Hepatitis B is an infectious disease caused by the Hepatitis B virus (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection.Many people have no symptoms during an initial infection. For others, symptoms may appear 30 to 180 days after becoming infected and can include a rapid onset of sickness with nausea, vomiting, yellowish skin, fatigue, dark urine, and abdominal pain. Symptoms during acute infection typically last for a few weeks, though some people may feel sick for up to six months. Deaths resulting from acute stage HBV infections are rare. An HBV infection lasting longer than six months is usually considered chronic. The likelihood of developing chronic hepatitis B is higher for those who are infected with HBV at a younger age. About 90% of those infected during or shortly after birth develop chronic hepatitis B, while less than 10% of those infected after the age of five develop chronic cases. Most of those with chronic disease have no symptoms; however, cirrhosis and liver cancer eventually develop in about 25% of those with chronic HBV.The virus is transmitted by exposure to infectious blood or body fluids. In areas where the disease is common, infection around the time of birth or from contact with other peoples blood during childhood are the most frequent methods by which hepatitis B is acquired. In areas where the disease is rare, intravenous drug use and sexual intercourse are the most frequent routes of infection.
In the United States, an estimated 0.26% of the population was living with HBV infection as of 2018. History
Findings of HBV DNA in ancient human remains have shown that HBV has infected humans since at least ten millennia, both in Eurasia and in the Americas. This disproved the belief that hepatitis B originated in the New World and spread to Europe around 16th century. Hepatitis B virus subgenotype C4 is exclusively present in Australian aborigines, suggesting an ancient origin as much as 50,000 years old. However, analyses of ancient HBV genomes suggested that the most recent common ancestor of all known human HBV strains was dated to between 20,000 and 12,000 years ago, pointing to a more recent origin for all HBV genotypes. The evolution of HBV in humans was shown to reflect known events of human history such as the first peopling of the Americas during the late Pleistocene and the Neolithic transition in Europe. Ancient DNA studies have also showed that some ancient hepatitis viral strains still infect humans, while other became extinct.The earliest record of an epidemic caused by hepatitis B virus was made by Lurman in 1885. An outbreak of smallpox occurred in Bremen in 1883 and 1,289 shipyard employees were vaccinated with lymph from other people. After several weeks, and up to eight months later, 191 of the vaccinated workers became ill with jaundice and were diagnosed with serum hepatitis. Other employees who had been inoculated with different batches of lymph remained healthy.