As a journal Associate Editor and reviewer, I see lots of manuscripts about “new” viruses. I tend not to get too excited about most of them, because “new” is usually actually just “new to us” (or newly identified), because as technology improves, we are  able to identify lots of viruses that we’ve been living with for years. Viruses are part of our ecosystem, and most are harmless to us (and animals).

It’s common to find “new” viruses in sick people/animals, but they’re usually just background “noise,” because they can often be found just as frequently in healthy individuals. Differentiating something that’s “newly found but long present and harmless” from something that’s “been around and was an unknown cause of disease” from something that’s “truly a new emerging disease threat” is key (and sometimes easier said than done).

That brings me to a virus I wrote about in May: a “new” coronavirus that was found in 8 people in Malaysia who had pneumonia in 2017-2018. The virus was an alphacoronavirus that most closely resembled a canine coronavirus (notably SARS-CoV-2 and the common canine respiratory coronavirus are betacoronaviruses). The virus was named CCoV-HuPn-2018 (canine coronavirus-human pneumonia-isolated in 2018).  Whether these infections were a rare or one-off event wasn’t clear at the time.

However, a new study has reported finding this virus in a person in Florida who had returned from Haiti in 2017 (Lednicky et al. 2021). The person had pretty mild disease, but it was investigated and this same virus was found.

The fact that the person had only mild disease is important for context – very rarely do people with mild disease get tested, and even more rarely would a hunt for a new virus be performed in people with mild disease that had negative tests for the “usual suspects.” But they did test this person, and they once again found that the virus looks like it came from dogs (at some point), and it was found half a world away the same year.

This second report generates a lot of questions:

  • Was this another rare event, or does it represent a common, mild pathogen that’s circulating internationally?
  • Why were the cases in 2017 for both reports? Is this a virus that spread that year and burned out, or has there been limited study of it since then and it’s still with us (and we’re just not testing for it)?
  • What’s the role of dogs? There’s no information about the epidemiology of disease yet. Is it transmitted dog-to-human or did the dog-origin virus move into people and is now spread human-to-human?
  • Can this specific virus be found in dogs, or is this truly a human variant now?
  • Can the virus be spread back to dogs? If so, can it spread between dogs, can it cause disease in dogs, and can it be spread back to people?

These are all reasonable questions that could use more study. While this virus doesn’t seem like a big deal, it’s worth understanding more about the coronaviruses with which we live.  “Relax, but pay attention” is my typical response to new reports like these, and I think that’s fair here. The authors’ conclusion also fits with that:

Our data highlight the potential among coronaviruses for rapid evolution combined with frequent recombination events, leading to periodic emergence of strains capable of crossing species barriers into human populations. In many instances such strains would appear to be of low virulence for humans, as reflected in our work with PDCoV and now CCoV-Haiti; however, the potential for such strains to carry or acquire genes capable of causing severe disease in humans remains of clear concern.