The coronavirus epidemic originating in Wuhan risks becoming a pandemic, warned WHO director Tedros Adhanom Ghebreyesus on Monday. According to him, the “window of opportunity” to stem the spread of the virus is closing. Explanations.
“The window of opportunity closes.” This is the warning issued by Tedros Adhanom Ghebreyesus, head of the World Health Organization, Friday 22 February, to the international community concerning the epidemic of coronavirus, the focus of which is located in Wuhan, in the center of China.
An alarmist statement especially since it was made before the new cases of infection recorded in Italy and Iran, this weekend. This spread of the epidemic of Covid-19, which has already infected 77,000 people and caused the deaths of nearly 2,600 worldwide, is of increasing concern.
Australian researcher Paul Hunter, one of the most eminent specialists in the new coronavirus, said that “the past 24 hours have brought us very close to the point of no return.”
Law of Large Numbers
These warnings relate to when the transmission of the virus can no longer be contained. “At the start of an epidemic, there is a zero patient who will infect a random number of people. We then calculate this random variable – called R0 – based on what we know.
This is the average of individuals infected with a carrier of the virus. If this number is less than 1, the epidemic will quickly go away on its own. When this initial variable is greater than 1 [it is 2.5 for covid-19, note], there is a risk that the epidemic will take off ”, explains Jean-Stephane Dhersin, deputy scientific director of the National Institute of mathematical sciences and specialist in epidemic modeling, contacted by France 24.
There is then a period of time during which it is possible to contain the spread of the disease by deploying the necessary means. This “shooting window” depends, mathematically, on the number of people infected.
“The more people affected, the more we can know with certainty the number of people they will in turn contaminate. The virus then behaves exponentially and the epidemic explodes. This is the mathematical law of large numbers, ”explains Jean-Stephane Dhersin.
In other words:“ We can only act at the start of an epidemic by trying to reduce the average number of people infected with a virus carrier, by establishing measures like quarantining or pushing people to put on masks [for viruses that, like the coronavirus, are transmitted through the respiratory system, editor’s note]. After, it’s too late ”, notes this mathematician. Italy and Iran constitute a “turning point of the epidemic” The moment when this rocker is likely to intervene in the case of Covid-19 remains a big unknown.
Admittedly, the virus did not appear until a little less than two months ago and we can still estimate to be at the beginning of the epidemic. But with nearly 80,000 infected, it has already done considerable damage.
For a researcher based in China, who preferred to remain anonymous, “if the point of no return is not yet reached, it is only a matter of days before this milestone is crossed.”
“We are at a turning point in the epidemic and the way the situation will be managed in Italy and Iran is critical for the future,” said Frederic Tangy, director of the vaccine innovation laboratory at the Pasteur Institute, contacted by France 24. For this specialist, WHO is right to say that there is still time.
The overwhelming majority of the cases are in China, “and we really have to thank Beijing for the measures taken” to slow the spread worldwide. He adds that “if we follow the Chinese curve, we are currently at the peak of the peak and the increase in cases slows down”. Remains the situation internationally where “each new outbreak of infection can be seen as the beginning of a new epidemic, and the pandemic will not really be declared until health services are overwhelmed by the number of foci of infection in the world ”, specifies Frederic Tangy.
He believes that the list of states confronted with coronavirus s still stretches from three or four countries as badly affected as South Korea or Iran before reaching the point of no return. Hence the importance of Italy, which risks becoming the gateway to the virus in Europe. Carriers without symptoms All the experts interviewed agree that the best bulwark against the spread of Covid-19 is hospital staff. “They are the ones who currently protect the outside world,” says Frederic Tangy.
But the pathogen also has a weapon that distinguishes it from other coronaviruses, such as SARS (Severe Acute Respiratory Syndrome) and the Seas (Middle Coronavirus). East) and makes fighting spread more difficult. “There are more cases of carriers of the virus who have no symptoms but can still transmit the virus, which makes screening more difficult,” said Jean-Stephane Dhersin.
This may explain, according to the experts interviewed, the absence of cases recorded in areas of the globe which nevertheless have strong commercial or tourist links with China. “I find it very astonishing, for example, that there is absolutely no case of coronavirus in Latin America or Eastern Europe, two regions yet economically very linked to China,” notes Frederic Tangy.
And despite the efforts of the international community, the epidemic came to cross the point of no return? “It will then be exactly like an influenza epidemic, there is nothing we can do except wait for it to pass”, concludes Jean-Stephane Dhersin. Concretely, Frederic Tangy expects that, in this scenario, “the measures are taken in Italy or China, that is to say essentially quarantines, will occur everywhere”.
