Researchers from the Pasteur Institute (France), the University of Sao Paulo and the Oswaldo Cruz Foundation (Brazil) have documented the case of a 38-year-old man who continued to test positive for Covid-19 for at least 232 days.
«Of the 38 cases we tracked, 2 men and one woman were atypical in the sense that the virus was continuously detected in their body for more than 70 days,» explains Marielton dos Passos Cunha, first author of the article, which has been published in the scientific journal Frontiers of Medicine.
This is not the first evidence that the virus can remain active for longer than expected even in patients with mild symptoms. In early 2021, other Brazilian researchers reported similar cases.
They analyzed 29 samples of nasopharyngeal secretion from patients who tested positive for Covid-19 on the tenth day after the onset of symptoms and inoculated them into cells grown in the laboratory. In 25% of cases, the viruses present in the samples were capable of infecting cells and replicating in vitro. Therefore, in theory, other people could become infected if they came into contact with the droplets of saliva expelled by 25% of these patients at the time of material collection.
The risk appears to be even greater for people with compromised immune systems. In an article published in June 2021, these same researchers described a case of infection that lasted at least 218 days. The patient was in his 40s and had undergone aggressive cancer treatment before contracting Covid-19.
Additionally, an article published in the New England Journal of Medicine in early December 2020 reported the case of a 45-year-old immunosuppressed man with an autoimmune blood disorder in which the virus continued to replicate for 143 days. And an article published in Cell at the end of December outlined the case of a leukemia patient in whom the virus continued to replicate for at least 70 days, even though she had no symptoms of Covid-19.
In this new study, the difference between women and men in the duration of viral activity was not significant (with a mean of 22 days and 33 days, respectively). As for the three atypical cases, the virus remained detectable for 71 days in the woman and 81 days in one of the two men. None of them had comorbidities and all had mild symptoms of Covid-19.
The other man continued to test positive for the coronavirus for 232 days (April to November 2020), after which he tested negative three times by PCR. He has had HIV, the virus that causes AIDS, since 2018, but has no detectable viral load thanks to antiretroviral therapy.
“Just because you are HIV positive does not mean you are more susceptible to other infections, as you have been on therapy since you were diagnosed. Its ability to respond to an infection by another agent is comparable to that of any other individual, and it did respond to the coronavirus when infected. It is not immunosuppressed, like cancer patients, people with autoimmune diseases or transplant recipients, for example”, explains Paola Minoprio, one of the leaders of the work.
According to the researchers, his seropositive status does not explain the long duration of his coronavirus infection. Many patients simultaneously infected with HIV and SARS-CoV-2 would need to be compared with a suitable control group to see if any genetic or host immune traits might be associated with such prolonged viral shedding.
The patient underwent weekly tests that detected the persistence of the infection, and virus samples were periodically sequenced to show that this was not a case of reinfection and that the virus was not only continuing to replicate, but was mutating.
The strategies used by the virus to escape the immune system during infection were traced, showing that the viral load decreased when there were more neutralizing antibodies, and that the virus was able to circumvent the body’s defenses to re-accumulate the load. The cycle repeated itself, forcing the production of more antibodies until the viral load dropped again.
«It is important to observe patients like this because we can learn more about how the virus mutates and which mutations can lead to variants of concern,» Cunha says.
The patient in the study was infected by the B.1.1.28 lineage, also called P1, which entered Brazil in early 2020. The researchers did not detect mutations in the virus isolated from the patient that could justify its classification as more transmissible or more resistant to the immune system.