Influenza

Abstract

Every few years the world faces the risk of a new influenza pandemic. Novel strains of influenza are found in chickens, ducks, or other aquatic birds and result in speculation and occasionally panic that a new influenza epidemic is imminent. These are unique recombinant classes of influenza, an “old” virus that undergoes rapid shifts in its ability to spread from birds or animals to humans, and then from human to human. Influenza changes its antigenicity by two methods: antigenic drift, which is the result of a mutation in a viral gene, usually the hemagglutinin or neuraminidase, and antigenic shift, which results from the reassortment of the eight segments of the influenza genome. More than 50 million people died as a result of the 1918 pandemic, a novel virus infecting humans (H1N1 influenza). The 1918 pandemic flu virus has been reconstructed from samples stored in hospitals and dug up from permafrost. This virus is unique and appears to have been a novel virus not related to swine flu but possibly to an avian source. Other pandemics, such as Asian flu or Hong Kong flu, have followed periodically. The last few years have seen massive culling of poultry due to outbreaks of other recombinant influenza viruses such as H5N1 and H7N9. Vaccines against influenza are rapidly changing by growing the virus in cell culture, and the development of recombinant techniques.