A public health laboratory in Nevada has reported the first confirmed coronavirus reinfection in the United States, and the first in the world known to have brought on severe symptoms.
The first three confirmed reinfections in the world were reported this week, one in Hong Kong and two in Europe, all mild.
Reinfection does not surprise researchers, given the millions of cases around the world, but it is not yet clear if such cases — particularly severe ones — are anomalies or will prove common.
The patient is a 25-year-old man in Reno who apparently experienced a second bout of infection just 48 days after his first, according to health officials in Nevada.
Experts have said that even low levels of antibodies and T cells in response to infection should last for a few months and provide some protection against the virus, which appears to have been borne out in the other confirmed reinfections.
The patient in Nevada had a sore throat, cough, nausea and diarrhea starting on March 25. He tested positive on April 18, recovered by April 27, and tested negative twice. He began to feel unwell again on May 28, and three days later sought help for a similar set of symptoms.
He was hospitalized on June 5 for shortness of breath and needed oxygen; an X-ray showed the “ground-glass opacities” typical of Covid-19.
Researchers genetically sequenced the viruses from each bout, and found they were too different to be accounted for by an extended first illness. The findings have been submitted for consideration to the Lancet Infectious Diseases journal.
Mark Pandori, the director of Nevada’s state lab, said it wasn’t clear why the second bout was more severe. “There may be a biological reason for that, but we can’t sure at this time,” he said.
The researchers did not test the man for antibodies after the first illness, but found that he had them after the second.
Some experts said the severe symptoms could mean that the patient had not developed antibodies after the first infection, or that his immune response was overpowered by a massive dose of virus the second time. It is also possible that he suffered antibody-dependent enhancement, in which the immune response may worsen symptoms on a second encounter.
The findings highlight the need for widespread testing and viral sequencing, said Angela Rasmussen, a virologist at Columbia University in New York who was not involved in the work. “You really are going to need to look at a lot of these cases to try to start to narrow down which hypothesis is probably right,” she said.
