Laboratory-based influenza surveillance in New Caledonia, 1999-2003.

We aimed to evaluate the annual incidence of influenza in New Caledonia and to identify the circulating viral types and subtypes in order to gather information for the local vaccination programme and regional influenza surveillance. A surveillance network was set up in 1999; it included sentinel practitioners in Noumea and the virology department of the Pasteur Institute. Influenza circulated in New Caledonia every year, regularly during the southern hemisphere winter and occasionally during March-May. Isolates were generally consistent with world surveillance, except in 1999, when a new A/H1N1 variant was identified. This study emphasises the need for regular influenza surveillance, even when performed on a limited scale. Importantly the optimal time for local vaccination was found to be in December or January each year.