The national coverage grew slightly 1 better i

What will be the virulence and infectiousness of the influenza epidemic which will affect the France next winter What is the level of protection of the vaccine available in pharmacies for a few days Every year at the same time, epidemiologists and virologists are addressing their crystal ball in an attempt to provide the start date, the severity and duration of the next epidemic. A highly speculative exercise, despite the established monitoring networks in place the hexagon and the existence of predictive models quite efficient. "Epidemic this winter should be moderate and affect only about 2.2 million people," said Antoine Flahault, specialist of this disease to Inserm.

The extent and the seriousness of the scourge depend in fact on several factors: the virulence of circulating strain, the climatic conditions to the arrival of the enemy on French soil and the level of vaccination of the population. "But we do not know the real trigger of the epidemic," recognizes Antoine Flahault. In 2003, the virus was very early (6 November), while in 1995 it woke very late (in the middle of March of the following year). The duration of the epidemic is also very variable: four weeks (in 1990) to thirteen weeks (in 1985).

A mutant virus

A dry cold is favourable to the spread of the disease, and experts have two relatively reliable climate indicators: El Niño and La Niña. The magnitude of these two conflicting currents (hot and cold) which originate in the South Pacific provides an index fairly well correlated with the severity of the epidemic. Yet, the past year, forecasters are greatly mistaken. "It is the H1N1 flu strain circulating instead of type H3N2, which was expected," justifies Antoine Flahault. Result, in 2005 - 2006 influenza struck 3.6 million people in France, whereas experts had expected 2.2 million patients. In 1997, misalignment between the strains selected by the who to produce the vaccine and circulating virus was complete (see box). Protection did not exceed 20, and this bad score largely began the image of the country for Pasteur influenza vaccination.

Still posed the threat of the pandemic. "Is still not all of the changes necessary to make the avian virus H5N1 family transmissible between humans", note Sylvie van der Werf, specialist of the respiratory virus at the Institut Pasteur in Paris. We know that this, highly pathogenic strain in animal and human, is circulating since 1997 in Asia. The original virus is, since then differentiated into two major subtypes. One particularly affects the Viet Nam, the Thailand and Cambodia. The other has contaminated a large area (Indonesia, Turkey and China). Genetic diversification has also been detected in humans (244 cases reported resulting in 143 deaths).

These developments confirm the capacity of the virus to mutate according to two different mechanisms. First, slow changes, results of random mutations which add. Then, brutal changes generated by Exchange of genetic material between virus types developed fortuitously in contact blocks. For the moment, who maintains the level of alert of type 3 (of the limited case of person-to-person transmission). According to Bruno Lina, Delegate General of the Group of study and information on flu, "H5N1 is not for this year." Moreover, all the experts are now in agreement on one point: the seasonal flu vaccine offers no residual same protection against a pandemic caused by a virus of the H5 family.

Contraindications to vaccine

All the hype is about avian influenza had finally only a modest impact on vaccination of the French population. The national coverage grew slightly (1 better, i.e. 500,000 people), but it does not exceed 24 of the total population (11 million). The score is naturally best seniors: 68 for those over 65. But 22 of this age has never been vaccinated despite free. Paradoxically, the use of vaccination drops in more than 75 years, which are more vulnerable to infection. "There is only a single contraindications to vaccine". "She is allergic to egg proteins, and these cases are very rare," defends Bruno Lina. "But people forget, and some feel the annual duty as too much hardship," said the expert.

Each year, the winter flu causes close to 6,000 deaths in France.