Hepatitis B

Overview

Hepatitis B is an infection of the liver caused by the hepatitis B virus (HBV). HBV is a DNA virus belonging to the Hepadnavirus family.

Hepatitis B can be prevented with vaccination.

Disease epidemiology

HBV universal vaccination was introduced in Singapore on 1 September 1987. The prevalence of HBsAg among children and adolescents aged 5 to 17 years was 0.4% in a seroprevalence study conducted between 2008 and 2010. The overall HBsAg prevalence among Singapore residents aged 18 to 69 years was 3.6% in 2010, corresponding to an intermediate prevalence area as defined by WHO.

In Singapore, a total of 44 cases of acute HBV infections were reported in 2020.

Pathogen(s)

Hepatitis B virus (HBV).

Transmission

HBV is transmitted from person-to-person via blood or body fluids. Recognised modes of transmission include mother-to-child transmission, blood transfusion, nosocomial infection, sharing of needles, and sexual transmission.

The predominant mode of transmission of HBV depends on the prevalence. Mother-to-child transmission is the major route of transmission in high-prevalence areas, while injection drug abuse and unprotected sexual intercourse are the predominant mode of transmission in low prevalence countries.

Incubation period: 1 to 4 months.

Infectious period: From 2 weeks before the onset of jaundice until the patient becomes surface antigen negative.

Clinical features

In adults, approximately 70% with acute HBV infection are asymptomatic. The remaining 30% may experience a prodromal serum-sickness-like phase followed by constitutional symptoms such as jaundice, nausea, malaise, and right upper quadrant pain.

Fulminant hepatic failure is uncommon, occurring in about 0.1% to 0.5% of patients. There is increased risk of fulminant or more severe hepatitis in patients who are co-infected with other hepatitis viruses and HIV, took acetaminophen during the illness or who are drug abusers, especially methamphetamine.

Neonates with HBV infection rarely show clinical features or transaminitis at birth. A small number develop acute hepatitis by two months of age, presenting with jaundice and elevated liver enzymes.

Risk factors

Risk factors include:

• Unprotected sex with an infected person

• Having multiple sex partners

• Inconsistent condom use if the relationship is not monogamous

• History or current presence of other STIs

Men who have sex with men (MSM) and intravenous drug users (IVDU) are considered at risk groups for HBV acquisition. HBV is also endemic in Southeast Asia therefore vaccination is recommended for the general population.

Diagnosis

The order of appearance of markers in acute infections is HBsAg, HBeAg, anti-HBc IgM, anti-HBe, anti- HBc IgG, anti-HBs. Acute HBV infection is diagnosed when HBsAg and anti-HBc IgM is detected.

Treatment and management

Treatment should normally be given in collaboration with a hepatologist, or physician experienced in the management of liver disease.

Patients should be advised to avoid unprotected sexual intercourse until they have become non-infectious or their partners have been successfully vaccinated. They should also be screened for other STIs in cases thought to have been sexually acquired or if otherwise appropriate.

For most patients with acute HBV infection, treatment is mainly supportive. In immunocompetent adults, less than 1% develop liver failure, while less than 5% progress to chronic HBV infection.

In patients with severe liver disease such as those with coagulopathy, marked jaundice or with persistent symptoms, tenofovir or entecavir can be used as monotherapy until the patient has cleared HBsAg (two tests done, four weeks apart).

Pregnancy considerations and breastfeeding:

The risk of vertical transmission of HBV from HBsAg positive mothers is as high as 90% in women who are HBeAg positive. This risk is about 30% in HBeAg negative mothers.

New-borns of mothers who test positive for HBsAg should receive both passive and active immunisation (using hepatitis B specific immunoglobulin) within 12 hours of delivery at different sites. Infants should go on to complete the whole HBV immunisation series. Even with passive-active immunisation, children born to HBeAg positive mothers remained at risk of transmission, at about 9%.

Infants who received HBV active-passive immunisation at birth can be breastfed. The infant should complete the hepatitis B vaccine series. However, for mothers who require antiviral treatment, the safety of antiviral therapy during breastfeeding is currently unclear.

Refer to the Department of Sexually Transmitted Infections Control (DSC)'s website for more information on HBV treatment. 

Precaution, prevention, and control

HBV screening should be considered in MSM, sex workers, injecting drug users, HIV-positive patients, sexual assault victims, needle-stick victims and sexual partners of positive or high-risk patients.

All pregnant women should also be tested for HBV during their first prenatal visit and thereafter, if there is risk of infection from their regular partner.

Prevention of hepatitis B:

• Vaccination against hepatitis B is recommended by the CDC for all infants, all children, or adolescents aged younger than 19 years who have not been vaccinated, all adults aged 19 through 59 years, and adults aged 60 years or older with risk factors for hepatitis B infection.

• All infants should receive the hepatitis B vaccine as soon as possible after birth (within 24 hours). This is followed by two or three doses of hepatitis B vaccine at least four weeks apart.

• To reduce the risk of getting HBV:

  • Using condoms and consistently and correctly when engaging in sexual activity.

  • Limit the number of sex partners.

  • Avoid sharing needles or any equipment used for injecting drugs, piercing, or tattooing.

  • Routine use of standard precaution when handling blood or bodily fluids.

Management of sexual contacts:

Partner notification should be performed and documented, and its outcome documented at the follow-up. Contact tracing should include any sexual contact or needle-sharing partners during the period in which the index case is thought to have been infectious.

The infectious period is from two weeks before the onset of jaundice until the patient tests surface antigen negative. In cases of chronic infection trace contacts as far back as any episode of jaundice or to the time when the infection is thought to have been acquired, this may be impractical for periods of longer than two or three years.

Notification

Acute hepatitis B is a notifiable disease.

Who should notify:

• Medical practitioners

• Laboratories

When to notify:

• On clinical suspicion or laboratory confirmation

How to notify:

• Please refer to the Infectious Disease Notifications for more information.

Notification timeline:

• Within 72 hours from time of diagnosis

Resources

Refer to the Resources page for the communicable disease surveillance in Singapore.

Refer to DSC’s website for more information on HBV infection.

References

• Centers for Disease Control and Prevention. STI treatment guidelines: Hepatitis B virus (HBV) infection. 2021.

• Department of Sexually Transmitted Infections Control (DSC). STI management guidelines 7^th edition. 2021.

• World Health Organization. Hepatitis B. 2023.