Traces of Covid remain in the blood for up to 14 months

In the United States, scientists from the University of California and Harvard Medical School discovered that, after Covid-19, some viral particles of the SARS-CoV-2 coronavirus can be found in the blood for up to 14 months. Quite possibly, these fragments are related to long Covid, that is, the lasting symptoms of the disease, such as fatigue and mental fog.

“The persistent symptoms among some individuals who develop Covid-19 have led to the hypothesis that SARS-CoV-2 may, in some way, persist for long periods after acute infection”, state the authors, in an article published in the journal The Lancet Infectious Diseases.

In fact, analyzes of plasma from people who have had Covid-19 confirm this idea, indicating that viral particles persist in the blood. However, it is not yet known how they are related.

Covid-19 viral particles

In the study, North American researchers analyzed frozen plasma samples from 171 adults who had Covid-19 — the blood was collected in another research, during 2020. These samples were obtained in three different periods: 3-6 months, 6-10 months and 10-14 months after the acute phase of the disease. This generated a total of 660 samples.

According to the researchers, 42 people (25% of those recruited) had viral particles in at least one of the samples. In extreme cases, this recurrence lasted 14 months. The most common viral particle was the Spike (S) protein, found in the virus membrane.

“Our data provide strong evidence that SARS-CoV-2 somehow persists for up to 14 months after acute infection,” the researchers explain. Among the possible explanations for this fact is the possibility that there are viral reservoirs, hidden from the immune system, that maintain the production of the virus — these reservoirs have yet to be found, but clues to them have already been located.

Furthermore, what scientists discovered is that the more severe an infection was, the greater the chances of the person having these resistant viral particles in their blood. For example, the risk is higher in those who have been hospitalized. They are also more likely to develop long Covid.

Cause of long covid?

Regarding the possible link with long Covid, the authors state that “these findings motivate a demand for urgent research into the clinical manifestations of SARS-CoV-2 persistence, specifically whether it is causally related to post-acute chronic symptoms (e.g. e.g., fatigue, pain, and cognitive difficulty) or to discrete incident complications (e.g., cardiovascular events)”.

Health risk

It is interesting to note one of the limitations of the study: the sample collection period. In 2020, no one had been vaccinated and people were exposed to the covid-19 virus for the first time — reinfections were not yet common, as they became throughout the pandemic.

This means that discoveries associated with viral particles and the possible relationship with long Covid may no longer be as frequent at present. As most of the population has defenses against the Covid-19 virus, the disease may behave differently, which indicates the need for additional studies.

Source: The Lancet Infectious Diseases

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