HEALTH – More fear than harm. The twenty French returnees from China who presented with “symptoms” did not finally contact the new 2019-nCov coronavirus, the Ministry of Health announced on Monday (February 3rd).
Passengers suspected of having contacted this new virus, which must have emerged through infections with infected animals in a market in Wuhan, had “rather colds”. Two tests on the first repatriation had also turned out to be negative a few days earlier.
Logic: the effects of this coronavirus, apart from the serious complications which led to the death of at least 362 people, are very classic. So there is a huge chance, with equal symptoms, of having a very common disease. This is why it is necessary to carry out a special test to detect the 2019-nCov virus. What complicate the task of health institutions, which do not question elsewhere on … the absence of symptoms.
(Too) common symptoms
“The main symptoms are fever as well as other respiratory manifestations, such as a cough,” explains the HuffPost Olivier Terrier, CNRS and Inserm researcher at the International Center for Research in Infectious Disease.
Problem: “These symptoms are similar to those that are generally observed for influenza or other respiratory infections, there are no symptoms known to be specific to an infection by the coronavirus 2019-nCov”, specifies t -he.
A study published in the Lancet January 30th examined in detail the state of health of 99 Chinese among those first affected by the coronavirus. It is the most comprehensive analysis published in a scientific journal at present, but it certainly focuses on the most serious cases, requiring hospitalization.
The result is more in line with what is expected: 83% of patients had a fever and 82% were coughing. 31% had difficulty breathing, and about one in ten reported muscle pain, confusion or headaches.
“Cases of respiratory distress and kidney failure have been described in the most serious cases, these are symptoms that are also encountered in severe forms of other infections,” said Olivier Terrier.
Double-edged “soft” cases
If the serious cases are rather listed, the great uncertainty concerns precisely the patients for whom the coronavirus 2019-nCov has a less strong effect. “The data indicate that there are many milder forms of the infection, with lesser symptoms,” said Olivier Terrier.
All of this is still in its infancy and it will take a few days or weeks for more information. But if this is confirmed, there are two consequences. The first is positive: the temporary mortality rate, which is regularly communicated, between 3% and 2%, could drop drastically.
Because when you say mild cases you don’t go to the hospital or the doctor. And therefore undetected cases. So in a study published on January 31 in Lancet, researchers estimate that 75,815 people were infected by the coronavirus on January 25. At that date, the WHO had confirmed 41 deaths for 1320 cases, that is a mortality rate of 3.1%. But if there were finally 75,815 infected, the death rate would be 0.05%.
Be careful not to declare victory too quickly: if the number of cases is underestimated, the number of deaths could be too. In general, it is very difficult to estimate the death rate from an infectious disease.
There is obviously a downside to the medal. If people are affected by the virus but are not very sick, they are more likely to spread the coronavirus.
Questioned by statMike Ryan, director of the WHO emergency health program, said that “a relatively mild virus can do more damage because more people could catch it.”
The asymptomatic risk
Example: if the SARS epidemic was brought to a halt relatively quickly, despite a delay in switching on the Chinese government, it is precisely because the patients were visible and well supervised, because they all had fairly significant symptoms. “The detection and isolation of such cases [peu symptomatiques, NDLR] will be a major challenge, ”they say.
In an analysis, researchers from Imperial College London recall that these cases of infectious people, but with mild symptoms, did not really exist during the epidemic of the coronavirus Sras, which also came from China in 2003.
And there is another possibility that raises fears that the quarantine and border control measures will not be effective: some patients could be contagious while being completely asymptomatic.
So the New England Journal of Medicine published a study on January 30 suggesting transmission of the 2019-nCov coronavirus after asymptomatic contact. In short: a Chinese woman came to Germany and participated in a meeting with a German when she showed no symptoms. Once on the plane only, she felt sick. A few days later, the German with whom she had a meeting tested positive for the new coronavirus, as did two people who had never seen the Chinese woman.
Little or no symptoms, that is the question
However, we should not once again draw hasty conclusions. Infectious Disease Researcher Isaac Bogoch asks himself on Twitter how asymptomatic the Chinese woman was. If the symptoms are sometimes close to a cold, perhaps she has not notified it?
Mike Ryan also explains that WHO data suggests that people who are classified as asymptomatic actually had symptoms, but may be weaker.
In all cases, there is a good chance that even if these asymptomatic contaminations exist, they are very weak. If nothing is yet certain with 2019-nCov, “the scientific literature shows that there is a correlation between the importance of the symptoms and transmission of the influenza virus, responsible for the flu,” recalls Olivier Terrier.
So far, what we do know is that “the main vector of coronavirus infection is people with symptoms,” says Mike Ryan.
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