A silent killer

Hepatitis B is an infectious disease caused by the hepatitis B virus (HBV) that affects the liver;[1][7] it is a type of viral hepatitis.[8] It can cause both acute and chronic infection.[1] Many people have no symptoms during the initial infection.[1] In acute infection, some may develop a rapid onset of sickness with vomiting, yellowish skin, tiredness, dark urine and abdominal pain.[1] Often these symptoms last a few weeks and rarely does the initial infection result in death.[1][9] It may take 30 to 180 days for symptoms to begin.[1] In those who get infected around the time of birth 90% develop chronic hepatitis B while less than 10% of those infected after the age of five do.[4] Most of those with chronic disease have no symptoms; however, cirrhosis and liver cancer may eventually develop.[2] Cirrhosis or liver cancer occur in about 25% of those with chronic disease.[1]

Hepatitis BElectron micrograph of hepatitis B virusSpecialtyInfectious disease, gastroenterologySymptomsNone, yellowish skin, tiredness, dark urine, abdominal pain[1]ComplicationsCirrhosis, liver cancer[2]Usual onsetSymptoms may take up to 6 months to appear[1]DurationShort or long term[3]CausesHepatitis B virus spread by some body fluids[1]Risk factorsIntravenous drug use, sexual intercourse, dialysis, living with an infected person[1][4]Diagnostic methodBlood tests[1]PreventionHepatitis B vaccine[1]TreatmentAntiviral medication (tenofovir, interferon), liver transplantation[1]Frequency>391 million (2017)[5]Deaths65,400 direct (2015), >750,000 (total)[1][6]

The virus is transmitted by exposure to infectious blood or body fluids.[1] Infection around the time of birth or from contact with other people's blood during childhood is the most frequent method by which hepatitis B is acquired in areas where the disease is common.[1] In areas where the disease is rare, intravenous drug use and sexual intercourse are the most frequent routes of infection.[1] Other risk factors include working in healthcare, blood transfusions, dialysis, living with an infected person, travel in countries where the infection rate is high, and living in an institution.[1][4] Tattooing and acupuncture led to a significant number of cases in the 1980s; however, this has become less common with improved sterilization.[10] The hepatitis B viruses cannot be spread by holding hands, sharing eating utensils, kissing, hugging, coughing, sneezing, or breastfeeding.[4] The infection can be diagnosed 30 to 60 days after exposure.[1] The diagnosis is usually confirmed by testing the blood for parts of the virus and for antibodies against the virus.[1] It is one of five main hepatitis viruses: A, B, C, D, and E.[11]

The infection has been preventable by vaccination since 1982.[1][12] Vaccination is recommended by the World Health Organization in the first day of life if possible.[1] Two or three more doses are required at a later time for full effect.[1] This vaccine works about 95% of the time.[1] About 180 countries gave the vaccine as part of national programs as of 2006.[13] It is also recommended that all blood be tested for hepatitis B before transfusion, and that condoms be used to prevent infection.[1] During an initial infection, care is based on the symptoms that a person has.[1] In those who develop chronic disease, antiviral medication such as tenofovir or interferon may be useful; however, these drugs are expensive.[1] Liver transplantation is sometimes used for cirrhosis.[1]

About a third of the world population has been infected at one point in their lives.[1] At least 391 million people, or 5% of the world's population, had chronic HBV infection as of 2017.[5] While another 145 million cases of acute HBV infection occurred that year.[5] Over 750,000 people die of hepatitis B each year.[1] About 300,000 of these are due to liver cancer.[14] The disease is most common in the Western Pacific (6.2%) and African (6.1%) regions.[11] In Europe rates are 1.6% and in the Americas they are 0.7%.[1] It was originally known as "serum hepatitis".[15]