Hepatitis B
What is hepatitis B?
Hepatitis B is a viral infection that is caused by the hepatitis B virus (HBV) and results in inflammation of the liver and liver disease (e.g. cirrhosis and liver cancer). The World Health Organization (WHO) estimated that 254 million people were living with chronic hepatitis B infection in 2022.
Is hepatitis B a notifiable disease?
Hepatitis B is a notifiable disease under the Infectious Disease Regulations. All cases should be notified to the Medical Officer of Health, including those identified by laboratories, migrant screening programmes and through STI screening programmes and GUM clinics. HPSC reports describing hepatitis B notifications and epidemiology are available here: https://www.hpsc.ie/a-z/hepatitis/hepatitisb/surveillancereports/
Where is hepatitis B a problem?
Countries are classified as having low, intermediate, or high hepatitis B prevalence based on the percentage of the population positive for infection (shown by being positive for hepatitis B surface antigen (HBsAg) on a blood test).
Ireland, most countries in Western Europe, the United States, Canada, and Australia have a low hepatitis B prevalence (<2% HBsAg). Most countries in the Caribbean, South America, Central Europe, Eastern Europe, North Africa, and the Middle East have intermediate levels of hepatitis B (2-7% HBsAg). Many countries in Sub-Saharan Africa, and in East, South and South-East Asia, have high levels of hepatitis B (≥8% HBsAg).
In low prevalence countries like Ireland, most infections are acquired sexually. In high prevalence countries, hepatitis B is commonly spread from mother to child at birth or is acquired through exposure to infected blood from another child or family member in early childhood. Transmission in healthcare settings may also occur more commonly in countries where infection prevention control precautions are not adequately followed.
How is hepatitis B spread?
Hepatitis B is spread when blood, semen or other body fluids from an infected person enter the body of a person who is not immune. This occurs in a variety of ways, including sexual contact with an infected person, transmission from an infected mother to her baby around the time of birth, sharing of needles and other drug equipment by people who inject or snort drugs, and sharing items that can break skin or mucous membranes (e.g. razors, toothbrushes, glucose monitoring equipment).
Poor infection control practises in healthcare settings (e.g. dialysis units, diabetes clinics) and needlestick injuries can also spread hepatitis B.
You cannot get hepatitis B from sneezing, coughing, kissing, hugging, sharing cutlery or dishes, food, or water.
Who is most at risk of hepatitis B infection?
Although anyone can get hepatitis B, there are certain groups of people who are more at risk of getting infected. These include:
• Infants born to HBsAg positive mothers (current infection with hepatitis B)
• Those born in, or travelling to, countries with intermediate or high hepatitis B prevalence
• Gay, bisexual, and other men who have sex with men (gbMSM)
• People with multiple sexual partners
• Those living in a household with an infected person
• People who use drugs
• People with occupational risk of exposure e.g. healthcare workers
• People with medical conditions that increase risk of exposure (e.g. on dialysis, diabetes, require blood transfusions)
• People experiencing homelessness
What is the incubation period for hepatitis B?
The incubation period (time from infection to onset of symptoms) is 6 weeks to 6 months, the average being 2 to 3 months.
What are the symptoms of hepatitis B infection?
Not everyone with acute HBV infection will have symptoms. In fact, only 30 to 50% of adults and 10% of children develop symptoms when they are first infected. These symptoms include:
- Fever
- Fatigue
- Nausea and vomiting
- Loss of appetite
- Abdominal pain
- Dark urine
- Clay-coloured stools
- Jaundice
- Joint pain
In those with symptomatic acute hepatitis B infection, symptoms last from a few weeks to several months.
What are the complications of chronic hepatitis B?
Chronic (long-term/lifelong) infection occurs in around 80-90% of infants infected in their first year of life, 30-50% of children infected before the age of 6 years, and <10% of people infected as adults.
Those who develop chronic infection are at increased risk of developing:
- Chronic hepatitis (ongoing inflammation of the liver)
- Cirrhosis (scarring of the liver)
- Primary hepatocellular carcinoma (liver cancer)
This liver damage usually occurs gradually over 20-40 years and people with chronic infection may have mild symptoms or no symptoms for a long time. Premature death from chronic liver disease occurs in 15-25% of chronically infected people.
How is hepatitis B diagnosed?
Hepatitis B is diagnosed by testing the patient's blood for the presence of specific viral antigens (HBsAg) or by nucleic acid testing (PCR test for hepatitis B DNA).
Specific tests might also be used to assess for the presence and extent of liver disease. This includes a physical examination, blood tests, and imaging scans.
Can hepatitis B be treated?
There is no specific treatment for the acute hepatitis B infection. Therapy should be supportive and aimed at maintaining adequate nutritional balance.
Chronic hepatitis B infection can be treated antiviral medications. The aim of this treatment is to slow the occurrence and progression of liver disease, as well as to improve long-term survival. However, eradication of the hepatitis B virus is rare in those who become chronically infected, and treatment is usually lifelong. As a result, people with chronic hepatitis B infection should avoid alcohol and should ensure they are immunised against hepatitis A infection.
HIV coinfection creates challenges when it comes to treating hepatitis B. However, antiretroviral therapies (ART) are available that are active against both infections. For more information, visit WHO’s Guidelines for the prevention, diagnosis, care and treatment for people with chronic hepatitis B infection or EASL Clinical Practice Guidelines on the management of hepatitis B virus infection.
How can hepatitis B infection be prevented?
Hepatitis B infection can be prevented in different ways:
- There is a safe and effective vaccine for hepatitis B. Universal infant vaccination was introduced in Ireland in 2008. Infants receive 3 doses of the hepatitis B vaccine through the Irish Childhood Immunisation Schedule.
- Vaccination is also recommended for people at higher risk of infection (see below for more information)
- Use of standard precautions when handling human blood and body fluids and in situations where skin piercing equipment is used
- Screening of blood donors for hepatitis B
- Use of safe sex practices
- Needle exchange programmes for people who inject drugs
Hepatitis B vaccination
Hepatitis B is preventable with a vaccination. All those at increased risk of hepatitis B should receive the vaccination:
- Occupational risk of exposure to blood or blood-contaminated environments
- Family and household contacts
- Those who inject or snort drugs, and their contacts
- Those at risk due to medical conditions (e.g. HIV, chronic kidney or liver disease, those that require frequent blood transfusions)
- Gay, bisexual, and other men who have sex with men (gbMSM)
- Those with multiple sexual partners / who change partners frequently
- Travellers to, or from, areas with a high or intermediate prevalence of hepatitis B virus
Hepatitis B can be passed from mother to child during birth. As a result, pregnant women should be screened for infection, and if a pregnant woman is hepatitis B positive, she might be asked to take antiviral medications during her pregnancy. Regardless of whether she takes this medication, all babies born to mothers with hepatitis B should receive a birth dose of the vaccine and hepatitis B immunoglobulin (HBIG) within 12 hours of delivery.
Last updated: 21 July 2025