Influenza

Infections with influenza viruses, especially type A, cause yearly epidemics. The main site of infection is the epithelium of the upper, and to a lesser extent the lower, respiratory tract. It is characterized by acute onset of severe malaise, headache and fever with additional respiratory symptoms. Complications of influenza are frequent in non -immune and immunocompromised patients and associated with increased rates of morbidity, hospitaliziation and mortality. Influenza induces type specific cellular and humoral immune responses. The high rate of genetic mutation of influenza viruses makes further symptomatic infections possible. An inactivated influenza vaccine is available which is effective and safe, and reformulated every year to conform to the circulating virus strains. Individuals over 60 years old, or with an increased risk, should be vaccinated yearly, preferentially in October or November. Antiviral drugs are available which are highly effective in therapy and prophylaxis of infections. Vaccination should be used if possible. Antiviral drugs should be targeted, preferably to patients with a high risk of complications and no protection by vaccines, in order to minimize the development of resistance.