMATED 170 MILLION CARRIERS WORLDWIDE, OVER 4 MILLION LIVE IN THE USA. HEPATITIS D THIS IS CAUSED BY A ‘DEFECTIVE’ RNA VIRUS THAT HAS A HEPATITIS ‘B’ CAPSID.

IT IS CALLED DEFECTIVE BECAUSE ALONE IT CAN NOT CAUSE INFECTION. IT REQUIRES THE HBV AS A CO-INFECTING OR SUPER-INFECTING AGENT TO CAUSE DISEASE. HDV CAN CROSS THE PLACENTA. TOGETHER THEY CAN CAUSE DEATH. THE INCUBATION PERIOD IS 2 TO 12 WEEKS. VACCINATION AGAINST HBV WILL PROTECT AGAINST HDV. HEPATITIS ‘E’ CAUSED BY AN UNCLASSIFIED RNA VIRUS: CALCIVIRUS? ENTERICALLY TRANSMITTED/ FAECAL/ORAL. LARGEST OUTBREAKS OCCUR IN AFRICA/ASIA. MORE COMMON IN ADULTS. LOW MORTALITY (1%) BUT AS HIGH AS 20% IN PREGNANT WOMEN ALWAYS AN ACUTE CONDITION NEVER CHRONIC. ONE STRAIN OF HEV HAS BEEN FOUND IN PIGS AS WELL AS HUMANS. THE EPIDEMIOLOGICAL SIGNIFICANCE IS NOT KNOWN. RECENTLY 3 MORE HEPATITIS-LIKE VIRUSES DISCOVERED.