Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures

Victorian statutory requirement

Hepatitis A infection (Group B disease) must be notified in writing within five days of diagnosis.

School and child care exclusion are outlined below (see Control measures).

Infectious agent

Hepatitis A virus (HAV) is the causative agent.

Identification

Clinical features
Illness due to hepatitis A typically causes acute fever, malaise, anorexia, nausea and abdominal discomfort. This is followed a few days later by dark urine and jaundice. Symptoms usually last several weeks although convalescence may sometimes be prolonged. Severe illness may rarely occur when hepatitis A infection complicates pre-existing liver disease. Infants and young children infected with HAV may have a mild illness with few or no symptoms, with jaundice often being absent.

Method of diagnosis
A blood test indicating IgM anti-HAV antibodies confirms recent infection. These antibodies are present for two to four months after infection. IgG antibodies alone are evidence of past infection.

In the acute stage of the illness, blood biochemistry shows elevated transaminase levels indicating hepatocellular damage. The pattern of liver function tests may be non-specific in later illness.

Incubation period

The incubation period is fifteen to fifty days, with an average of 28–30 days.

Public health significance & occurrence

Hepatitis A occurs worldwide. In developing countries most people are infected during childhood. With good sanitation and hygiene in the developed world, most people now reach adulthood without experiencing infection. There are about 70–200 cases per year in Victoria. Notifications have been declining nationally since the late 1990s. Infection is more common in travelers to endemic areas, injecting drug users, children in childcare and men who have sex with men.

Common source outbreaks due to contaminated food are rare.

Reservoir

Humans.

Mode of transmission

Infection is transmitted by the faecal-oral route from person to person or via fomites. Infectious food handlers may contaminate non-cooked foods such as salads.

Infection can also occur through ingestion of contaminated food or water. Filter-feeding shellfish such as oysters raised in contaminated waters may harbour the virus.

The precise timing and mode of transmission are often difficult to define.

Period of communicability

Cases are most infectious from the latter half of the incubation period until a few days after the onset of jaundice, corresponding to a peak in transaminase levels in cases without jaundice. Most cases are not infectious after the first week of jaundice. Long term carriage or excretion of the virus does not occur.

Susceptibility & resistance

All non immune people are susceptible to infection. Immunity after infection is probably lifelong.

Control measures

Preventive measures
Education about good hygiene is important, particularly hand washing before handling food and eating and after using the toilet. Inadequate sanitation and housing may contribute to endemic illness.

Inactivated hepatitis A vaccines are available for use in persons two years of age and over. Protection begins within 14–21 days after the first dose. A second dose is required for long term protection. The vaccine is recommended for travellers to high risk areas, persons in high risk occupations such as childcare workers and emergency services personnel, injecting drug users and men who have sex with men.

Control of case
Treatment is generally supportive.

Exclude from childcare, school or work for at least one week after the onset of illness or jaundice and until they are well.

Children must have a medical certificate of recovery before returning to school or child care.

Educate the patient and their family on the need for strict hygiene practices.

Infected persons should not prepare meals for others while infectious, nor share utensils, toothbrushes, towels and face washers.

Dispose of or thoroughly wash nappies of infants that have hepatitis A.

Control of contacts
Normal immunoglobulin (IG) 0.02 mL/kg body weight intramuscularly is recommended for:

• household and sexual contacts of the case
• staff and children in close contact with a case in a childcare centre.

IG is not recommended for usual office, school or factory contacts. IG must be given within seven to ten days of exposure to be effective. IG is rarely given to persons exposed to a potential common source of hepatitis A such as food or water because cases related to such a source are usually recognised too long after the exposure for IG to be effective. Timely administration of IG will prevent or modify clinical illness for approximately six weeks after the dose. However, people exposed and infected before the administration of IG may still experience a mild infection, and may have the potential to infect others if strict personal hygiene is not maintained.

Surveillance of contacts in a household or workplace should be maintained.

Live vaccines such as Measles Mumps Rubella (MMR) should not be administered for three months after a dose of IG, and may also be ineffective if given in the 14 days prior to IG. Reschedule such routine vaccinations.

When the case is a food handler:

• consider serological testing of co-workers to determine whether they have been infected or are susceptible
• place uninfected susceptible co-workers under surveillance and give them IG prophylaxis. These persons remain at a risk of developing mild illness modified by IG but can generally continue to work provided good personal hygiene and food handling practices are maintained
• undertake surveillance for hepatitis A in patrons by seeking a history of exposure to the food premises from cases notified over the next two to three months
• carefully consider the role of the infected food handler. If transmission to patrons appears likely, consider urgent follow-up of exposed patrons to offer them IG prophylaxis. Note that when the index case is a patron, it is usually too late to offer IG prophylaxis to other diners, although personal contacts of the patron case should be offered IG according to the usual protocol.

When the case is a health care worker, the role of the case should be assessed and consideration given to the provision of IG prophylaxis for co-workers and patients in their direct care whilst infectious. Surveillance of contacts in the health care facility should be maintained.

Control of environment
A source of infection should always be sought. For apparently sporadic cases, consider contact with another known case and recent travel to an area where the disease is endemic. Acquisition of infection from young children, particularly those in childcare should be considered.

Special attention should be given to toilet hygiene in schools and childcare centres. Ensure that soap and water are available and are used regularly to wash hands.

Food premises, health care facilities or child care centres where a case has worked whilst potentially infective should be requested to carry out a clean up in accordance with the Department’s Guidelines for the investigation of gastrointestinal illness.

Outbreak measures

Clusters of cases possibly related to a single source will require epidemiological and environmental investigation, including case finding and surveillance and public health measures to prevent further cases.

Use of the hepatitis A vaccine in an outbreak setting is dependent on rapid identification of the outbreak and persons at risk, and the ability to achieve high vaccine coverage levels.