Hepatitis B
Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease. The virus can be spread through contact with blood or other body fluids during sex with an infected partner, unsafe injections, or exposures to sharp instruments. However, most commonly, transmission happens from mother to child during birth and delivery.
In highly endemic areas, hepatitis B can spread through horizontal transmission, especially from an infected child to an uninfected child during the first five years of life. That's why in many countries, newborns are vaccinated against hepatitis B. Hepatitis B can be almost 100% prevented by vaccines that are safe, available, and effective.
Hepatitis B is also spread by needle stick injury, tattooing, piercing, and exposure to infected blood and body fluids such as saliva, menstrual, vaginal, and seminal fluids. Sexual transmission is more prevalent in unvaccinated persons with multiple sexual partners. Acquiring hepatitis B in childhood is more dangerous because hepatitis B infection acquired in adulthood leads to chronic hepatitis in less than five percent of cases, whereas infection in infancy and early childhood leads to chronic hepatitis in about 95 percent of cases.
The hepatitis B virus can survive outside the body for at least seven days. During this time, the virus can still cause infection if it enters the body of a person who is not protected by the vaccine. The incubation period of the hepatitis B virus ranges from 30 to 180 days, but the virus may be detected in the blood within 30 to 60 days after infection. Most people do not experience any symptoms when newly infected.
Acute Symptoms
Most people do not have any symptoms, but when symptoms do occur, they include yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting, and abdominal pain. People with acute hepatitis can develop acute liver failure, which can lead to death, but such cases are rare. More than 95 percent of people who become infected as adults or older children will stage a full recovery and develop protective immunity to the virus.
Long-term complications include a subset of persons who develop advanced liver diseases such as cirrhosis and hepatocellular carcinoma, which cause high morbidity and mortality. The tests called assays for detection of hepatitis B virus infection involve serum or blood tests that detect either viral antigens (proteins produced by the virus) or antibodies produced by the host. The hepatitis B surface antigen (HBsAg) is most frequently used to screen for the presence of this infection.
Acute hepatitis B infection does not usually require treatment, and most adults clear the infection. Early antiviral treatment may be required in fewer than one percent of people whose infection takes a very aggressive course, such as fulminant hepatitis or who are immunocompromised. Chronically infected individuals with persistently elevated serum alanine aminotransferase (a marker of liver damage) may require treatment.
There is no specific treatment for acute hepatitis B; therefore, care is aimed at maintaining comfort and adequate nutritional balance, including replacement of fluids lost from vomiting and diarrhea. Most important is the avoidance of unnecessary medications. Acetaminophen (paracetamol) and medication against vomiting should be avoided.
As of 2018, there are eight medications licensed for the treatment of hepatitis B infection in the United States. These include antiviral medications: lamivudine, adefovir, tenofovir disoproxil, tenofovir alafenamide, telbivudine, and entecavir, as well as the two immune system modulators, interferon alpha-2a and pegylated interferon alpha-2a. Treatment lasts from six months to one year. Treatment can slow the progression of disease, reduce the incidence of liver cancer, and improve long-term survival.
The WHO recommends that all infants receive the hepatitis B vaccine as soon as possible after birth, preferably within 24 hours, followed by two or three doses of hepatitis B vaccine at least four weeks apart to complete the vaccination series. Protection lasts at least 20 years and is probably lifelong. The disease is most common in the Western Pacific (6.2%) and African (6.1%) regions. In Europe, rates are 1.6%, and in the Americas, they are 0.7%.