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If someone had the virus, tested positive, then tested positive months later, is that person able to transmit?

Question: Still finding myself confused about test results / transmission ability….If someone had the virus, tested positive, then tested positive months later, is that person able to transmit?

Answer: We talked about the issue of potential reinfection in our Q&A of Q&A of 5/19. Short answer is: We still aren’t sure but most folks who test positive after apparent recovery are not contagious. Now for more detail…

When it comes to people testing positive for the virus after apparent recovery, we have three hypotheses (described more in Q&A of 5/19):

  1. They’ve become reinfected;
  2. They are experiencing reactivation of dormant virus; and
  3. The second round or positive results are false positive.

When I wrote the post 2 months ago, it was looking like hypothesis 3 was the most likely. Since then, we have a few additional case reports of reinfection/reactivation. For example, this paper published last month in the Journal of Infection describes reinfection/reactivation among 11 patients in France while this paper published earlier this month in the Journal of the American Geriatrics Society also describes reinfection or reactivation among 3 older women hospitalized in France. In both of these papers, reactivation was the preferred hypothesis for what was causing these patients to exhibit symptoms after apparent recovery — that is, their bodies had not fully cleared the virus and it made a resurgence. Thus far, the evidence still suggests that hypothesis 3 is most likely/common, followed by hypothesis 2. We still have no definitive data on anyone becoming reinfected (hypothesis 1).

I share all of this because it all has bearing on whether we would expect a person who tests positive after apparent recovery to be contagious. And thus far, the evidence points to two things: 1) since most people who test positive a second time are likely to fall into hypothesis bucket 3 — test is a false positive — they are not infected and cannot transmit the virus to others; and 2) for those (seemingly rare) folks who are exhibiting symptoms again and test positive a second time, we should consider them as possibly contagious and ask that they again self-isolate; health providers will also treat them as COVID patients in terms of protocols and the like.

Finally, I think this paper from Journal of Medical Virology offers a nice summation of the evidence (as of early June). And just yesterday the NY Times published this report that synthesizes current thinking on reinfection. (It’s like the Times read your question!)