Hepatitis B is a viral infection that primarily targets the liver, causing inflammation and potentially severe long-term damage. The hepatitis B virus (HBV) represents a significant global health concern, with hundreds of millions of people living with chronic infection worldwide. This virus is highly infectious, estimated to be 50 to 100 times more transmissible than the human immunodeficiency virus (HIV).
Acute vs. Chronic Hepatitis B: The Disease Lifecycle
The body’s response determines whether the infection is classified as acute or chronic. Acute infection is the initial phase following exposure, typically lasting less than six months. Most healthy adults who contract HBV clear the virus successfully, leading to complete recovery and lifelong immunity. During this acute period, the body produces specific antibodies that eliminate the virus.
Chronic hepatitis B is defined by the persistence of the virus for six months or longer. This is significantly more common when HBV is acquired during infancy, as the newborn immune system is less capable of mounting an effective response. The continued presence of the virus leads to progressive liver inflammation and scarring, known as fibrosis. Over many years, this process can advance to cirrhosis, which impairs liver function, and increases the risk of developing hepatocellular carcinoma, a type of liver cancer.
Modes of Transmission
The Hepatitis B virus is transmitted through contact with infectious bodily fluids, including blood, semen, and vaginal fluids. Transmission routes vary, but three main pathways account for the majority of new infections. The most common route globally is perinatal transmission, where the virus is passed from an infected mother to her child during birth. Without intervention, the risk of transmission can be substantial.
Sexual contact remains a major mode of spread, particularly among adults. Unprotected intercourse allows for the exchange of virus-containing fluids between partners. The third primary route involves percutaneous exposure, meaning contact with contaminated blood through the skin. This can occur through sharing needles for injecting drugs, accidental needle-stick injuries in healthcare settings, or the use of unsterilized equipment for tattooing and piercing.
Household exposure is also possible through contact with open sores or shared items like razors or toothbrushes that may have traces of infected blood. HBV is not spread through casual contact, such as sneezing, coughing, hugging, sharing food or water, or breastfeeding. The virus requires direct entry into the bloodstream or mucous membranes to establish an infection.
Symptoms and Diagnostic Testing
Many individuals, particularly those with chronic infection, remain asymptomatic and are unaware they carry the virus. When symptoms appear during the acute phase, they typically manifest one to four months after exposure. Common signs include jaundice (yellowing of the skin and eyes), fatigue, abdominal discomfort, and a loss of appetite. Other presentations may involve dark urine, joint pain, or nausea and vomiting.
Confirming the presence of the virus requires specific blood tests, known as serology, which detect viral components and the body’s immune response. The Hepatitis B surface antigen (HBsAg) is a central marker indicating current infection and infectiousness. If HBsAg remains detectable for more than six months, the infection is classified as chronic.
Another important test is the Hepatitis B surface antibody (anti-HBs), which signifies recovery from an infection or successful vaccination, providing protective immunity. The Hepatitis B core antibody (anti-HBc) indicates past or current exposure to the virus. A specific type, IgM anti-HBc, is used to confirm a very recent, acute infection. These test results provide healthcare providers with a clear picture of a person’s infection status, allowing them to differentiate between active infection, recovered infection, and immunity.
Treatment, Monitoring, and Prevention
The approach to managing hepatitis B infection depends on whether the disease is acute or chronic. For acute HBV infection, no specific antiviral treatment is typically given, as the body generally clears the virus on its own. Care focuses on supportive measures, such as managing symptoms, ensuring proper nutrition, and preventing dehydration. In rare instances where acute infection leads to severe liver failure, specialized medical intervention may be necessary.
For chronic hepatitis B infection, the goal shifts to long-term viral suppression and the prevention of liver damage. Antiviral medications, primarily nucleoside and nucleotide analogues, inhibit the virus’s ability to replicate, thereby lowering the viral load in the blood. First-line drugs often include tenofovir or entecavir, which have high potency and a low rate of drug resistance. While these treatments slow the progression to cirrhosis and reduce the risk of liver cancer, they must often be taken long-term as they do not typically cure the infection.
Individuals living with chronic HBV infection require consistent monitoring to assess liver health and treatment effectiveness. Regular check-ups involve blood tests to measure liver enzyme levels, which indicate inflammation, and to quantify the amount of HBV DNA in the blood. Imaging techniques, such as ultrasound, may also be used periodically to check for signs of advanced scarring or the development of liver tumors. Early detection of complications offers the best chance for successful intervention.
The most effective strategy against hepatitis B is prevention, centered on the use of a highly effective vaccine. The hepatitis B vaccine is considered the first anti-cancer vaccine because it prevents the infection that causes most liver cancers worldwide. It offers nearly 100% protection and is administered as a series of injections over several months. The World Health Organization recommends that all infants receive their first dose within 24 hours of birth to prevent chronic infection associated with early-life exposure.
Vaccination is also recommended for all children, adolescents, and adults who were not previously immunized. Prevention involves practicing safer behaviors, such as using barrier protection during sexual activity and avoiding the sharing of needles or any personal items that may have come into contact with blood. For infants born to infected mothers, a combination of the vaccine and Hepatitis B Immune Globulin (HBIG) given immediately after birth provides robust protection against transmission.