Science

Covid-19: virus outbreaks more frequent than expected – Science et Avenir

In early August 2022, US President Joe Biden tested positive for Covid again when he believed he had already recovered from the coronavirus infection after testing negative two days in a row. A few days later, his wife Jill Biden also suffered from a similar phenomenon, testing positive just days after testing negative. In both cases, it was not a new infection, but a viral rebound after the same infection. A phenomenon that was considered rare and was associated with antiviral drugs, which in some cases could attack the virus without completely destroying it, allowing it to reappear after treatment. But a Harvard University study shows that these viral relapses are more common than previously thought, even in the absence of antiviral treatment. The study was posted online in a preprint (not yet peer-reviewed) on August 2, 2022.

Covid patients are tested daily for viral load and symptoms

The researchers studied the development of the infection in more than 200 adult patients with mild Covid (therefore not hospitalized), mostly unvaccinated. Participants were part of the control arms of three randomized clinical trials investigating monoclonal antibodies against Covid, meaning patients included in this study received placebo rather than treatment. Therefore, these patients were randomly selected (at the time of their enrollment in clinical trials). They were tested by PCR daily for two weeks and then on the 28th day. And they had to report their symptoms every day for 28 days. This very careful observation allowed the researchers to see in detail the evolution of the infection and its symptoms throughout the study.

So they highlighted that these viral rebounds, when a person tests positive again after being negative, affected 12% of patients (about 1 in 8). In most cases (73%), this relapse occurred within five days of receiving a negative test result and almost always lasts only one day (this occurred in 91% of viral relapses). This is probably why this phenomenon is rarely seen, except for very popular people like Joe and Jill Biden.

Rebound symptom seems to be more frequent

Symptoms can also show such a rebound, and this will be even more common than tests. In the study, 27% of participants noticed a worsening of their symptoms after seeing their severity decrease (about 1 in 4 participants). Moreover, in 10% of them, the symptoms returned even after their complete disappearance. On the other hand, cases showing virus recurrence in tests as well as in symptoms are much less common (2.2% of participants).

The authors propose several hypotheses to explain these viral rebounds. One possibility is that the virus has spread to multiple locations in the body, causing a range of symptoms to develop. In addition, these relapses can be explained by close infection with different variants of the coronavirus, but these co-infections are rare (much rarer than these viral relapses seem). Finally, coinfection with other viruses can also cause these recurring symptoms.

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