Influenza under close surveillance

A large outbreak of influenza-like illness occurred in Madagascar during July–August 2002. The very sharp increase in the number of cases over a short period of time led health authorities to suspect the appearance of a particularly virulent new influenza virus strain. This triggered immediate international reaction, and a WHO international team assisted local health authorities investigate and control the outbreak. Fortunately preliminary investigation found the virus strain involved was the known A/Panama/2007/99 type, which has been circulating worldwide for several years.