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

School exclusion is not applicable.

Infectious agent

Hepatitis B virus (HBV) is the causative agent.

Identification

Clinical features
Less than 10% of children and only 30–50% of adults with acute HBV infections will have icteric disease. The onset is usually insidious with anorexia, abdominal discomfort, nausea, vomiting, lethargy and occasional rash and arthralgia. It often progresses to dark urine and jaundice. The severity of infection ranges from asymptomatic cases detected only after further investigation of abnormal liver function tests, to fulminating and often fatal case with extensive acute hepatic necrosis.

Method of diagnosis
HBV infection is confirmed by the detection of hepatitis B surface antigen (HBsAg) or of HBV DNA in serum. Serology determines whether infections are newly acquired or reflect chronic carriage.

Serology for newly acquired infections requires one of the following:

• detection of HBsAg in a patient shown to be negative within the last 24 months
• detection of HBsAg and high levels of specific IgM to hepatitis B core antigen (IgM HBcAg) in the absence of prior evidence of HBV infection
• detection of HBV DNA and high levels of specific IgM to hepatitis B core antigen (IgM HBcAg) in the absence of prior evidence of HBV infection.

Serology for chronic carriers requires:

• detection of HBsAg or HBV DNA in the serum of a patient on two occasions at least six months apart.

The following table summarises the interpretation of hepatitis B virus serology.

Source: Centers for Disease Control and Prevention (CDC).

Incubation period

The incubation period is 45–180 days with an average of 60–90 days.

Public health significance & occurrence

Hepatitis B virus is a major cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma.

An estimated two billion people have been infected with HBV worldwide, 350 million of whom are chronic carriers. Each year an estimated one million people die as a result of HBV infections and over four million new acute clinical cases occur.

In countries with low endemicity (HBsAg prevalence less than 2%) most infections occur in young adults and especially among persons who belong to known high risk groups. Risk of HBV infection increases with:

• unprotected sexual contact
• injecting drug use
• household and sexual contact with known HBV infected persons
• incarceration
• workplace exposure to blood.

In higher endemicity areas (HBsAg prevalence ? 2%) most infections occur as a result of perinatal transmission from HBsAg-positive mothers or early horizontal transmission via close contact in the household family setting.

Reservoir

Humans.

Mode of transmission

Although hepatitis B surface antigen (HBsAg) has been found in virtually all body secretions and excretions, only blood (serum or plasma), semen and vaginal fluids have been shown to be infectious.

Transmission occurs via percutaneous and permucosal exposure to contaminated blood and body fluids. This may occur during:

• sexual contact
• birth
• injecting drug use
• some household activities such as sharing razors or toothbrushes
• invasive procedures in the community such as tattooing or body-piercing, if there has been inadequate infection control
• invasive medical or dental procedures if there has been inadequate infection control.

All blood and blood products produced for medical purposes in Australia are carefully screened for HBV and other blood-borne viruses using nucleic acid testing.

Period of communicability

The blood of infected persons is infective many weeks before the onset of symptoms and remains infective through the acute clinical course of the disease and during the chronic carrier state, which may persist for life. The proportion of infected individuals who become carriers is inversely related to their age at infection. Persons who are HBV DNA positive are highly infectious.

Susceptibility & resistance

All non immune people are susceptible to infection. Immunity conferred through infection confers lifelong immunity in those who do not become chronic carriers.

Control measures

Preventive measures
Universal vaccination for hepatitis B is part of the Australian Standard Vaccination Schedule. All children are offered a birth dose which should be given within the first seven days after birth and thereafter the infant should receive hepatitis B vaccine at 2, 4 and 12 months of age.

For those not immunised in childhood, the ASVS recommends all pre-adolescent children aged 10–13 years receive hepatitis B vaccine. This is carried out in Year 7 of school. These children receive two doses of adult formulation hepatitis B vaccine.

Health care workers should ascertain their HBV immune status, particularly those engaging in invasive procedures. If infected, health care workers should consult with a medical practitioner to review and consider modifications to their work practices to reduce the risk of transmission to others in accordance with the guidelines of their relevant professional registration boards. Non-immune health care workers should be vaccinated against HBV.

Control of case
All newly acquired cases should be interviewed to identify likely risk factors for their infection and to identify others who may be at risk of infection. If the patient’s history suggests nosocomial transmission such as a surgical procedure, or other possible source of infection that may put the general public at risk such as a commercial tattoo, the Department of Human Services should be contacted for further advice and investigation.

Isolation of HBV positive patients is not required. The infected person should be educated about transmission routes, safe injecting and sexual practises, blood and body fluid precautions, and not donating organs or blood.

Control of contacts
Non-immune sexual contacts should be offered hepatitis B immunoglobulin (HBIG) 400 IU IM within 14 days of contact and commence hepatitis B vaccination.

Household contacts should be tested for HBsAg and anti-HBc and offered vaccination if susceptible.

Infants born to HBsAg positive mothers should be given a single dose of HBIG and vaccine within 12 hours of birth, at different sites. The remaining doses of vaccine should be given at 2, 4 and 12 months of age.

Recipients of needle-stick injuries should be considered for hepatitis B immunoglobulin (see Appendix 4).

Control of environment
Appendix 5 outlines procedures for dealing with spills of blood and body fluids.

Outbreak measures

Special settings - Health care workers
Registration boards should be consulted in relation to their policies regarding health care workers with blood-borne viruses. For example, the Medical Practitioners Board of Victoria has a policy on medical practitioners and medical students who carry a blood-borne virus which is available at the Medical Practitioners Board of Victoria website. Recommendations are also included in Infection control guidelines for the prevention of transmission of infectious diseases in the health care setting, at the Australian Government Department of Health and Ageing website.