National Respiratory Enteric Virus Surveillance System collaborating laboratories. WHO collaborating laboratories. Sentinel Physicians Influenza Surveillance System. Overall, the 1998-99 influenza vaccine strains were well matched with the circulating virus strains. In temperate regions of the Southern Hemisphere, the influenza season generally peaks during May-August.
Influenza epidemics can occur any time of the year in the tropics.
Therefore, U.S. physicians should continue to include influenza in the differential diagnosis of febrile respiratory illness during the summer, particularly among travelers to the tropics or Southern Hemisphere or among persons traveling with large international groups. However, several laboratories are working to develop a candidate vaccine should the need arise. Strains to be included in the influenza vaccine usually are selected during the preceding January through March because of scheduling requirements for production, quality control, packaging, distribution, and vaccine administration before the onset of the next influenza season. Presented to the 4th International Conference on Emerging Infectious Diseases in the Pacific Rim. Bangkok, Thailand, 1998.