Can you catch COVID-19 twice? Cases in Korea

A lab member swabbing a petri dish. He may be trying to answer the question "Can you catch COVID-19 twice"?
Many lab techniques are used to test for COVID-19. Testing inaccuracies may contribute to observations in South Korea.

Some of the earliest questions around COVID-19 were “can you catch COVID-19 twice” or “can you get reinfected”? From the beginning, our answers have been:

  • It is unlikely to get re-infected from SARS-CoV-2.
  • But we can’t say it’s impossible because it is too early to tell in large populations.

What’s new in Korea? Are reinfections happening there?

South Korea has become word renowned for its widespread COVID-19 testing efforts. They quickly implemented scalable quarantine and contact tracing infrastructure. They are now using their data to shed light on how many people are testing positive again after recovering from COVID-19. Importantly, they can trace contacts of these individuals to determine the risk they pose in COVID-19 spread.

Unfortunately, we are awaiting published studies providing clearer statistics on their observations. Preliminary results (using viral PCR) were shared on the internet:

  • South Korea has recorded 292 people who tested positive → negative → positive again.
  • Earlier this month (when the that number was 137 people):
    • 61 had mild symptoms.
    • 72 had no symptoms.
    • 4 pending results.
    • No secondary infections were observed (meaning none of these positive → negative → positive individuals had infected healthy people yet).
  • Average 13.5 days between patent discharge and the repeat positive test result.

So can you catch COVID-19 twice?

There are several possibilities explaining these people who have retested positive for COVID-19 after a negative test:

  • “Dead” viral particles: the PCR test will detect viral RNA even if the virus is no longer infections (it’s like identifying the bones of a dead dinosaur).
  • Inaccurate testing yielding false negatives or false positives: possible. False negatives at time of hospital discharge or false positives on retesting could yield these observations. This is concerning because COVID-19 tests have been notoriously variable. In the USA this is possibly from rushed emergency FDA actions.
  • True COVID-19 reinfection: unlikely but cannot 100% exclude. Some individuals mount weaker SARS-CoV-2 antibody responses making this not impossible.
  • Chronic COVID-19 infection: this would mean that SARS-CoV-2 lives in the human body for an extended period of time (like tuberculosis). We have little evidence to support this theory.
  • Detection of a new coronavirus strain (eg a mutated strain): little evidence to support this currently in Korea.

Importantly, during the contact tracing investigations in South Korea:

“No new case has yet been confirmed that resulted from exposure to the re-positive cases (during the period in which they were re-positive). The contacts are still under monitoring.”

So it sounds unlikely that you can get COVID-19 twice, right?

That is correct based on our available Korean preliminary studies. South Korea is well poised to contribute valuable data on this topic because of their strong testing and contact tracing infrastructure. We desperately need to know if any of these patients who have retested positive have spread COVID-19 to contacts. If they can’t spread infectious disease, it would appear unlikely that COVID-19 reinfection poses a serious concern at this time.

Let’s hope that’s the case! That would allow immunity to assist us in our return to normalcy in the coming months.

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The information provided in this post in intended for general education. It is not medical advice. While I make every effort to provide the most up-to-date information, please note that new data is continuously becoming available and may change the conclusions I present here.

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