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Some of the patients with coronavirus were considered to have recovered, but then upon repeated testing they found a positive reaction. Usually, after coronavirus infections that cause colds, immunity develops. What is the difference between the causative agent Covid-19?
One of the first cases that alerted physicians was a man from Tokyo over the age of 70.
In February, he fell ill with Covid-19, was hospitalized in the infectious diseases ward, but successfully recovered, returned to normal life, and even traveled by public transport.
However, after a few days, his condition worsened again, his temperature rose and he had to return to the hospital.
According to the Japanese television channel N-H-K, he again underwent testing for coronavirus and, to the amazement of doctors, the reaction was positive.
Although this is not the only case in Japan, re-infection or the return of coronavirus is observed in a minority of cases. However, their number is still quite noticeable, and virologists still do not understand why this is happening.
The virus is back
Luis Enwanes, a virologist at the Spanish National Center for Biotechnology, told the BBC that at least 14% of patients who have recovered from coronavirus have a positive reaction when re-tested.
He believes that this is not about re-infection, but about a new reproduction of the virus in the body of an already ill person.
“My explanation, among many other possible ones, is that, on the whole, this coronavirus causes immunity to it in the population, but this immune response in some people is weak,” says Enhanes. “When this immune response slows down, the virus, which remains in the body returns. “
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According to experts, about 14% of patients tested on Covid-19 with a negative result, later a positive result reappears
The virus remains in the body
Some viruses are able to persist in the body for three months or even longer.
“When a patient undergoes a test and first shows a positive and then a negative reaction, doctors usually assume that he has developed immunity and that the symptoms of the infection should not recur,” says Enhanes. “But some pathogens may remain in tissues that are less susceptible exposure to the immune system. “
And in the causative agent of Covid-19 virologists, the fact that positive test results appear so soon after a visible recovery is alarming.
Scientists at a loss
We know that the human immune system reacts differently to various infections.
For example, in the case of measles, a single vaccination in early childhood is usually enough to acquire lifelong immunity.
However, in some countries, health authorities recommend revaccination at a certain age using a more modern vaccine.
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There are other viruses against which vaccines are not so effective, and therefore, repeated vaccinations must be carried out regularly.
Due to the mutation of the influenza virus, for example, such vaccination must be repeated every year.
Trying to figure it out
The new coronavirus causing Covid-19 is still not well understood, and scientists have not yet determined the nature of reinfection.
Isidoro Martinez, a fellow at the Charles III Health Institute in Madrid, believes that although re-infection with coronavirus is possible, the strange thing is that with Covid-19, a positive response to the virus appears so quickly after a negative one.
“If long-term immunity does not occur, then during the subsequent epidemic, after a year or two, you will again get an infection. And this is normal,” Martinez says. “But it’s rare to re-get the virus just transferred by a person. As far as we know, this the coronavirus does not change and mutate as fast and fast as the flu virus. “
Temporary virus activation
His explanation is close to the point of view of Enhanes.
“Probably those patients who show a positive response to coronavirus shortly after a negative one have a temporary activation of the infection before it is completely eradicated,” says the virologist.
However, both experts emphasize that additional studies are required to understand the nature of the Covid-19 virus.
In response to a request from the BBC, the Pan American Health Organization emphasized that the causative agent Covid-19 is a “new virus that we learn more about every day,” and so far there is no way to explain the cases of reinfection with full certainty.
However, research by scientists in this direction continues.
This article is written in response to readers’ questions about coronavirus.
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