Coronavirus: how a reinfection is detected and what are its consequences


In Argentina there could be cases of reinfection by coronavirus, but in the country the necessary studies are not carried out to confirm that it is a second condition Source: Archive

Aldana López is 26 years old and works as an administrator in a municipal health center in Tigre. In August he began to have a fever and headache. They swabbed her and she tested positive: she had coronavirus. Almost three months later the fever returned, the headache, he lost his smell and taste. They swabbed it a second time, and again the result came back positive.





Another similar situation is that of Amparo Castillo Marín, 22 years old. In August he had close contact with a confirmed case and, although he had no symptoms, they did a PCR test that confirmed that he was going through a Covid-19 frame. A few weeks later a blood test was done, in which the antibodies were detected. But this month he felt bad again. It was swabbed last week and the PCR test returned to detect coronavirus particles. Yesterday his isolation ended. Does this mean that in both cases there were reinfections?



“The problem is that to certify something that looks like a reinfection, you need information that is difficult to obtain. This means that the only way I can ensure that there was a reinfection is by comparing the genetic sequence of the virus that produced the first illness. and the genetic sequence of the virus that produced the second condition, and then verify that they were different strains. In this way, we made sure that the second positive swab was not because genetic traces were detected that remained from the first infection, “he explains Pablo Scapellato, member of the Argentine Society of Infectology (SADI) and head of infectology at Santojanni hospital.



In Argentina, tracing the genetic code of the virus is something that is not done on a large scale, unlike Europe, which has a database with the genomic sequence of the different strains that infected its citizens
In Argentina, tracing the genetic code of the virus is something that is not done on a large scale, unlike Europe, which has a database with the genomic sequence of the different strains that infected its citizens Source: LA NACION – Credit: Aníbal Greco

In Argentina, tracing the genetic code of the virus is something that is not done on a large scale, unlike Europe, which has a database with the genomic sequence of the different strains that infected its citizens. Thanks to this they were also able to verify that the strain that is causing havoc in England is a new mutation.


Without this information, it is not possible to determine whether the patient is experiencing a second coronavirus case, or whether the PCR test detected genetic remains that remained in the mucosa from the first infection. Those genetic remains may or may not be active.

“The PCR finds the genomic sequence of the virus, but it is not known if it is alive or dead. That happens to us with many other diseases that we diagnose with PCR. For example, a PCR for tuberculosis can test positive for years, when in reality the person it is already cured. In the case of the coronavirus, we also know that the presence of the viral genome can be detected for many weeks. To diagnose a reinfection with certainty is complex, but if a patient has already been infected, he must still maintain all the care “, adds Scapellato.

Catalina Semmartín is 50 years old. She was diagnosed with a coronavirus picture after swabbing it on July 8 and was discharged 15 days later. On the 3rd of this month she started to feel congested. “I thought it was an allergy, nor did I think it was going to be Covid. In the following days I had a fever, a sore throat, I lost my smell and taste. I went to the Austral Hospital and without swabbing they already told me that I had coronavirus again. But they did swab my mother, who had only been in contact with me and she tested positive, “says Semmartín.


Catalína Semmartín is 50 years old.  She was diagnosed with a coronavirus picture after swabbing it on July 8 and was discharged 15 days later.  But this month a swab tested positive again
Catalína Semmartín is 50 years old. She was diagnosed with a coronavirus picture after swabbing it on July 8 and was discharged 15 days later. But this month a swab tested positive again Credit: Courtesy: Catalina Semartín

Elena Obieta, infectologist and member of SADI, points out that, in Argentina, due to a cost-benefit logic, the swab was stopped when a patient is about to be discharged, so it is not known whether the person stopped having genetic traces of the virus.

“It was no longer determined that there is no infection. We believe that if a person was infected, even if they had mild symptoms that, in general, generate fewer antibodies, for at least three months they would not be at risk of being reinfected with the same strain Then there are patients who are carriers of the virus for a long time, have it in the mucosa and can be contagious for weeks. In the case of those who were effectively recontaminated by being in contact with another strain, the picture may be milder or more severe, but they spread like any other patient “, Obieta details.

Conrado Estol, a neurologist, points out that, worldwide, reinfections could occur in one or two percent of cases. “Although we may never find out what the real rate of reinfection of this disease is, because next year the vaccine will be applied massively. There is post-Covid syndrome, which are the cases in which virus particles were detected months later, but that does not mean that it is infectious, that the virus is active or that it is a reinfection, “says Estol.


In Argentina there could be cases of reinfection by coronavirus, but in the country the necessary studies are not carried out to confirm that it is a second condition
In Argentina there could be cases of reinfection by coronavirus, but in the country the necessary studies are not carried out to confirm that it is a second condition Source: LA NACION – Credit: Hernán Zenteno

The specialist adds that, to be sure that there is a reinfection, a genomic sequencing of the virus must be done, and that is done in Europe. For its part, the United States does not do it on a large scale either, so they have not yet detected the United Kingdom variant within the country.

“In Argentina we only do PCR, that is to say that we only confirm the presence of the virus and on top of that we test little. In Europe there is a specific database with the genomic sequencing of strains and they commented on this a lot now that they found the new strain in England In Uruguay, at the beginning, they sequenced 20% of the tests they did. In the United States, when they did, they saw that the Chinese virus was on the West Coast, but the one that circulated in Manhattan was the strain that arrived from Europe. ” , argues Estol.

In a review of the confirmed cases of reinfections worldwide, Estol highlights that of a 74-year-old man in Israel who had a first episode and was discharged without complications to the nursing home where he lived. Then he had a second episode of Covid-19, confirmed by PCR, in which it was also confirmed that the virus strain was different from the first infection. That patient was the first to die from a proven reinfection.

“The first known case of reinfection was that of a Hong Kong man who contracted the disease again after going to Spain. The second appeared in Reno, Nevada, another in Brussels. The one in Reno had a more severe picture than the one he had during the first infection and the one in Hong Kong had a very mild picture. So far there are 31 confirmed cases of reinfection, two of them died. The average interval between both infections has been 80 days. More than 2000 suspected cases of reinfection with 24 deaths. These numbers suggest a low incidence of reinfection among the total of patients with confirmed Covid-19 “, concludes the specialist.

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