Hepatitis A
*Onset of illness in adults is usually abrupt with fever, malaise, anorexia, nausea & abdominal discomfort followed within a few days by jaundice.
*in childhood the infection is asymptomatic or with a mild illness.
*the disease varies in clinical severity from a mild illness lasting 1-2 weeks to a severely disabling disease lasting several months.
* prolonged, relapsing hepatitis for up to one year occur in 15% of cases, no chronic infection is known to occur.
severity of illness increases with age. Reported mortality ranges from 0.1-0.3%, mortality is elevated to 1.8% for adults over 50 years, persons with chronic liver disease, HAV is considered a disease with a relatively low case fatality rate .
*diagnosis: demonstration of IgM Ab against HAV (IgM anti-HAV) which is detected 5-10 days after exposure. If lab test are not available, epidemiologic evidence may provide support for the diagnosis.
Infectious agent
HAV, a picornavirus (RNA virus)
Occurrence
world wide, sporadic & epidemic.
*Risk groups
-household &sexual contact of acute cases.
-day care centers.
-military personals.
-travelers to countries where the disease is endemic.
-injecting drug users.
-homosexual.
-poor sanitation & overcrowded.
Reservoir: humans.
Mode of transmission
1- Person to person contact by feco-oral route (the infectious agent is found in feces reaches peak levels 1-2 week before onset of symptoms & diminish rapidly after liver dysfunction or symptoms appear).
2- Contact with contaminated food or water by infected food handlers, including
Foods that are not cooked or are handled after cooking.
3- Injecting drug use (rare) .
4- Transfusion of blood & clotting factor (rare).
Incubation period: 15 – 50 days, average 28 – 30 days.
period of communicability: maximum infectivity occurs during the latter half of the incubation period & continues for a few days after the onset of jaundice. Most cases are probably noninfectious after the first week of jaundice, although prolonged viral excretion (up to 6 months) occurs in infant & children. Chronic shedding of HAV does not occur. *
Methods of controls:
A. preventive measures:
1- Educate the public about good sanitation & personal hygiene, hand washing &
Disposal of feces.
2- Proper water treatment & distribution systems & sewage disposal.
3- post-exposure prophylaxis : Studies of post exposure prophylaxis have involved strategies using passive immunoprophylaxis with immunoglobulin (IG) & HA vaccine .