Hepatitis B

Notification requirement for hepatitis B

Hepatitis B infection is a ‘routine’ notifiable condition and must be notified by medical practitioners and pathology services in writing within 5 days of diagnosis.

This is a Victorian statutory requirement.

Primary school and children’s services centre exclusion for hepatitis B

Exclusion is not applicable.

Infectious agent of hepatitis B

Hepatitis B virus (HBV), a double-stranded DNA virus, is the causative agent.

Identification of hepatitis B

Clinical features

Less than 10 per cent of children and only 30–50 per cent 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, light stools and jaundice. The severity of infection ranges from asymptomatic cases, detected only after investigation of abnormal liver function tests, to fulminant and often fatal cases with extensive acute hepatic necrosis. The case-fatality rate is about 1 per cent and is higher in those over 40 years of age.

Chronic HBV infection is found in 0.5–1 per cent of adults in Australia and up to 20 per cent elsewhere. Prevalence in Aboriginal and Torres Strait Islander populations is among the highest in the world at between 4 per cent and 26 per cent, depending on the region. After acute HBV infection (which may be asymptomatic), the risk of developing chronicity varies with age: 90 per cent for people infected at birth, 20–50 per cent for people infected at 1–5 years, and 1–10 per cent for people infected as older children or adults. Chronic infection is common in those with immunodeficiency. Premature death secondary to cirrhosis/hepatocellular carcinoma (HCC) occurs in 15–20 per cent. The risk of HCC remains elevated lifelong, even in patients who do not develop cirrhosis.

Diagnosis

HBV infection is confirmed by the detection of hepatitis B surface antigen (HBsAg) or 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 past 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 IgM HBcAg in the absence of prior evidence of HBV infection.

Serology for chronic infections requires:

• detection of HBsAg or HBV DNA in the serum of a patient on two occasions at least 6 months apart.

Table 1 summarises the interpretation of hepatitis B virus serology.

Table 1: Interpretation of hepatitis B virus serology

Source: Centers for Disease Control and Prevention

*1. May be recovering from acute HBV infection

2. May be distantly immune and the test is not sensitive enough to detect very low level of anti-HBs in serum

3. May be susceptible with a false positive anti-HBc

4. May be undetectable level of HBsAg present in the serum, and the person is actually chronically infected

5. Maternal antibody

Incubation period of hepatitis B virus

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

Public health significance and occurrence of hepatitis B

HBV is a major cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma.

An estimated 2 billion people have been infected with HBV worldwide, 350 million of whom have chronic infection. Each year, an estimated 1 million people die as a result of HBV infections, and more than 4 million new acute clinical cases occur.

In countries with low endemicity (HBsAg prevalence 2 percent), most infections occur in young adults, especially among people who belong to known high-risk groups in higher endemicity areas (HBsAg prevalence ≥2 per cent), 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 of hepatitis B virus

Humans are the reservoir.

Mode of transmission of hepatitis B virus

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 (intravenous, intramuscular, subcutaneous, intradermal) and permucosal exposure to contaminated blood and body fluids. This may occur during:

• sexual contact (increased risk with anal intercourse)
• birth or perinatally (vertical transmission from mother to infant, especially if HBsAg positive)
• injecting drug use (direct injection or via contaminated drug preparation equipment)
• some household activities, such as sharing razors or toothbrushes
• invasive procedures in the community, such as tattooing or body piercing, if there is inadequate infection control
• invasive medical (haemodialysis, acupuncture) or dental procedures if there is inadequate infection control
• •needlestick injury (risk of transmission from HBV-positive source is up to 63 per cent).

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

Period of communicability of hepatitis B

Transmission by infected people can occur many weeks before the onset of symptoms, throughout the acute clinical course of the disease and during the chronic state. All people who are HBsAg positive are potentially infectious, and those with detectable HBV DNA are highly infectious (especially if HBsAg positive).

Susceptibility and resistance to hepatitis B

All nonimmune people are susceptible to infection. It is thought that lifelong immunity is conferred via acute infection in those who do not become chronically infected. However, recent evidence suggests that, in spite of serological recovery (production of anti-HBc and anti-HBs antibodies), there is persistence of HBV after acute infection. Maintenance of the T-cell response is responsible for keeping the virus under control. However, reactivation or ‘flare’ can occur in the setting of immunosuppression (particularly at the time of withdrawal of immunosuppressive therapy) or other liver injury (for example, alcohol, drugs, other hepatitis viruses).

Control measures for hepatitis B

Preventive measures

Universal vaccination for hepatitis B is part of the childhood immunisation program. All children are offered the hepatitis B vaccine within 7 days of birth, and then at 2, 4 and 6 months of age.

Healthcare workers, particularly those engaging in invasive procedures, should ascertain their HBV immune status. If infected, healthcare 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. Nonimmune healthcare 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 another possible source of infection that may put the general public at risk, such as a commercial tattoo, the department 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 practices, blood and body fluid precautions, and not donating organs or blood. Referral to a liver or hepatitis clinic is advisable to discuss treatment options and organise long-term surveillance for hepatocellular carcinoma. Screening for other bloodborne or sexually acquired infections should be undertaken, as appropriate.

Control of contacts

Nonimmune sexual contacts should be offered hepatitis B immunoglobulin (HBIG) 400 IU IM within 14 days of contact, and commence the hepatitis B vaccination program at 0, 1 and 6 months. This results in protective immunity in approximately 90 per cent of people.

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 6 months of age, as per the National Immunisation Program schedule.

Recipients of needlestick injuries from an HBV-positive source should be considered for hepatitis B immunoglobulin and vaccination if they are HBV negative.

Control of environment

Health services should have procedures for dealing with spills of blood and body fluids.

Outbreak measures for hepatitis B

Registration boards should be consulted in relation to their policies regarding healthcare workers with bloodborne viruses. For example, the Medical Practitioners Board of Victoria has a policy on medical practitioners and medical students who carry a bloodborne virus. Recommendations are also included in Australian guidelines for the prevention and control of infection in healthcare at the National Health and Medical Research Council website.