The elderly or already suffering from another disease such as the diabetes, asthma or hypertension are the most vulnerable to the epidemic of new coronavirus, which also claims more lives among men than women. The latter represent two thirds of deaths (63.8%).
Since its onset in China in December, Covid-19 respiratory infection has resulted in more than 2,800 deaths out of 83,000 people infected in at least 53 countries. In the majority of cases, it causes mild or moderate symptoms (cough, fever, fatigue …), but in the most severe cases, patients may enter into severe acute respiratory distress or experience acute renal failure, or even a failure of several organs, which can lead to death.
Its average mortality rate remains relatively low – we do not yet know precisely, but it is estimated between 1% and a little more than 3%. It is clearly more than the seasonal flu (around 0.1%), but less than the previous epidemics linked to a coronavirus, much more virulent: 34.5% for the Seas (Middle East respiratory syndrome) and 9.6% for Sras (severe acute respiratory syndrome), the virus of which is close to 80% of the new coronavirus.
Mortality risk goes hand in hand with age
Certain categories of the population are however clearly at higher risk, according to the available data. The most complete analysis to date, published on February 17 by the Chinese authorities then on February 24 in the American medical journal Jama, thus shows that the mortality rate increases markedly with age.
Out of nearly 45,000 confirmed cases, the average death rate is 2.3%. But there are no deaths among children under the age of 10. Up to the age of 39, the mortality rate remains very low, at 0.2%, then drops to 0.4% in those in their forties, 1.3% in those aged 50-59, 3.6% in those aged 60- 69 years and 8% in the 70-79 age group.
People over 80 are most at risk with a death rate of 14.8%. Outside of China, there are also many elderly people among the victims. In Italy, the most affected country in Europe, at least six people among the first 14 deaths were aged 80 or over.
Children are the least affected
The absence of victims among the youngest puzzled specialists, because infants and young children are usually among those vulnerable to infectious diseases.
“This is surprising, because when we look at all the other respiratory infections – bacterial or viral – we almost always have a lot of serious cases in the very elderly, but also in the very young, especially those under the age of five”, underlines Cécile Viboud, epidemiologist at the National Institutes of Health (United States).
“We have to look if there is not a form of cross protection due to the recent epidemic of seasonal coronavirus”, those who cause a simple cold, observes John M. Nicholls, professor of pathology at the University of Hong Kong. A second hypothesis is that the immune system of children is designed “not to overreact in the presence of new infectious agents”.
Tobacco, an aggravating factor
This could be explained “at least in part” by the higher proportion of smokers among men, points Cécile Viboud, tobacco among the parameters that increase the risk of death. Differences in behavior or immune response are also advanced as hypotheses.
Chinese statistics also give indications of other possible risk factors, including having a chronic disease. Mortality rate climbs to 6.3% in patients with respiratory disease (respiratory failure, asthma, chronic obstructive pulmonary disease …)
It is even 10.5% in those who have a cardiovascular disease (heart failure, history of stroke or infarction …) and 7.3% in people with diabetes. Patients with hypertension (6%) or cancer (5.6%) also have a higher mortality rate, while it drops to 0.9% in healthy people.
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