Managed Care - October 2008 - (Page IS2) FACULTY PRESENTATION An Introduction to Influenza: Lessons From the Past in Epidemiology, Prevention, and Treatment ROBERT B. BELSHE, MD St. Louis University, St. Louis velope composed primarily of the antigenic surface protein hemagglutinin (approximately 70 percent) and the enzyme neuraminidase (approximately 30 percent). Less Better understanding of viral biology and than 1 percent consists of the M2 ion channel. Inside the the origins of influenza epidemics and panenvelope is an antigenic matrix protein lining. The virus demics may improve diagnosis and disease genome exists within this structure and comprises eight control. Advances to stop the spread of dispieces of single-stranded RNA formed into a ribonucleoprotein helix. The hemagglutinin on the surface proease, including live-attenuated and invides the site of attachment for the virus to the host cell. activated vaccines and new antiviral agents, The neuraminidase is responsible for facilitating the repromise to reduce disease burden, mortallease of new virus from host cells and, together with the ity, and morbidity. M2 ion channel protein, is a major target for drug intervention. Mutations in the antigenic components are preInfluenza is a prevalent disease with a large burden of dominantly responsible for the development of virus morbidity and mortality (Couch 1986, Sullivan subtypes and alternative strains. 1993, Simonson 1997). With annual outbreaks There are two major types of human inof epidemic or pandemic proportions and a fluenza virus — influenza A and influenza B. (A relatively high death toll among vaccine-prethird type, influenza C, does not cause much ventable diseases, control of influenza has beillness and is not addressed here.) Influenza A, come a major public health goal. Over the last a form that can be found in certain animal 30 years, understanding of the molecular biolspecies and humans, is responsible for most ogy of the virus and the pathophysiology, natcases of seasonal flu, especially broad-reaching ural history, and treatment of the illness has adepidemics and pandemics. Influenza A is subvanced enormously, yet there has not been ject to frequent antigenic drift, or changes in its much progress in reducing death from inantigenic profile due to point mutations in the ROBERT B. fluenza. Advances in disease control, including gene encoding hemagglutinin that occur durBELSHE, MD the availability of new antiviral agents and both ing viral replication. Influenza B is a more stainactivated and live-attenuated vaccines, as well as imble virion found primarily in humans, and is identified proved understanding of how the disease spreads, hold most often as the cause of local outbreaks. Because of gepromise that effective control of influenza might reduce netic similarities in human and animal forms of inits medical and economic impact within our lifetimes. fluenza A, it is possible for RNA from animal viruses to exchange segments with the human influenza virus The influenza virus genome. It has been shown that this type of “reassortment” event, in which the genetic material from animal Studies of the molecular biology of the influenza virus virus is integrated into the genome of a related human have revealed important insights into the genetics of intype A strain during co-infection, can produce a new viral fluenza and how its evolution affects human infection strain of high virulence (Mumford 2007, Jin 2005). during influenza epidemics and pandemics. Influenza Whereas the body develops immunity upon exposure to virus is a spherical or ovoid body with a lipid bilayer enone influenza virus strain and its antigenic relatives, new cross-species antigenic variants may not be recognized by Robert B. Belshe, MD, is professor of medicine at St. Louis the immune system, therefore causing widespread and University. SUMMARY 2 MANAGED CARE / SUPPLEMENT
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.