HEALTH – Almost two months after the emergence of the new coronavirus, the world is preparing for a possible pandemic. As the number of people infected in China continues to decline, international cases are increasing day by day.
In order to best prepare for an epidemic risk and react in the best possible way, scientists from all over the world are launched in a race against the clock aiming to better understand this new coronavirus, Sars-Cov2, and the disease it causes, covid-19.
We obviously know more and more, even if the gray areas are still substantial. The virus seems very contagious and its mortality, if it is full of uncertainty, seems much lower than that of Sars in 2003, but much higher than that of a simple flu. It could be around 1%, although that figure could move a lot, one way or the other. What take Sars-Cov2 seriously and do everything to fight it. But for that, you have to know it.
Among the uncertainties that remain, certain cases (or their absence) particularly intrigue scientists.
“Asymptomatic” cases, or the quest for transmission
One of the biggest unknowns today, aside from the real death rate, is certainly the true extent of the contagion. Because if the WHO communicates the number of people infected every day, we only see the tip of the iceberg.
The most severe cases are normally almost all taken into account. On the other hand, it is impossible to know whether the mild cases, or even those without symptoms, are all listed. For the latter, we speak of “asymptomatic” cases, without specifying whether they could end up having symptoms or not.
Except that it is very difficult to verify this: people without symptoms are unlikely to report to the health authorities. Precisely, elements allowing to see more clearly begin to emerge from the Princess Diamond, the cruise ship on which an epidemic of coronavirus took place off Japan. By analyzing in detail the data from these approximately 3000 passengers, researchers estimate, in a study which still needs to be validated, that 34.6% of the cases would be asymptomatic.
But even if we can figure out how many people have little or no symptoms, and for how long, a second unknown remains. The question is whether these individuals can transmit the coronavirus. And in what proportions. Here, the data is still limited. But two recent studies claim to have studied clinical cases of symptomless patients who could have contaminated relatives. Too partial data to draw conclusions for the moment.
The risk of reinfection
In Japan, a woman was diagnosed as a carrier of the coronavirus a second time, the government announced on Thursday 27 February. Tested in late January, she was discharged from hospital on February 1. Similar cases have reportedly taken place in China.
According to microbiology professor Florian Krammer, these people were not re-infected. On Twitter, he remember that the other known coronaviruses cause an immune response and the creation of antibodies that last between one and three years. Covid-19 appears to elicit a similar response. “Reinfection, especially in the short term, is therefore extremely unlikely,” he says.
The most plausible explanation, he said, was that the person was still infected with the virus, but the test was negative. Sort of a diagnostic error. It remains to be seen whether these people are still contagious.
Can animals be infected?
Friday, February 28, Hong Kong announced that a sick woman’s dog has been tested for coronavirus position. But that sounds rather strange, because so far, no tangible evidence of contamination from domestic animals has been established.
Hong Kong authorities said that if traces of the virus were found in nasal and oral samples, the animal showed no symptoms. Tests are currently underway to check if the animal is indeed carrying the virus or if it is a contamination coming from the outside.
When in doubt, Hong Kong invited the sick to quarantine with their pets.
The mysterious absence of children
One of the main mysteries surrounding the new coronavirus strangely concerns the absence of a case. Indeed, children are underrepresented among the sick. The most comprehensive study, which analyzed 44,000 infected Chinese, found only 416 children under the age of 10 and 549 adolescents aged 10 to 19. No deaths below 10 years have been recorded.
Good news, of course, when you know that certain diseases affect young people in particular. But that raises questions. It remains to be seen whether children are really unlikely to catch covid-19, or whether their symptoms are simply very mild, and therefore hardly detectable. In this case, the children could be undetectable providers of the disease.
Knowing which of these two scenarios is the right one will allow health officials to better judge the usefulness of closing schools to prevent the spread of the coronavirus.
See also on The HuffPost: Coronavirus has brought Chinese air traffic back for years
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