THE MOLECULAR EPIDEMIOLOGY OF INFLUENZA-VIRUSES

Historical accounts reveal that influenza viruses, which cause a highl y contagious acute respiratory illness in humans, have likely been wit h us for centuries. Epidemics of varying severity occur almost annuall y in temperate climates and are punctuated by the much less frequent b ut more dramatic occurrence of pandemic influenza. Studies of the mole cular epidemiology of influenza viruses have yielded insights that are critical to our current understanding of how novel human influenza vi ruses emerge from the gene pool present among lower animals to cause p andemics of influenza. These studies have also contributed to our unde rstanding of how these viruses, once present in the human population, are able to escape host immune surveillance and thus cause successive infections with related influenza viruses in the same individual.