Microbiology
Summary
Hepatitis B virus (HBV), a member of the Hepadnaviridae family, is an enveloped DNA virus with a unique genome that is partially double-stranded and partially single-stranded. HBV's key surface glycoprotein is its surface antigen (HBsAg), while its core protein forms its nucleocapsid. Its E antigen is a secretory protein processed from the precore protein and signifies active replication. Transmission of HBV can occur sexually, through contaminated needles, or vertically from mother to child during pregnancy.
Symptoms of acute infection include fever, rash, joint pain, RUQ pain, jaundice, and anorexia, while chronic infection may lead to liver cirrhosis. The risk of infection progressing to chronic hepatitis B is age-dependent: approximately 90% in infants, 50% in children, and 2-5% in adults. HBV-associated complications include membranous nephropathy, membranoproliferative glomerulonephritis, and systemic vasculitis polyarteritis nodosa. Diagnosing HBV often relies on serological markers, with the serological window being negative for both HBsAg and anti-HBs antibody, and vaccination status indicated by a negative HBsAg and a positive anti-HBs antibody. Treatment options include the nucleoside reverse transcriptase inhibitors tenofovir and entecavir, and prevention is facilitated by the recombinant hepatitis B vaccine, recommended for all newborns and high-risk adults. Furthermore, hepatitis delta virus, a satellite virus to HBV with a negative-sense RNA genome, can cause coinfection or superinfection, with the latter leading to severe hepatitis and a higher risk of chronic infection.
Lesson Outline
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FAQs
The hepatitis B virus (HBV) is part of the family Hepadnaviridae and the genus Orthohepadnavirus. It is a DNA virus that specifically infects the liver and can result in both acute and chronic diseases.
Hepatitis B infection is diagnosed primarily through blood tests that detect specific serological markers. These tests measure the presence or absence of the hepatitis B surface antigen (HBsAg), antibodies against the hepatitis B virus (anti-HBs and anti-HBc), and the hepatitis B e antigen (HBeAg). A positive HBsAg indicates an active infection, while the presence of antibodies (anti-HBs) can suggest past exposure or successful vaccination. Further tests, like liver function tests and DNA viral load, can help determine the severity and stage of the disease.
Chronic hepatitis B can lead to a range of complications including cirrhosis, liver failure, or liver cancer. It can also induce conditions such as membranous glomerulonephritis and polyarteritis nodosa, with the latter being a type of vasculitis. Chronic HBV infection can be fatal if not properly managed.
Treatment for Hepatitis B involves antiviral medications to slow the progression of the disease and prevent liver damage. The exact treatment depends on the stage of the disease, the presence of any complications, and the patient's overall health. Patients should discuss their treatment options with their healthcare provider.
A co-infection occurs when both HBV and hepatitis delta virus (HDV) are contracted simultaneously. This typically leads to an acute, transient infection, which may or may not progress to a chronic state. A superinfection happens when an individual already infected with HBV later contracts HDV. This scenario often results in an acute, more severe form of hepatitis and carries a higher risk of progressing to chronic infection.
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