COVID-19 reinfection case 'no cause for alarm,' experts say


The University of Hong Kong reported the first confirmed COVID-19 reinfection on Monday: that of a 33-year-old who contracted it five months after his first infection. The patient initially tested positive for the virus on March 26, displaying classic symptoms such as cough, sore throat and fever. His symptoms disappeared days later and, by April, he had tested negative for the virus.

But according to the researchers, he tested positive for the virus again, on Aug. 15, during a routine screening following a trip to Europe. Through genetic sequencing, the researchers were able to locate more than two dozen differences — more than could occur by natural mutation of one infection — between the two strains the man contracted. This allowed them to rule out the possibility that he tested positive due to lingering viral fragments, which has been suggested in other cases.

Angela Rasmussen, a leading virologist at Columbia University, was one of many infectious disease experts to tweet about the report — and to urge caution when interpreting it. Rasmussen pointed out that the news came in the form of a press release (the researchers say it has been submitted to the journal Clinical Infectious Diseases) and has been neither peer-reviewed nor published. “While I agree that the sequencing data they are reporting here suggests reinfection, there are a lot of questions that can’t be answered with just a press release,” she tweeted.

On top of the unanswered questions, there are aspects of the news that she and other experts seem to suggest are both predictable and promising. Here are three important things to know.

Hong Kong has reported the first probable case of COVID-19 reinfection, but experts say it's no reason to panic. Here, a worker prepares a collection tube in California. (AP Photo/Wilfredo Lee)
Hong Kong has reported the first probable case of COVID-19 reinfection, but experts say it's no reason to panic. Here, a worker prepares a test collection tube in California. (Wilfredo Lee/AP)

The patient was asymptomatic the second time, which may signal immunity

Although the 33-year-old tested positive for COVID-19 a second time, multiple experts have pointed out that he showed no symptoms — which may be good news. “This is no cause for alarm — this is a textbook example of how immunity should work,” tweeted professor Akiko Iwasaki, an immunologist at the Yale School of Medicine. “While immunity was not enough to block reinfection, it protected the person from disease.”

Dr. Vincent Rajkumar, a professor of medicine at the Mayo Clinic, agreed. “Immunity is protecting your own body from having severe disease the second time around,” tweeted Rajkumar. “The immune system is primed and better prepared. That’s immunity.”

In an email to Yahoo Life, Rasmussen noted that the man had tested negative for antibodies initially, but that the lack of symptoms a second time might mean some remained. “It’s very possible he did have some immunity that was below the threshold for detection using the Abbott antibody test,” Rasmussen writes. “If that’s the case, then immunological memory would kick in after being infected the second time and rapidly control the infection, resulting in asymptomatic disease.”

Of nearly 24 million virus cases worldwide, one confirmed case of reinfection makes it very rare

At a press conference Monday, experts from the World Health Organization attempted to allay fears surrounding the news from Hong Kong, noting that one case proves little about the overall behavior of the virus. “What I think is really important is that we put this into context,” said Maria Van Kerkhove, an epidemiologist and WHO’s COVID-19 technical lead. “There have been [nearly] 24 million cases reported to date, and we need to look at something like this on a population level.”

Rajkumar tweeted that it’s likely “severe reinfection will be very rare,” and that “reinfections won’t cause a repeat of the pandemic,” adding “NO need to panic.” Rasmussen echoes the sentiment. “It’s hard to assume larger implications based on a single patient,” she tells Yahoo Life. “I tend to be more circumspect about extrapolating results from one individual case to entire populations of people, so my opinion is that it’s important to look for more of these cases, but until we know how common they are, we should hold off on making sweeping conclusions about herd immunity and vaccine efficacy.”

Reinfection is not uncommon for human coronaviruses

The researchers from Hong Kong pointed out in their press release that “reinfection is common for ‘seasonal’ coronaviruses” and that it can occur despite a “static level of specific antibodies.” Van Kerkhove expanded on the importance of this in the WHO press conference. “With our experience with other human coronaviruses, we know that people have an antibody response for some time, but it may wane,” said Van Kerkhove.

She noted that reinfection with other coronaviruses — and, likely, this one — does not mean the body has not built immunity. “I really don’t want people to be afraid,” said Van Kerkhove. “We need to ensure that people understand that when they are infected — even if they have a mild infection — that they do develop an immune response.”

Overall, Rasmussen says, the study simply highlights the need for more research. “This is the blurry area between susceptibility to infection and susceptibility to disease,” she says. “Without more data from more reinfected patients, we can’t really do much besides speculate and hypothesize.”

For the latest coronavirus news and updates, follow along at According to experts, people over 60 and those who are immunocompromised continue to be the most at risk. If you have questions, please reference the CDC’s and WHO’s resource guides.

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