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.
Because of its potential to spread internationally very quickly and the associated mortality and morbidity rates, influenza is among the communicable diseases under closest surveillance in Europe and worldwide. Regional surveillance systems in Europe include various national programmes with the goal to flag up any unusual trends. Several indicators are monitored, such as the weekly rates of consultations for influenza and influenza-like illness cases, coupled with virological data in Germany. In Scotland, predictive models are assessed in order to improve the preparedness to influenza seasonal epidemics.
Back in 1918, countries were far less prepared to predict and respond to influenza epidemics. As an illustration of how extensive and severe an influenza pandemic can be, an article in this Eurosurveillance issue describes the situation in Geneva, Switzerland. The Spanish flu that broke up in the summer 1918 claimed up to 70 million lives around the world, far more lives than the first world war itself from 1914 to 18, until it finally disappeared in 1919.
Such epidemics highlight the need to permanently assess the probability for an influenza pandemic to break up again worldwide and to maintain national and international surveillance programmes.