Scientists in Nevada are the latest to report a likely case of reinfection from the coronavirus that causes covid-19, with genetic evidence backing up their claim. While it remains to be seen whether reinfection will be a common phenomenon, this newest case suggests that a second infection can cause more severe illness than the first, even in young and seemingly healthy people.
The report was released as a preprint by The Lancet on Thursday, meaning that it hasn’t undergone the typical peer-review process as of yet.
According to the report, the patient is a 25-year-old resident of Reno, Nevada who tested positive for the novel coronavirus, SARS-CoV-2, in mid-April via a standard RT-PCR test. In late March, the man began feeling symptoms consistent with covid-19, such as sore throat, cough, headache, nausea, and diarrhoea. He isolated and reported feeling better by April 27; he also tested negative for the virus twice over the next month.
However, in late May, he began feeling sick again, and by May 31, he sought medical care with a self-reported fever, headache, dizziness, cough, nausea, and diarrhoea. He was sent home after a chest X-ray, but five days later, he went to a primary care doctor and was found to be oxygen deprived (hypoxic). He was then hospitalised. While in the hospital, he needed oxygen support and developed muscle pain, cough, and shortness of breath; an X-ray indicated that he had developed pneumonia. When tested for the virus, he again tested positive on RT-PCR, and an antibody test soon after also came up positive.
The researchers conducted a genetic sequencing of the virus found in the patient during those two events. The scientists found evidence that the two strains were genetically different enough from one another that it’s unlikely the man was carrying a persistent infection. They also investigated and ruled out the possibility of lab contamination being the source of either positive test result.
“Unlike the Hong Kong study, they actually did some forensic analysis to make sure that it wasn’t the result of contamination or a sample mix up, so that’s good.” Angela Rasmussen, a virologist at Columbia University who is not affiliated with the study, said by phone. “I’m pretty convinced by what they presented that it is a legitimate reinfection.”
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There have been at least three other reports of reinfection with similar genetic evidence, in Hong Kong, the Netherlands, and Belgium. These events aren’t necessarily surprising, given that other human coronaviruses can reinfect people after a certain period of time has passed. But experts have cautioned that widespread reinfection happening so soon into the pandemic is unlikely and that reinfection in general may be rare.
The authors of this report similarly state that reinfection may be a rare event. But what makes this case more concerning is that the man experienced a more severe illness the second time around, unlike the other reports of reinfection so far, in which the patients experienced no or mild symptoms from their second infection. And the authors couldn’t find any clear reason as to why that happened, such as a weakened immune system. The man contracted the second infection at the same time as another household member who tested positive, but it isn’t known whether the two cases were connected or in which direction transmission might have occurred.
According to study author Mark Pandori, the patient has since been discharged from the hospital, but Pandori couldn’t share his current health status.
There are crucial details missing that would help us better understand how and why reinfection happens. Importantly, the man wasn’t tested for antibodies during the first infection. So it’s possible a lack of antibody production during the initial infection (a rare but not unheard-of occurrence) may have left him more susceptible to the second infection. But we simply don’t know one way or the other.
“None of these reports of reinfection can really tell us anything about how common this is or about immunity and the role that it might play in all of this,” said Rasmussen.
As Pandori notes, though, few people were tested for antibodies in the U.S. in April. And to this day, antibody testing often isn’t part of the routine screening process for patients. According to Pandori and his team, it’s the continued limitations in testing availability and the lack of wide-scale genomic testing of patient samples in the U.S. and elsewhere that will make understanding reinfection all the more difficult.
Rasmussen said we could do a better job of tracking these cases via prospective studies that keep a close eye on patients and regularly test them over time to catch possible reinfections.
“But that’s going to be a problem, considering how the Centres for Disease Control and Prevention has advised less testing,” she added, referring to a recent change in guidance by the agency that discouraged people with a known exposure to the virus but no symptoms from getting tested. “If we’re not testing people widely, especially asymptomatic people, then we’re going to identify fewer cases, and we’ll have fewer opportunities to enroll people in a prospective study like that. And we’ll have fewer opportunities to actually sequence the virus from people who are infected, whether it’s their first infection or their second.”
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Of course, it also remains very possible that reinfection will be a fluke during this pandemic, with reinfection causing worse illness rarer still. But for people who have survived their initial bout with the virus, Pandori said, these cases should emphasise why it’s still important for everyone to be vigilant about covid-19.
“As of this moment, this and similar cases are a reminder that there is no such thing as ‘invulnerability’ just because you were infected and, perhaps, if you are vaccinated,” Pandori, who is also director of the Nevada State Public Health Laboratory and an assistant professor at the University of Reno, said in an email. “Care and vigilance that include masks and distancing and washing hands frequently are meaningful for everyone still. If there are more such cases, then deeper research can be done to see if there are any other significant implications, such as something specific to the biology of this agent.”