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Is it possible to get sick from Covid again? And when can we talk about a new infection instead of a relapse? To rekindle the discussion about one of the most debated moments of this pandemic is the case of a 25-year-old Roman. positive for coronavirus in October and then again in December, one month after being cured. His case is sobering because it could be similar to some cases of reinfection, even if so far these are very rarely documented circumstances, in part because to be sure that it is a reinfection a genetic analysis of the virus that causes the first infection would be necessary. . and an additional analysis at the onset of the second disease to understand whether the new manifestation is caused by a different or mutated strain. Tests that are actually difficult to do and are often done in the context of scientific studies. In any case, the news of the new case registered in Lazio brings the issue back to the fore, providing some ideas to understand when it is possible to speak of reinfection and when of relapse.
The case of a 25-year-old Roman
“I started to feel bad in mid-October. tells the young woman to Ansa – but the first quick swab on October 13 was negative. As I was still feeling bad, I did a second molecular smear at the Fiumicino drive-in on October 20 and tested positive“The symptoms included severe pain in the muscles, with a low-grade fever, up to quite severe respiratory difficulties, so, however, hospitalization was not necessary and the patient was always followed at home by her family doctor. On October 30 , he underwent a new molecular swab at the Sant’Andrea hospital that tested negative. And on November 13, the second negative tampon arrived, at the drive-in theater in Santa Maria della Pietà. In recent days, however, the father has become ill with Covid-19, apparently due to a workplace outbreak, so “as a precaution – says the girl – in the family we all rub: I came back positive on the molecular test., I had a fever at 38 and a half and now I have muscle aches again “.
Second infection or relapse?
The history, according to the agency, does not really allow us to speak of reinfection or exclude that it is a relapse. First due to the lack, as mentioned, of genetic analyzes aimed at understanding the differences between the viruses that caused the infection (in fact, we know that there are several strains of the coronavirus Sars-Cov-2 in circulation and that in some cases a second infection). On the other hand, due to a possible reinfection, which could be explained by the development and duration of immunity after the first infection, in the case of the young Roman not verified by specific analysis of immunoglobulins and lymphocytes. A study recently published in Nature In fact, it has clarified the importance of the humoral response (antibodies) and the cellular response (T lymphocytes) in coronavirus infection, indicating that the protection mediated by antibodies depends on their concentration and that T lymphocytes are necessary if the levels of the antibodies are insufficient.
In the case of the 25-year-old, the only information available is on the reappearance of symptoms. about a month after remission. Therefore, a particularly short time interval and that, in the absence of other data, may suggest a relapse Like the one that, for example, can occur as a result of the flu, when we think we are cured and, instead, after a very short time we go back to bed.
The “negative” quick swab
Regarding the negative result of the first antigenic swab (“October 13 was negative“) it’s unclear what the exact time frame is between the day of suspicion of infection and the test, or if the decision to carry out the control was due to the appearance of symptoms or scruples, since the girl only reports that she has not been well since mid-October, probably a few days then the test.
This aspect, regardless of the sensitivity and specificity of the rapid swabs, which, in any case, should be used for population screening and not for the diagnosis of Covid, is essential since, like molecular tests, they also rapid test may fail if performed immediately after infection is suspected. In other words, the viral load may still be too low and not enough to be detected, thus making the test ineffective. One of the recommendations regarding tampons is in fact that of wait a week (five to seven days after exposure) before undergoing the control, and if the first test is negative, it is worth repeating it about 12 days after the initial event to avoid the possibility that the infection takes longer to manifest. .
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