Hepatitis B is inflammation of the liver caused by infection with the hepatitis B virus. This highly contagious virus is spread through exposure to bodily fluids infected with the virus including blood, semen, breast milk, vaginal secretions and saliva.
The hepatitis B virus is between 50 and 100 times more infectious than HIV and can also survive outside of the body for at least a week, meaning surfaces or objects contaminated with dried blood, for example, can also pose a risk.
Hepatitis B is the most common form of hepatitis found worldwide, although it is uncommon in the U.K. Regions where incidence of this condition is higher include Asia, sub-Saharan Africa, the Middle East, and southern Europe. In the inner cities of these regions, up to one in 60 pregnant women may be infected with the virus.
The incubation period of hepatitis B is 22 weeks, during which time infected individuals may present with few or no symptoms. However, these individuals are still contagious and capable of unknowingly transmitting the virus to others.
Symptoms
The symptoms caused by hepatitis B range in severity from mild to life threatening. The illness can occur as either an acute or chronic disease. Acute hepatitis B is a short-term illness that occurs within six months of exposure to the virus and is usually cleared by adults within three months (in 90% of cases). Individuals who recover also develop antibodies against any future hepatitis B infection.
Infants, on the other hand, are less resilient to hepatitis B because their immune systems do not launch an attack against the virus that is vigorous enough to clear it. In 90% of cases, infected infants go on to develop the chronic form of hepatitis B. By contrast, only 6 to 10% of children older than five years go on to develop chronic illness. Up to one in ten adults who become infected with hepatitis B also go on to develop chronic disease.
Acute hepatitis
Not all individuals infected with the hepatitis B virus develop the symptoms of acute hepatitis, with around 30% of those infected staying symptom-free. In cases where symptoms do develop, they occur between 40 and 160 days after infection and tend to pass within three months. These early symptoms are non-specific and include the following:
- Flu-like symptoms such as weakness, body aches, headache, and a temperature of 38ºC (100.4ºF) or above
- Loss of appetite
- Nausea and vomiting
- Diarrhea
- Fatigue
Sometimes, the symptoms of acute hepatitis B can be more severe and the patient requires hospitalization. Examples of more severe symptoms include:
- Dark urine
- Pale stool
- Jaundice (yellowing of the skin and whites of the eyes)
In rare cases, the liver damage caused by acute hepatitis is so severe that the organ can no longer function. This fatal condition is referred to as “fulminant hepatitis” and can lead to severe bleeding disorders and coma. Patients suffering from this condition are usually evaluated for liver transplantation.
Chronic hepatitis B
In cases where the immune system fails to control hepatitis B within six months, an individual is said to have chronic hepatitis B. Again, not everyone with the chronic form of this disease develops symptoms. The liver plays a key role in many vital bodily functions, including immunity, coagulation, digestion and metabolism. Symptoms therefore vary widely depending on how severe the liver damage is and how much dysfunction has been caused.
Cirrhosis
Individuals with chronic hepatitis B can remain symptom-free for many years or even decades. However, in some cases, inflammation of the liver can cause severe scarring of the organ referred to as cirrhosis, which can eventually lead to liver dysfunction. Some of the symptoms that suggest cirrhosis may have developed include:
- Fatigue and weakness
- Loss of appetite
- Weight loss
- Enlarged breasts in men
- Rash on the palms of the hands
- Poor coagulation
- Spider-like blood vessels on the skin
- Increased susceptibility to infection
In cases of advanced cirrhosis, liver failure can occur, which may lead to the following life-threatening complications:
- Inability of the liver to clear toxic substances can lead to confusion and even coma.
- Pressure may rise in the portal vein that carries blood to the liver from the bowel and spleen. Referred to as portal hypertension, this causes fluid to accumulate in the abdominal cavity (ascites) and the formation of esophageal varices that are at risk of tearing and causing internal bleeding.
- Another complications of portal hypertension is spleen enlargement, which can lead to anemia, as well as raising the risk of infection and bleeding.
- A reduction in the number of coagulation factors produced by the liver can lead to blood clotting disorders and sometimes spontaneous bleeding.
- The liver may fail to eliminate bilirubin, which causes jaundice to develop.
Liver cancer
Individuals with chronic hepatitis B are at an increased risk of developing liver cancer. The symptoms are non-specific and again range in severity. Some patients have no symptoms; some experience inflammation and pain; while others may experience fever and weight loss.
The condition is diagnosed using an ultrasound scan of the liver and a blood test to check for alpha-fetoprotein, which is produced in cases of liver cancer. Patients who have chronic hepatitis B are screened using these two tests, particularly if they have developed cirrhosis or have a family history of liver cancer.
Further Reading
Great ape museum specimens reveal secrets of DNA virus evolution