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I was just reading about sailors testing positive after having already recovered from COVID-19. What’s going on?

Question: I was just reading about sailors on the USS Theodore Roosevelt testing positive again after having already recovered from COVID-19. What’s going on?

Answer: I read about that too! Cases like this have also been observed in Switzerland, South Korea, Japan, Italy, and China. We are still learning and don’t really have a solid answer on what’s going on. Here are three hypotheses as to what’s happening:

  • Hypothesis A: People are becoming infected for a second time (reinfection). This idea is considered by most scientists to be the least plausible because a) the timing between negative →positive is too short; b) patients don’t seem to have other sources of exposure; c) immunity should last in the short-term.
  • Hypothesis B: People are experiencing a reactivation of the virus. This idea is considered plausible. We discussed reactivation in our Q&A of 4/11. The basic idea is that the virus lays dormant for some time and then gets reactivated (perhaps due to stress or some other factor). One reason this holds water is that a number of the reactivated cases are folks who experience a second bout of illness symptoms. Many of the discussion sections of the papers I linked to above elaborate on this hypothesis and one scientist laid out some considerations in this recent Letter to the Editor. On the flip side, because SARS-CoV-2 does not infiltrate into the host cell’s nucleus (like hepB or HIV), the chances of it reactivating are very low.
  • Hypothesis C: Test results are false positives. This idea is also considered plausible; perhaps the most plausible given current data. The idea is that PCR tests identify RNA virus fragments, including fragments that are inactivated/dead. Because the tests do not differentiate between living/dead virus, they could be picking up the remnants of the virus in recovered patients. Indeed, the South Korea CDC reported at the end of April that dead virus fragments were the likely cause of 263 people testing positive again days and even weeks after marking full recoveries. In even better news, the South Korea CDC found zero transmission from such patients to others. This finding helps assuage concerns about the possibility of recovered individuals transmitting the virus to others — no evidence supports this!