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Influenza Virus Influenza or “flu” is caused by a RNA virus that belongs to orthomyxovirus group (Schaechter, et al, 1999). It is an enveloped virus that is single stranded, has helical RNA and it’s envelop is made up of a lipid bilayer as well as proteins and external glycoproteins (Schaechter, et al, 1999). Numerous vaccines have been developed every year, however it can not be stamped out due to the viruses ability to change it’s main antigens hemagglutinin and neuraminidase (Schaechter, et al, 1999). This prevents a person from developing immunity to new strains of influenza that arise. Immunity to influenza strains or any other virus has a very simple system. Once the body has had initial contact with the virus eventually it will make enough specific antibodies to destroy the virus. Some of these antibodies then remain circulating in the body forever. If the body then comes in contact with the same virus it should immediately kill off the virus. However this process does not seem to work with influenza. Influenza exists in three types: Influenza A, B, C. Influenza type A has been studied extensively, in fact the complete amino acid sequence is known (angelfire, 9/10/02). The influenza A virus is a glob