Hepatitis A
The differential diagnosis of infectious hepatitis includes infection with
hepatitis A, B, D (delta)
non-A, non-B (C, E) viruses
Epstein-Barr virus
cytomegalovirus
toxoplasmosis
leptospirosis
secondary syphilis.
The differential diagnosis of noninfectious hepatitis
drug-induced
alcoholic hepatitis
cirrhosis
hepatic tumor
abscess
Etiology:
HAV is a single-stranded RNA virus belonging to the picornavirus group.
It can survive readily in a variety of environments, including seawater.
Life cycle of the virus
Clinical Manifestations:
The incubation period is 2-8 weeks
Hepatitis A characteristically is an acute selflimited illness associated with fever, malaise, jaundice, anorexia, and nausea.
Symptomatic hepatitis occurs in approximately 30% of infected children younger than 6 years of age; few of these children will have jaundice.
Among older children and adults, infection usually is symptomatic and typically lasts several weeks, with jaundice occurring in approximately 70%.
Prolonged or relapsing disease lasting as long as 6 months can occur.
Fulminant hepatitis is rare but is more frequent in persons with underlying liver disease.
Chronic infection does not occur unlike HBV
No increased risk for hepatic carcinoma unlike HBV
Recovery is generally complete with lasting immunity
Epidemiology:
Trasmission
The most common mode of transmission is person-to-person, resulting from fecal contamination and oral ingestion, ie, the fecal-oral route. Eating raw oysters harvested from fecally contaminated water. Filter-feeding shelfish, such as oysters, clams and mussels are believed to concentrate the virus.
In most infected persons, the highest titers of HAV in stool occur during the 1 to 2 weeks before the onset of illness, when patients are most likely to transmit HAV.
Common-source foodborne outbreaks occur
People at risk
A close personal contact with a person infected with hepatitis A
household or personal contact with a child care center
international travel
a recognized foodborne
waterborne outbreak
male homosexual activity
use of injection drugs
In developing countries, where infection is endemic, most persons are infected during the first decade of life; in developed countries, infection may occur at an older age.
Diagnostic Tests:
Serologic tests for HAV-specific total and immunoglobulin (Ig) M antibody are available.
Serum IgM is present at the onset of illness and usually disappears within 4 months but may persist for 6 months or longer.
Presence of serum IgM indicates current or recent infection
The presence of IgG antibodies to -HAV without IgM indicates past infection and immunity.
Virus is not cultivable. Direct detection by immunologic or EM not widely available
Treatment:
Supportive
Isolation of the Hospitalized Patient
In addition to standard precautions, contact precautions are recommended for diapered and incontinent patients
The major methods for prevention of HAV infections are improved sanitation and personal hygiene
Children and adults with acute HAV infection who work as food handlers or attend or work in child care settings should be excluded for 1 week after onset of the illness.
Prevention
Factors to consider in choosing active and/or passive prophylaxis include the interval before departure, the relative costs and availability of IG and hepatitis A vaccine, the duration of the stay, and the likelihood of repeated exposure during subsequent travel
Immune Globulin.
Immune Globulin (IG), when given within 2 weeks after exposure to HAV, is greater than 85% effective in preventing symptomatic infection.
To travellers to high endemic areas
Protection lasts for 6 months. To be repeated if staying longer.
Hepatitis A Vaccine
Two inactivated hepatitis A vaccines currently are available in the United States. Immune globulin is considered protective against hepatitis A immediately after administration, whereas the precise time required from receiving 1 dose of vaccine to onset of protection has not been established but likely requires 2 to 4 weeks.
Efficacy.
In double-blind, controlled, randomized trials, the protective efficacy in preventing clinical hepatitis A was 94% to 100%.
Duration of Protection.
The need for booster doses cannot be determined because hepatitis A vaccines have been under evaluation for only a short time.
Who to administer
International travellers to endemic areas
Children who live in endemic areas
Homosexual men
Food handlers
To a community to control an outbreak
General measures: Eat only adequately cooked seafood. The virus is inactivated by boiling for 1 munute.