Researchers from the University of Nevada, among others, said the level of immunity from infection is unknown, and therefore coronavirus reinfection “is not well understood.”
The findings, published in The Lancet Infectious Diseases, described the Washoe County resident’s two positive nasal swab tests for SARS-CoV-2, the virus causing COVID-19 disease. He first tested positive at a community testing event on April 18, and again on June 5 with a more severe case requiring hospitalization, and two negative tests thereafter.
The patient started showing symptoms on March 25, including a cough, nausea, headache, fever, and diarrhea, per the report. There was no history of underlying conditions or immunocompromise. The symptoms came back on May 28, and the man was hospitalized on June 5 due to hypoxia and shortness of breath. He was on oxygen support and chest X-rays showed signs of bilateral viral pneumonia.
An analysis of the swab specimens revealed “genetically significant differences,” which suggested the man was infected on two separate instances by variant strains. “Previous exposure to SARS-CoV-2 might not guarantee total immunity in all cases,” study authors wrote.
The patient gave written permission to publish the report.
Other cases of reinfection have been reported in Hong Kong, Belgium, the Netherlands, and Ecuador, though only the Ecuador case also reported a more severe second case, researchers noted.
“The mechanisms that could account for a more severe secondary infection can only be speculated,” study authors wrote, theorizing that it was a higher dose of the virus or a more virulent version, among other speculations.
“It is possible that we have reported a case of continuous infection entailing deactivation and reactivation,” authors continued. “However, for such a hypothesis to be true, a mutational rate of SARS-CoV-2 would be required that has not yet been recorded.”
The authors said the findings may have implications for vaccination.