Nevada man's COVID-19 reinfection is 'yellow warning light' about broader coronavirus risk

An otherwise healthy 25-year-old Nevada man is the first American to catch COVID-19 twice, with the second infection being worse than the first.
He has recovered, but his case raises questions about how long people are protected after being infected with the coronavirus that causes the disease, and possibly how protective a vaccine could be.
"It's a yellow warning light," said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical School in Nashville, Tennessee, who was not involved in the research.
Respiratory infections like COVID-19 do not provide lifelong immunity like measles infection. Dr. Paul Offit, an infectious disease expert at Philadelphia Children's Hospital, said he wasn't at all surprised that people could become infected twice with the SARS-CoV-2 coronavirus.
It's too early to know if the man from Washoe County, Nevada, who has had no known health problems other than double infection, said it was highly unusual or if many people could easily become infected with SARS-CoV-2 more than once, said Conductor.
"There is hardly an infectious disease doctor in the country who has not met a patient who thinks they have had a second infection," he said. "We don't know whether that's true or not. There are many respiratory infections."
How rare is it?
At least 22 reinfection cases have been documented around the world since the pandemic began. However, it is unclear how many cases have actually occurred and how common they can be in people who do not even know they are infected.
"It could be a one-in-a-million event, we don't know," said Akiko Iwasaki, an immunologist at Yale University and an investigator at Howard Hughes Medical Institute, who commented on the study.
With millions of people infected, it's hard to know if case studies like the new one represent very rare events or the tip of an iceberg, she said. "It is possible that the vast majority of people are completely protected from re-infection, but we do not measure them because they do not come to the hospital."
Also, many people don't know they are infected the first time, so it is difficult to tell if they will get infected again.
In one of the most recent cases, a Hong Kong man only knew he was infected again as he was caught on a routine screening when he returned from outside the country months after an infection was cleared and tested negative.
One reason there may be undocumented cases of reinfection: it's hard to prove, said Mark Pandori, a pathologist at the University of Nevada, Reno School of Medicine and lead author on the new study.
His team coordinated with members of the Washoe County Health District at the start of the pandemic to look for recurring infections. They had the benefit of on-campus sequencers as well as microbiologists, he said. And they were lucky enough to find someone who had been tested both times when it was infected and cleared in between.
Why his infection was worse the second time remains unclear, said Pandori, director of the Nevada State Public Health Laboratory. "I can't tell you if it tells us anything special about the biology of this virus."
According to a genetic analysis of the man's infections, the man caught a slightly different version of the virus for the second time. It is possible that the second version was more dangerous, although there is no evidence to support it, or that it was just so different that his body did not recognize it, the paper said.
Effects on vaccination
According to Iwasaki, the study raises questions about how long immunity lasts after natural infection. Protection with a vaccine is likely very different, she said.
"Vaccines can be designed to induce much higher levels of antibodies and much longer-lasting immunity," she said. Just because the natural infection won't protect you doesn't mean the vaccines can't. It's a separate topic. "
Offit, also a vaccines expert at the University of Pennsylvania's Perelman School of Medicine, believes protection from vaccines is likely to last at least a year or two.
Protection from infection or vaccination isn't 100% perfect until it goes away completely, he said. Instead, protection gradually wears off, so someone exposed to a large dose of the virus can be re-infected within months while others could be protected for years, Offit said.
It's also possible that the Nevada man has an undiagnosed problem with his immune system. "He should probably be seen by an immunologist," Offit said.
The duration of an infection protection remains one of the most important open questions about the virus.
Infected twice with an interval of two months
The Nevada man, considered an indispensable worker, felt sick in late March, with a sore throat, cough, headache, nausea and diarrhea. His workplace was hit by an outbreak at the beginning of the pandemic before safety measures like masks could be put in place, said Heather Kerwin, senior epidemiologist for the Washoe County Health District and co-author of the paper.
He went for testing on April 18 and his coronavirus infection was confirmed.
On April 27, he reported that his symptoms had all subsided and he was feeling fine. At this point, however, employees had to test negative for COVID-19 twice before being allowed to go back to work, Kerwin said. So he stayed isolated at home.
A month later, he felt bad again. At the same time, there was an outbreak that employed one of his parents, also a key worker, Kerwin said.
On May 31, he went to an emergency center and reported a fever, headache, dizziness, cough, nausea and diarrhea. On June 5, he went to a doctor who found his oxygen levels dangerously low and had him taken to the hospital. Again, the man tested positive for the virus even though he still had antibodies to the virus in his bloodstream, Kerwin said.
Genetic differences between the viruses responsible for each of his infections suggested that he was infected twice separately. The virus doesn't mutate quickly enough within a single person to explain the differences between the two infections, the researchers found.
A parent who lived with the man also caught COVID-19 and was diagnosed on June 5.
The newspaper reports that the man may have been infected again from being exposed to a higher dose of the virus the second time, possibly from the family member.
His cough persisted and he suffered from shortness of breath and mental fog and was oxygenated for six weeks after the second infection, Kerwin said. He has now fully recovered.
Mark Pandori, pathologist
Reinfections imply that the so-called herd immunity cannot only be achieved through a natural infection. If a natural infection only protects for a few months, it is impossible for enough people to be protected at the same time to achieve herd immunity.
The moral of the case study, co-author Pandori said, is that even people already suffering from COVID-19 need to protect themselves by wearing a mask, avoid large gatherings, wash hands frequently, and maintain social distance.
"You're not invulnerable for that," said Pandori. "In fact, it could get worse the second time."
Contact Karen Weintraub at and Elizabeth Weise at
US TODAY health and patient safety coverage is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide any editorial contributions.
This article originally appeared in the US TODAY: COVID Reinfection: Viruses Can Occur Twice, Worse Second Time

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