About HBV

As an expert in his field, Prof. Patrick Kennedy has dedicated his time to Hepatitis B research, teaching and speaking internationally on the subject.


What Is Hepatitis B?

Hepatitis B virus (HBV) is the most common chronic viral infection worldwide; approximately one-third of the world’s population have evidence of prior exposure; and over 250 million people have chronic hepatitis B (CHB). The liver is the site of infection, consequently HBV is a leading cause of chronic liver disease, cirrhosis and liver cancer; the complications of chronic infection account for an estimated 700,000 deaths per year globally.

Hepatitis Explained

Hepatitis describes inflammation of the liver, which is usually detected by abnormal liver function tests. For this reason, elevated or abnormal liver enzymes warrants further investigation. Hepatitis B virus is one of many causes of abnormal liver tests. The presence of liver inflammation and it’s persistence over time can result in serious liver disease, the spectrum of which includes:

Fibrosis – a build-up of scar tissue, which is broadly classified as mild, moderate or severe

Cirrhosis – is the severe form of liver scarring, which is associated with changes in blood flow into and through the liver and is associated with impaired liver function 

Hepatocellular carcinoma (HCC) – is the most common form of liver cancer, which usually arises from a scarred or cirrhotic liver

End-stage liver disease – severe loss of liver function that can result in death without a liver transplant.

How Is Chronic Hepatitis B (CHB) Diagnosed?

A simple blood test can diagnose CHB. The presence of Hepatitis B surface antigen (HBsAg) is the hallmark of chronic infection. Anyone found to be HBsAg positive, should be referred to specialist care.  



How Is HBV Transmitted?

HBV is transmitted through blood and body fluids, therefore it can be transmitted through sexual contact, sharing of needles, syringes or other drug paraphernalia, but also tooth brushes and razors. Direct contact with the blood or open sores of an infected individual or similarly the exposure to blood from needlesticks or other “sharp injuries” from an infected individual can result in transmission. In high prevalence regions, the majority of HBV infections are through vertical (or perinatal) transmission, which means the spread of HBV from an infected mother to her child at birth or around the time of birth.


Prevalence rates of CHB infection vary widely, from 5-10% in high endemic areas such as sub-Saharian Africa, East Asia, the Amazon and the Southern regions of Eastern and Central Europe. However, in Western Europe and North America <1% of the adult population is chronically infected.  Notably, in recent years prevalence in individual countries appears to be influenced by migration patterns with immigrants accounting for 95% of new diagnoses of HBV infections in many developed countries.


What Are The Symptoms Of HBV Infection?

HBV can cause of acute viral Hepatitis and the following signs and symptoms can be present; abdominal pain, loss of appetite, nausea and vomiting. Fever, general malaise, weakness, fatigue and in a proportion, joint pains. While many of the symptoms associated with acute HBV are similar to those of “flu”, the development of jaundice (yellowing of the skin or whites of the eyes) and the presence of dark urine should raise the suspicion of acute viral hepatitis.


The majority of HBV infections in adulthood lead to an acute illness, which lasts for less than 6 months. Adult infection is associated with a robust immune response in the majority of cases  (>95%), which can clear the virus from the body leading to resolved HBV infection. In a small proportion of adults ~ 5%, chronic HBV can develop.


When HBV is transmitted from mother to child (at birth) or horizontally in early childhood, the majority ~ 90% will develop chronic hepatitis B (CHB) infection. Chronic infection is defined by the presence of HBsAg in the blood for more than 6 months and in the majority of cases, chronic infection is lifelong. CHB is often asymptomatic and may go undetected for many years. In some cases, chronic infection can present late with the complications of CHB, namely cirrhosis and liver cancer. This underlines the importance of early testing and the detection of HBV.



Where Is Hepatitis Most Common?

The highest rates of CHB infection are concentrated in Asia, Africa and South America with up to 10% of the population in these areas affected. In Eastern Europe and North Africa, infection rates are as high as 7%. 

In the UK the rate of chronic infection is considerably lower, however, it is estimated that up to 500,000 people may be infected with CHB nonetheless. In other parts of Western Europe, the USA and Australia, prevalence rates are reported between 1 & 2%. 

The mosts affected areas of the world are concentrated in Asia, Africa and South America. In some cases up to 25% of the population in these areas suffer with chronic hepatitis B. In Eastern Europe some areas of South American and North Africa infections rates are as high as 7%.

In the UK the rate of infection is considerably lower, however still evident. Around 200,000 people are infected by Hepatitis B and undergo regular drug therapies. In other areas of Western Europe, the USA and Australia, less than 2% of the population are infected.




The Hepatitis B Vaccine

All babies should be vaccinated at birth as a public health measure to prevent further transmission of the virus and the development of CHB. In addition, adults who are known to be at risk should be screened and vaccinated

The vaccine for Hepatitis B is usually given in three doses. After the first vaccine, the second is given within a month and the third is administered 5 months later. It is recommended to undergo a blood test after vaccination to ensure the vaccine has worked and the antibody titer (or level) is satisfactory. As immunity can diminish with time, the antibody titer can be measured and a booster administered if necessary.  

Hepatitis B And Pregnancy

As vertical transmission from mother to child is a leading cause of CHB globally, it is critical to screen all pregnant mothers for Hepatitis B and offer appropriate management to both the mother and her unborn child. While the majority of women found to have CHB during pregnancy will not require any treatment over the course of their pregnancy, it is imperative that these women are under specialist care in order to offer appropriate care to their children, the mainstay of which is vaccination, and for their future care.

A proportion of women found to have CHB in pregnancy will have high levels of virus (HBV DNA); in these women antiviral therapy will be mandated in the later stages of pregnancy to reduce the risk of transmission to their child. Furthermore, their newly born will need specific therapy (hepatitis B immunoglobulin) in addition to vaccination to minimise the risk of HBV transmission.

The diagnosis of CHB during pregnancy should also act as a trigger to test partners, other family members or household contacts, all of whom will also be at risk of CHB. Anyone found to be HBsAg positive should be referred to specialist care and those who test negative, should be offered vaccination if appropriate.    

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