How many people actually die of the flu?
By Journalist Figaro Cécile Thibert Updated 23 / 01 / 2017 to 15: 32 Posted on 17 / 01 / 2017 to 19: 20
Influenza: Why are hospitals energized?
Damien Mascret, a journalist at Figaro Santé, talks about the press conference given by Marisol Touraine on Wednesday morning when France as a whole is affected by an epidemic of influenza.
VIDEOS - Varied figures are circulating, but it is actually impossible to accurately estimate the number of virus victims.
The flu, which appears everywhere at the beginning of the year, may have no more secrets for you. But
for epidemiologists, responsible for establishing the funeral accounts of the victims of the virus, it remains a real headache. "
Each epidemic sees the most extravagant mortality figures that vary from 1 to 15, so much so that even our Minister of Health no longer dares to quote", Says on his blog the general practitioner Jean-Baptiste Blanc. He tries to understand why the media relentlessly repeat the figure of 18.300 additional deaths counted during winter 2014-2015, while the National Public Health Agency France estimates 9000 the number of annual deaths due to influenza identified between 2000 and 2010 and the Center for Epidemiology on Medical Causes of Death
(CépiDc) brandished one of ... 431 flu deaths on average every year!
"In reality, these figures all make sense but they do not correspond to the same thing," says Daniel Lévy-Bruhl, head of respiratory infections and vaccination unit at Public Health France. The 18 300 figure corresponds to the excess mortality observed during winter 2014-2015, mainly related to influenza but also "to other winter factors" (increased cardiovascular risk, presence of other viruses ... ), states the balance sheet of May 2015. That of 9000 dead, him, is an average estimate of the excess excess mortality related to the flu. "These two data are not incompatible. One is an observation in a given year, the other is an average, says Daniel Lévy-Bruhl, co-author of the report of Public Health France from which these figures are derived. The difference of the double can be explained by the fact that there are years without excess mortality, as was the case in 2016. "
And then there are the 431 deaths recorded by CépiDc, a laboratory of Inserm responsible for drawing up each year the statistics of medical causes of death.
To obtain this figure, researchers count death certificates completed by doctors mentioning influenza as the cause of death. How then to explain that, on the 9 000 additional annual deaths related to influenza estimated by Public Health France, only 431, ie 5%, have been identified as such by CépiDc?
Death indirectly related to the virus
«
Influenza is hardly ever the immediate cause of death. Very often, doctors do not even know that the deceased was carrying the virus, which is why it is not written on the certificate ", explains Pierre-Yves Boëlle, biostatistician and professor in epidemiology at Pierre University and Marie-Curie (Paris). "In the elderly affected by influenza, the majority of deaths occur late compared to influenza infection, either because bacteria take advantage of the weakness of the patient to over-infect, or as a result of decompensations related to precarious general state. In this case, the flu is often not mentioned on the death certificate, "adds Daniel Lévy-Bruhl. This careful accounting can only result in a gross underestimation of the mortality due to influenza.
Conversely, the figure of
18 300 is the result of an overestimation. How was it calculated? "In the absence of an epidemic, the mortality curve follows a periodic movement, which includes a winter peak. Based on this model, all additional deaths that occur during an influenza epidemic are attributed to influenza, explains Boëlle. Certainly, there are methodological biases and significant differences between the data. But this is the best statistical estimate that we currently have. "An approach that has been adopted by all European countries.
The epidemiological fog surrounding the number of deaths attributable to the virus
also asks the number of deaths averted by the vaccine, estimated at 2 500 per year, by Santé Publique France. "
We do not have good evidence today that vaccination reduces mortality in the elderly, however it avoids infections, so
beforehand deaths, "emphasizes Professor Boëlle.
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"We make science with facts, like making a house with stones: but an accumulation of facts is no more a science than a pile of stones is a house" Henri Poincaré