Influenza.

Influenza is an acute respiratory illness of global importance that causes considerable morbidity and mortality every year. At the beginning of the millennium, influenza will still be an emergent or re-emergent infection because of the viral ability to mutate. Global influenza surveillance indicates that influenza viruses may vary within a country and between countries and continents during an influenza season. Virologic surveillance is of critical importance in monitoring antigenic shift and drift. Disease surveillance is important in assessing the impact of the epidemics. Both types of information provide the basis of vaccine composition and the correct use of antivirals. Laboratory diagnosis is of critical importance for the global surveillance of influenza and may allow the timely use of antiviral drugs. Viral isolation remains the gold standard for laboratory diagnosis; however, several new rapid diagnostic tests are available or in development. The clinical spectrum of the disease varies from asymptomatic infection to the classic flu syndrome, and respiratory and nonrespiratory complications are observed particularly in high-risk groups. Current inactivated influenza vaccines have shown efficacy and effectiveness in preventing influenzalike illness, hospitalization for pneumonia, and death and in reducing health care costs. Because of the annual administration of the vaccine and the short period of time where it can be administered, strategies directed at improving vaccine coverage are of critical importance. In this sense, experiences obtained in different countries, such as with the National Immunization Campaigns developed in Argentina, provide one model of massive vaccine administration. In addition to current vaccines, new live attenuated vaccines will permit a most effective prevention of influenza in the community in the near future. A new type of antiviral, neuraminidase inhibitors, offers valuable benefits in the prevention and treatment of influenza A and B. A future pandemic of influenza seems inevitable. There is wide recognition that preparation for the next pandemic requires that infrastructure be in place during interpandemic periods for implementing preventive and therapeutic measures. The WHO has established a pandemic influenza task force, and a number of countries in Latin America have developed formal pandemic plans. These national and international efforts are essential to reduce the mortality and morbidity in the next influenza pandemic.