[The heat wave of August 2003: what happened?]

A heat wave of exceptional intensity occurred in France in August 2003, 2003 was the warmest of the last 53 years in terms of minimal, maximal and average temperatures, and in terms of duration. In addition, high temperatures and sunshine, causing the emission of pollutants, significantly increased the atmospheric ozone level. Some epidemiological studies were rapidly implemented during the month of August in order to asses the health impact of this heat wave. Excess mortality was estimated at about 14 800 additional deaths. This is equivalent to a total mortality increase of 60% between August 1st and 20th, 2003 (Inserm survey). Almost the whole country was concerned by this excess-mortality, even in locations where the number of very hot days remained low. Excess-mortality clearly increased with the duration of extreme temperatures. These studies also described the features of heat-related deaths. They showed that the death toll was at its highest among seniors and suggested that less autonomous or disabled or mentally ill people were more vulnerable. So, they provided essential information for the setting up of an early warning system in conjunction with emergency departments. The public health impact of the Summer 2003 heat wave in various European countries was also assessed. Different heat waves in term of intensity had occurred at different times in many countries with each time deaths in excess. But, it does seem that France was the most affected country. However, implementation of standardized methods of data collection through all countries is necessary to afford further comparisons. Collaborative studies will be conducted in this way. After theses first descriptive studies, further etiologic studies on risk factors and heat-related deaths were launched and are now in progress. Considering the health impact of the heat wave, national health authorities decided to launch an Heat Wave National Plan including a provisional Heat Watch Warning System (HWWS) for 2004. Developed in collaboration with Metéo France, this HWWS is based upon an analysis of historical daily mortality data and meteorological indicators in 14 French cities in order to define the best indicators and triggers. The public health impact of the heat wave of August 2003 was major. This exceptional event raises questions about anticipating phenomena which are difficult to predict. The collaborative efforts which were developed and the group of actions and studies which were implemented in a context of emergency are now useful for the setting up of early warning strategies and thus efficient prevention.