A cancer survivor battled COVID-19 for a record-breaking 335 days – the longest ever documented case of the infection. 

The 47-year-old woman was first hospitalized at the National Institutes of Health (NIH) campus in Bethesda, Maryland, in the spring of 2020. Just one month shy of a whole year later, she was still testing positive for the virus, according to Science News. Her case is published as a pre-print on MedRxiv, which is yet to be peer-reviewed.

Having survived lymphoma three years earlier, her treatment left her with very few B cells – immune cells that produce antibodies – so she was more susceptible to a worsened, elongated infection.

Only in April of this year did the patient’s symptoms start to ease, and she began testing negative for COVID-19. The majority of people stop experiencing symptoms after an average of 10 or 11 days, according to the ZOE COVID Symptom Tracker, an app designed for people to self-report their symptoms. Just 5 to 10 percent of people go on to have symptoms that last longer, for several weeks or months, making this case somewhat of an anomaly.

“I’ve never heard of a transplant patient with flu for a year,” Dr Veronique Nussenblatt, an infectious disease specialist at (NIH) who treated the patient, told Science News. “That’s a really long time.”

Nussenblatt and colleagues initially believed that the continued positive COVID-19 tests were the result of harmless viral fragments lingering in the body after the infection had cleared. However, when her viral load, which had previously been very low, spiked again this March, doctors decided to sequence its genome, hoping to answer some of their questions. Was this the same, protracted infection that her body had failed to clear? Or had she become reinfected with another strain of the virus?

The results showed that the coronavirus in the patient’s system was very similar to the one she was carrying ten months prior – one of the first versions of SARS-CoV-2, which was no longer circulating by this time. 

“It was the same virus,” Dr Elodie Ghedin, a molecular virologist at NIH and author of the study, told Science News.

Sequencing also revealed two genetic deletions that could explain how the virus evolved as it was combatted by the patient’s weakened immune system. The first was a mutation of the spike protein, which the virus uses to enter cells. The second deletion, more interesting the team say, lay just outside the spike protein sequence and was much larger.

Such mutations give rise to new variants, allowing the virus to evade our immune responses and continue to make us sick. Chronic infections in immunocompromised individuals, as described in the current study, can help to drive this by facilitating recurrent rounds of viral replication countered only by a partial immune response to which the virus is constantly evolving. The alpha variant, for example, may have first appeared in an immunocompromised individual.

Preventing immunocompromised people from getting infected is, therefore, very important to limit the chances of the virus mutating into a new variant – and, of course, to protect their health. 

Thankfully, in this story, the ending is a happy (albeit well overdue) one. After multiple negative tests, Nussenblatt declared the infection finally gone. She told Science News that the two Facetimed this summer and that her patient was “walking on the beach”, eager to put her record-breaking ordeal behind her.