Influenza: vaccination and treatment

Few conditions exert such an enormous toll of absenteeism, suffering, medic al consultations, hospitalization, death and economic loss as influenza. Pa tients at high risk of complications and mortality include the elderly and those with pre-existing cardiopulmonary disease. The outbreak in 1997 in Hong Kong, of avian H5N1 influenza in man, which re sulted in six deaths among 18 hospitalized cases, and the recent isolation of H9N2 viruses from two children in Hong Kong, are reminders that preparat ion must be made for the next pandemic, Since the 1970s, efforts to control influenza have mostly focussed on the split product and surface antigen va ccines. These vaccines are of proven efficacy in healthy adults and are eff ective in elderly people with and without medical conditions putting them a t high risk of complications and death following influenza infection, However, vaccine coverage is patchy and often low, and outbreaks of influen za are not uncommon in well-immunized residents of nursing homes. New vacci nes and methods of vaccine delivery are being del eloped in attempts to ove rcome the limitations of existing vaccines. The antiviral drugs amantadine and rimantadine were developed in the 1960s, but have not been used widely due to their spectrum of activity, rapid eme rgence of resistance, and adverse effects associated with amantadine, The s ite of enzyme activity of the influenza neuraminidase is highly conserved b etween types, subtypes and strains of influenza and has emerged as the targ et of an exciting new class of antiviral agents that are effective both pro phylactically and as therapy.