流行病学 病性肝炎.ppt

* * * 2 Before the discovery of hepatitis A virus (HAV) and hepatitis B virus (HBV) during the 1960s and 1970s, patients with viral hepatitis were classified based on epidemiological studies as having either infectious (transmitted person to person by the fecal-oral route) or serum (transmitted by transfusion of blood products) hepatitis. When diagnostic tests for HAV and HBV infections were developed, HAV was found to be the major cause of infectious hepatitis and HBV was found to be the major cause of serum hepatitis. Hepatitis delta virus (HDV), discovered in 1977, is a defective virus requiring the presence of HBV in order to replicate. However, some patients with typical signs and symptoms of viral hepatitis did not have serologic markers of HAV, HBV, or HDV infection and were categorized based on epidemiological characteristics as having either parenterally transmitted non-A, non-B (NANB) hepatitis or enterically transmitted NANB hepatitis. Subsequently, two additional viruses were discovered: hepatitis C virus (HCV) and hepatitis E virus (HEV). HCV is the major cause of parenterally transmitted NANB and HEV is the major cause of enterically transmitted NANB hepatitis. In addition, some patients with typical signs and symptoms of acute viral hepatitis do not have serologic markers of any of these types of viral hepatitis and can be classified as having non-ABCDE hepatitis. New viruses might be discovered in patients with non-ABCDE hepatitis. * * * * * * The diagnosis of acute HAV infection is confirmed during the acute or early convalescent phase of infection by the presence of IgM antibodies to HAV (IgM anti-HAV). IgM anti-HAV is generally present 5-10 days before the onset of symptoms and is no longer detectable in the vast majority of patients 6 months later. IgG anti-HAV, which also appears early in the course of infection, remains detectable for the lifetime of the individual and confers lifelong protection against infection. Commercial tests are availa