[Influenza: from vaccine prevention to antiviral therapy]

Influenza is a highly infectious disease responsible for dangerous epidemics, especially in patients at high risk. The vaccine exerts a valuable protective effect estimated up to 70% and is still considered as the key-approach against influenza. Antiviral agents of the first generation (amantadine, rimantadine, ribavirine) have limited use because of poor tolerance and occurrence of resistance. Zanamivir or Relenza, marketed by Glaxo Wellcome, is a new virostatic drug acting as a neuraminidase inhibitor. It prevents the release of new viruses and so stop the propagation of the infection. It must be taken orally by inhalation within 48 hours after the onset of symptoms. The treatment lasts 5 days (10 mg twice daily). Its efficacy has been demonstrated in controlled clinical trials, and its tolerance is generally excellent. However, caution is recommended in patients with asthma and chronic bronchitis because of the potential risk of bronchoconstriction. No resistance has been detected until now. Zanamivir is active on all strains of influenza A and B viruses.