The SARS-CoV-2 virus and the disease it causes, Covid-19, have not revealed all their secrets. Five key questions remain unanswered for the moment.
1. Why is Covid-19 benign for some and very serious for others?
How is it that Covid-19 produces no or few symptoms in 80% of cases (according to the WHO) while, in some patients, it induces a high fever, and even pneumonia which can be fatal?
During the peak of the epidemic in China, Leo Poon, of the medical school of Hong Kong, compared, with a Chinese team of the University of Nanchang, people weakly reached with severe patients. The results were published in the British medical journal The Lancet. We learn there, details the site 20 minutes, that severely affected people are “significantly older” and that the concentration of virus in their samples is “about 60 times higher” than in those weakly affected.
Is it due to a poorer age-related immune response, or is it the result of exposure to higher doses of virus during contamination? Work on a different virus, measles, has shown that the severity of the disease is correlated with the dose of initial exposure to the virus. It is unclear whether the same is true for the Covid-19.
2. Does the virus stay in the air?
The coronavirus is transmitted by physical contact and respiratory tract, in particular the droplets of saliva expelled when one coughs. But can it remain suspended in the air like the seasonal flu? Mystery.
An American study published in the New England Journal of Medicine (NEJM) shows that the new coronavirus can survive in the laboratory for three hours in the form of particles in the air. We can therefore find virus in the air but we do not know if it is infectious.
3. Why are the children spared?
Children are much less prone to Covid-19 than adults. And if they develop symptoms, they are usually mild. RTL reports that a Chinese study published in the journal Nature shows that, out of ten children studied, affected by Covid-19, none developed a severe form, their symptoms being limited to sore throat, cough and mild fever. According to this research, children living with sick people are two to three times less likely to get the virus than adults. Why? We do not know.
The same characteristic was noted for the SARS virus in 2002-2003.
4. How many people are infected?
How many people have already caught the virus? Aside from the few countries that have implemented aggressive screening policies, such as South Korea and Germany, knowledge of the number of infected people is very approximate.
Having a clear idea of the extent of the epidemic is nevertheless crucial to isolate the carriers of the virus and better treat them. And, in a second step, it will be precious to know who has already caught the virus and is a priori already immune. This will only be possible with the arrival of a new generation of tests, called serological tests, which will target the detection in the blood of the immune signature left against SARS-CoV-2.
5. Is this coronavirus sensitive to the weather?
Will the pandemic fade with the arrival of sunny days in the northern hemisphere? Very clever who can answer this question.
According to Paris Match, a study by Hong Kong academics has shown that the SARS virus, which struck Asia in 2002-2003 and which is a close cousin of the current coronavirus, resists better in low temperatures and low humidity.
However, a recent American study, from Havard Medical School, points out that “the only weather changes will not necessarily lead to the decline of Covid-19 cases without the implementation of major health interventions”.
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