A Nevada man was reinfected with the coronavirus — the first confirmed case in the US — and the second time was worse

• A Nevada man was infected for a second time with COVID-19 one month after recovering from a first bout, a new study confirmed.
• The case has a “significant” impact on how we understand immunity, one of the authors told the BBC.
• The 25-year-old man — who had no underlying conditions — suffered worse symptoms second time around, the study said.
• It is the first such confirmed case in the US, and one of only a handful worldwide. Other reinfection cases have been in Belgium, the Netherlands, Hong Kong and Ecuador.
• Visit Business Insider’s homepage for more stories.

A Nevada man who had already gone through a bout of COVID-19 was infected a second time with even worse symptoms, doctors have confirmed. 

They believe it is the first documented case of reinfection in the US, a rare occurrence that nonetheless shows that having had COVID-19 does not automatically confer immunity.

The 25-year-old’s case was reported in the peer-reviewed journal The Lancet Infectious Diseases, which outlined how the man, from Washoe County, first got his symptoms on March 25. 

Suffering from a sore throat, a cough, headache, nausea and diarrhea, he attended a community testing event on April 18 and was found to be positive. He had no underlying conditions or immune weaknesses. After self-isolating for nine days, his symptoms receded and he got well again. 

He took two tests in May, both of which came back negative. But two days after his second negative test, he began to feel unwell again, and a test on June 5 found him to be positive — this time with symptoms that sent him to the hospital. The man has since recovered.

Symptoms were worse second time around

Differences in the genetic sequencing of the virus showed that the new infection was not simply the original, dormant infection flaring back up, but a new one, according to the Lancet.

The chances of the same strain mutating in a single person in that time are "remote," the report said. It also ruled out the possibility that the man had been infected with both strains but that one had lain dormant until later.

The Lancet Infectious Diseases report confirms early, non-peer reviewed findings published in an August online preprint.

Second time around, the man was found to be short of breath and hypoxic — short of oxygen in the blood. He was sent to the emergency room for oxygen, the report said.

It's still unclear why the second infection was worse than the first, but the report's authors said there were three possible reasons:

1. He could have just had a higher dose of the virus on the second infection.
2. The second virus could have been a stronger version.
3. The immune response from the first infection made the second infection worse, the BBC reported. 

There's a lot still to know about coronavirus immunity — despite Trump's tweets

Discussion of immunity after infection has had even more intense interest than usual since President Donald Trump's doctors announced that he has recovered from the virus, as Business Insider's John Haltiwanger reported. 

The president has claimed multiple times that he is now "immune" — a claim that Twitter marked as "misleading." As Business Insider's Morgan McFall-Johnsen has reported, the science behind this is far from cut and dried. 

The Lancet Infectious Diseases study findings have "significant" implications for how we understand immunity, Dr Mark Pandori, associate professor of pathology at the University of Nevada and a co-author of the study, told the BBC. 

"Our findings signal that a previous infection may not necessarily protect against future infection," he said.

Professor Paul Hunter, professor of medicine at the University of East Anglia, told the BBC the findings were "very concerning."

But he pointed out that we would have heard by now if cases like this were common. 

There have been only a handful of confirmed cases of reinfection with the virus — a man from Hong Kong was announced as one such case in August, followed quickly by two more such cases in Belgium and the Netherlands. An Ecuadorian reinfection has also been confirmed, according to the study. 

"It is too early to say for certain what the implications of these findings are for any immunization programme," Prof Hunter told the BBC. "But these findings reinforce the point that we still do not know enough about the immune response to this infection."