WASHINGTON | The epidemic of the new coronavirus that has appeared in China, called 2019-nCoV, will kill tens of thousands of patients and last for several months at best, epidemiology experts estimate on the basis of the first available data.
“The best scenario would be for it to continue in the spring, for the summer, and then fall off,” said David Fisman, professor at the University of Toronto, and author of a newsletter for AFP. the International Society of Infectious Diseases.
“It’s not going to stop next week or next month,” Alessandro Vespignani, a professor at Northeastern University in the United States, who coordinates a group of researchers publishing real-time analyzes of the epidemic, told AFP. . “You don’t take the risk of saying it’s going to last a long time.”
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Epidemic detectives have no crystal ball and insist that they only have patchy information about the new virus, which appeared in December. They use mathematical models to estimate the number of actual cases, as of today, and compare this epidemic to past epidemics, but many hypotheses remain unclear.
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Until this weekend, it was believed that the infected people were not contagious before the onset of symptoms (fever and breathing difficulties, pneumonia), but the Chinese authorities said on Sunday, having established it, what however, the World Health Organization (WHO) has yet to confirm.
The Americans, on the other hand, said on Monday that they had seen no evidence. If people without fever can infect other people, it will necessarily change the dynamics of the epidemic.
The incubation period is only beginning to be estimated: around two weeks, or even shorter according to the WHO: between two and ten days.
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Patience
Many experts have calculated, in recent days, an important parameter for epidemics: the basic reproduction rate, or “R zero”. It simply represents the number of people infected by an infected person.
Their estimates range from 1.4 to 3.8, according to David Fisman, which is considered moderate.
This number alone is only an average: perhaps some patients have infected many people, and others have infected few. “In itself, no reason to panic,” said Maimuna Majumder of Harvard University and Boston Children’s Hospital to AFP.
She recalls that this rate is 1.3 for seasonal flu (which makes millions of cases per year) and 2 to 5 for SARS (severe acute respiratory syndrome, which caused 8000 cases and 774 deaths in 2002/2003 ). By comparison, for measles, it is 12 to 18.
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With quarantines, isolation measures, routine handwashing, masks … the average number of people infected could drop. If it falls below 1, the epidemic will end.
But the effect of the measures taken by China in recent days will be felt after a week or two, the researchers say, as it is the cycle of the virus.
“It seems more and more that it looks like SARS,” says David Fisman. “SARS was controllable, so we hope it will be too, but we won’t know for a few weeks.”
“It will take weeks, probably months, and no one knows how it will develop,” he adds.
The official number of cases is more than 4,000 in China (more than 100 dead) and fifty outside the country.
The actual number of Chinese cases, including those not detected, according to the international group coordinated at Northeastern, is undoubtedly more than 25,000, says Alessandro Vespignani.
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Researchers at the University of Hong Kong (HKU) estimate that the number currently exceeds 40,000.
“It’s easy to see this figure double or triple, just in the city of Wuhan,” says Professor Vespignani. “If other big cities are affected, the numbers will go up a lot, a lot.”
He does not want to estimate the number of possible deaths. The mortality rate, so far, hovers around 3%, but these rates tend to go up and down: go up at the beginning, when the most vulnerable die, then go down, then go up when others die.
Again, the coming weeks will reveal the real danger of 2019-nCoV.
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