The longest COVID infection lasted more than 600 days – Science

When the Omicron strain of SARS-CoV-2, the virus that causes COVID, was spreading around the world in February 2022, a man infected with the variant was hospitalized at Amsterdam University Medical Center. He was 72 years old and suffered from overlapping myelodysplastic and myeloproliferative syndrome, a combination of disorders that alter the proper production of blood cells, and lymphoma. Over the next 612 days, during which he was in and out of the hospital, the man continued to test positive for COVID. His case is the longest consecutive COVID infection documented, according to a recent report by researchers at the University of Amsterdam.

The report details the evolution of the man’s symptoms and treatment journey, and how the Omicron variant developed more than 50 new mutations during more than 20 months of infection. The report, which has not yet been published in a scientific journal, was presented during the last weekend of April at the Global Congress of the European Society of Clinical Microbiology and Infectious Diseases in Barcelona.

“Chronic infections and viral evolution are commonly described in the literature, and there are other cases of immunocompromised patients who have had COVID infections for hundreds of days,” says Magda Vergouwe, PhD candidate at the Center for Experimental and Molecular Medicine of the university and lead author of the report. “But this is a unique case due to the extreme duration of the infection… and with the virus remaining in his body for so long, it was possible for mutations to continuously develop.”

The man, who sadly later died due to complications from his underlying condition – not COVID in particular – was first admitted to hospital when he began experiencing respiratory symptoms of COVID, including coughing, breathing short and dangerously low blood oxygen levels. He had previously received three shots of the Moderna mRNA COVID vaccine, but his body contained no detectable antibodies. That’s likely due to the immune system-suppressing drugs he was taking to treat the lymphoma and blood disease, Vergouwe says. One of the drugs he was taking, rituximab, targets the abnormal B cells that cause cancer, but in the process it can also destroy their healthy counterparts, which are responsible for creating antibodies against infections.

Doctors prescribed several treatment regimens for COVID to the man, including sotrovimab, a monoclonal antibody approved by the European Medicines Agency (EMA). The man had no measurable clinical response to any of the treatments and could not safely discontinue any of the other drugs that could have altered their effectiveness.

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After about a month, however, the initial COVID symptoms subsided spontaneously and the man was discharged from the hospital, first entering a rehabilitation center and finally returning to his home to isolate. But he continued to test positive for COVID throughout the 20 months and at times developed new infections, such as bacterial pneumonia, that likely were complicated by COVID and required additional hospitalizations.

“It is important to note that he ultimately did not die from COVID-19,” Vergouwe says. “But he had it with him for a very long period of time until then, and that’s why we made sure to sample the virus in his body as much as possible.”

The researchers analyzed 27 nasal swab samples taken from February 2022 to September 2023 and detected more than 50 new mutations of the original Omicron strain that infected humans. Vergouwe says that while this number may seem shocking, mutations in the SARS-CoV-2 genome are expected to emerge more rapidly in immunocompromised people (the average mutation rate of the virus is estimated at two mutations per month per person). What makes these mutations unusual, she notes, is that their characteristics differ markedly from mutations seen in other people with COVID. The author hypothesizes that the exceptional duration of infection in this individual and his pre-existing conditions allowed the virus to evolve extensively and uniquely.

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But the 50 new mutations that emerged in this case are unlikely to spread worldwide, says David Wohl, a professor of medicine in the division of infectious diseases at the University of North Carolina at Chapel Hill, who was not involved in the research. Viral mutation is common; a virus that replicates in the human body rarely does so perfectly, and these slightly different versions are considered mutants. Sometimes the changes in the virus are not beneficial to its survival and are not perpetuated. Other times a mutant’s new feature is advantageous to the virus and can help it overcome an infected person’s immune response. The mutant becomes a greater threat and can transform into a variant of concern if it manages to jump from one host to another, acquiring new characteristics and defenses against antibodies.

In this case, the viral mutants did not have characteristics that increased transmission and are not documented to have infected other people. For mutations to spread successfully and become as insidious as the Omicron and Delta variants of SARS-CoV-2, a “perfect storm of negative events” needs to occur, Wohl says.

Prolonged SARS-CoV-2 infections in immunocompromised people are not particularly rare, Vergouwe says, and experts continue to study these cases to follow the development of mutations and better understand people’s immune responses.

The best ways people at all risk levels of severe COVID can protect themselves remain up-to-date on vaccines and wearing high-quality masks in crowded areas. “New variants can potentially emerge from immunocompromised people,” concludes Wohl. “But variants also emerge from other people who are not immunocompromised, because they pass the virus to each other. This is part of the nature of the pandemic and the way viruses naturally exist and, unfortunately, evolve.”

(The original of this article was published in “Scientific American”. Translation and editing by Le Scienze. Reproduction authorized, all rights reserved.)