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Paris (AFP)
The patient entered the Washoe County Community Testing Station in the US state of Nevada on April 18 with a sore throat, dry cough and headache, but there was no reason to be concerned.
She was only 25 years old, had no prior medical conditions, and although the PCR nasal smear test for Covid-19 she took came back positive, she soon felt good again.
Thirty-five days later, he was rushed to the emergency room, with shortness of breath and a severe fever, and given oxygen.
It had become the first confirmed case of Covid-19 reinfection in the United States.
So far, there have only been a handful of similar cases around the world, and experts say it is too early to draw radical conclusions from such a small count.
But the possibility of being infected with Covid-19 again, and getting even sicker the second time around, could have a significant impact on how governments chart their way out of the pandemic.
In particular, reinfections can make the idea of herd immunity – that is, a high enough percentage of people who eventually become immune to Covid-19 – unrealistic.
“Cases of reinfection mean that in some people, the immune response is not sufficient to protect them from infection or disease,” Akiko Iwasaka, professor of Immunobiology and Molecular, Cellular and Developmental Biology at Yale University, told AFP.
“Reinfections by SARS-CoV-2 (the virus that causes Covid-19) mean that the immunity acquired through a natural infection is not perfect.”
Researchers documenting the Nevada patient’s case offered a number of possible explanations for how he may have gotten sick twice.
You may have been exposed to a very high dose of the virus the second time, causing a more acute reaction.
Alternatively, it may have been a more virulent strain of the virus.
The study, published this week in The Lancet Infectious Diseases, listed other confirmed reinfections in Belgium, the Netherlands, Hong Kong and Ecuador.
– Too early to tell? –
Frederic Altare, director of Immunology at the Inserm Research Center for Oncology and Immunology in Nantes-Angers, said there is currently little evidence that Covid-19 reinfection is going to be a “major problem” given the low case numbers.
“With the number of people who have been infected, there are only a dozen confirmed reinfections, that’s not a lot,” he told AFP.
But others said it was difficult to accurately measure reinfection numbers given the relative lack of testing during the first wave this spring.
In other words, many people, in theory, could have been infected in March or April and remain asymptomatic, only to test positive later in the year when they were reinfected, but this time with symptoms.
According to Jeffrey Shaman, Professor of Environmental Health Sciences at Columbia University’s Mailman School of Public Health, the main obstacle to determining reinfection numbers is that SARS-CoV-2, unlike other coronaviruses that circulate among humans, it is completely new, epidemiologically. Talking.
“The world has only been dealing with this for several months,” he told AFP.
“We don’t know if (reinfection) will be common or as likely to be as severe as the initial infection.
“It is really important to understand what this virus is ultimately going to do and how difficult it will be to make a universal vaccine,” Shaman said.
– Other viruses –
While it’s difficult to say for sure how widespread or frequent Covid-19 reinfections will end up, scientists can look for clues in similar viruses.
Lia van der Hoek, a coronavirus expert at Amsterdam UMC, has studied pathogens for decades.
She was the lead author of a paper published last month in Nature Medicine that investigated the other four coronaviruses that humans can contract.
The study recorded 10 healthy individuals for more than 30 years and found that the patients were infected multiple times with the virus.
One patient became infected on 17 separate occasions during the study period.
“Covid-19 will probably behave the same,” he told AFP.
Shaman also studied the circulation of other coronaviruses, followed 12 healthy individuals and showed that they could be reinfected a second time.
He said that evidence from other respiratory viruses suggests that widespread Covid-19 reinfections are by no means impossible.
– ‘Dangerous’ herd immunity –
On Monday, researchers in the Netherlands published the case study of an 89-year-old woman who died after contracting Covid-19 twice.
She had been treated for cancer and her immune system was damaged as a result, making her more susceptible to serious infections.
As the world searches for a vaccine, Iwasaka said that any eventually safe and universal inoculation would need to generate higher levels and longer-lasting immunity in people than through a natural infection.
“Fortunately, some vaccine candidates seem to do exactly that.”
But the reinfections likely meant that any hope of natural herd immunity “would not be possible,” Iwasaka said.
“Based on what we know about Covid-19, it would be too dangerous to try to achieve herd immunity through natural exposure to this virus, as it can be lethal or harmful in people of all ages.”
There is also the grim prospect of so-called antibody-dependent enhancement, when the antibodies actually make subsequent infections, such as dengue fever, worse.
While there is currently no evidence that it occurs with Covid-19, Shaman said he doesn’t know of anyone who can rule that out.
– Covid-19 ‘will never go away’ –
While many governments base their hopes for a full economic recovery on a vaccine, Van der Hoek said there may never be a single fully effective Covid-19 security device.
“The problem with coronavirus antibodies is that they fade very quickly and you can get re-infected with the same strain,” he said.
“So you may need repeat vaccinations (Covid-19) all the time.
“It will never go away. There is no way we can get rid of it. It will stay with us for the rest of humanity.”
© 2020 AFP
