Why coronavirus mortality rates are so different from country to country

Rise of racism, supermarkets stormed, whole neighborhoods deserted, analogies with the plague… The whole world is giving in to panic as the death toll from the new coronavirus continues to rise. And the general anxiety is probably due to the blurring of the virus, particularly in terms of its mortality rate. According to Tedros Adhanom Ghebreyesus, Director-General of WHO, 3.4% of the world’s infected people have died. That’s more than three times the case law rate for seasonal influenza (less than 1%). And while it makes sense for the ratio to change with the age of the sick, it is surprising that it varies by country.

In its 8 March report on the epidemic, WHO reported 105,586 confirmed cases, spread across 101 states, for 3,584 deaths. And from one country to another, the mortality rate can change drastically. Switzerland, for example, has a lethality of 0.76%, compared with 5.16% for the United States… That’s a lethality almost 7 times higher. In France, with 10 deaths for 706 cases confirmed on Sunday (March 8th), the mortality rate of the virus is estimated to be 1.42%, according to the WHO. Fluctuations that challenge, and even fuel, false information and conspiracy theories that states lie about the true lethality of the virus. Assumptions, however, would justify these large variations. Here are some factors that can cause these fluctuations from one territory to another.

Problematic data collection
These variations in mortality rates are primarily due to the reliability of the data. Especially at the beginning of the epidemic, when it is almost impossible to establish a complete count of the number of patients. Indeed, the disease caused by Covid-19 can be asymptomatic. Many people do not go to see and are never counted. In any epidemic, there is a tendency to overestimate the caseity rate at first, and then, as infected people are more widely detected and management of severe forms improves, the rate decreases. During the Ebola epidemic in West Africa, we started from a case 1 rate of 70%; it then went down to 40%,” Professor Jean-François Delfraissy told Le Monde. Temporality therefore also has its importance in calculating the case law rate. It is likely to drop as mild cases are counted

Variations between countries can also be explained by the various measures taken to screen for Covid-19. South Korea, for example, conducted a massive screening campaign, finding infected people who were, in fact, barely ill. As a result, the mortality rate dropped significantly, as the number of mild cases was recorded. WHO therefore takes tweezers in its daily report on the epidemic and distinguishes the data according to the census method. Jean-Stéphane Dhersin, deputy scientific director of the CNRS National Institute of Mathematical Sciences and Their Interactions, explains: “Data collection is a big problem. The criteria for counting patients is not uniform across the world. In some countries, it is enough to have a fever and another symptom to be considered sick.

Unequally effective health systems
In the fight against coronavirus, the effectiveness of health systems and the quality of hospital infrastructure would be crucial. “The key challenge is to prepare the health system to deal with a lasting epidemic, to take measures to prevent a sudden influx of large numbers of serious or serious cases that could overwhelm the capacity for care,” explains Professor Delfraissy, interviewed by Le Monde.

This is probably why Switzerland, which ranks third in the Legatum Institute for State Health Systems, has such a low mortality rate (0.76%). Like Singapore — 1st in the ranking, 0 deaths for 138 confirmed cases — or Japan — 2nd in the ranking, 6 deaths for 455 cases recorded. The United States, which has the highest case case rate (5.16%) 59th place in the ranking of health systems…

However, the performance of its health system has not preserved Italy, which has a significant mortality rate (3.98 per cent). despite an honourable place (17th) in the Legatum Institute rankings. Indeed, even a high-performing health system can be overwhelmed by the epidemic. Professor Charles-Hugo Marquette, head of the pneumology department at the Nice University Hospital, told Le Monde: “Hospitals are calibrated for a certain level of activity. In the event of a massive and sudden influx of patients in acute respiratory distress, even if the teams are competent and have the necessary equipment, they can quickly be caught off guard. Especially if infections are multiplying in caregivers, as we see in Lombardy at the moment.” And for Italy, the second-oldest country in the world, demographics could also play a role in the mortality rate.

The median age of populations
The mortality rate of coronavirus increases significantly with age. This could be a determining factor in the case rate of caseity in a given territory. The Italian population, for example, is relatively old. With a median age of 45.1 years — the highest in Europe — according to the CIA World Factbook, Italy has a mortality rate of 3.98% for 5,883 reported patients. In Iran, which records almost the same number of cases (5,823), the median age is lower (29.1 years) and the mortality rate is also lower (2.49%).

These demographics therefore seem to have a real impact on the mortality rate: Iran is only 88th in the Legatum Institute of Health Systems ranking, while Italy ranks 17th… However, in the case of Japan, it seems that it was the health system that was the determining factor. The country, second in the Legtatum Institute’s ranking, has a case injury rate of only 1.32%, despite a relatively elderly population (median age of 46.9 years).

Two strains of coronavirus?
A final explanation for these fluctuations is sometimes advanced: Chinese researchers have identified two different strains of the virus. The older strain is said to be less contagious and less deadly than the strain ,”L,” futura Science reports. These two strains could have spread unevenly across the territories, and this could be one of the reasons for these fluctuations. However, this study has never been confirmed and it is unlikely to have a real impact on the variation in mortality rates by country.

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