COVID or gastrointestinal illness? Why it's hard to know right now

If you've felt green around the gills recently, or heard more tales than usual about stomach upsets, you might have wondered if Omicron or its subvariant, BA.2, are causing an increase in gastrointestinal issues.

Some clinicians have also reported seeing more COVID-19 patients suffering from GI symptoms in recent weeks. 

But medical experts say there are a few possible explanations — and it's not necessarily due to the COVID-19 strains currently circulating in Canada. Diarrhea, vomiting and abdominal pain have been recognized as common symptoms of COVID-19 since early in the pandemic, while nausea, reflux, heartburn, loss of appetite and weight loss are also recognized as potential symptoms.

Dr. Sumon Chakrabarti, an infectious diseases specialist in Mississauga, Ont., said he's recently seen a higher proportion of COVID-19 patients whose primary symptoms are gastrointestinal. 

"I've seen people that just present with vomiting," he said. 

But, he adds, it's not that Omicron is necessarily causing more GI issues, but rather, that it's now easier to detect COVID-19 in those patients than it was earlier in the pandemic.

"We're testing people that are coming in sick enough to be admitted, and also, people are doing rapid tests at home with any kind of symptom, so it also could be a possibility that we're just picking these up because we're looking for them."

Chakrabarti's hypothesis is backed up by data from the U.K.-based ZOE COVID Symptom Study App, through which millions of people have reported their symptoms during the pandemic. 

Based on those user reports, there's no evidence of Omicron causing an upsurge in gastrointestinal symptoms, said lead researcher Tim Spector, a professor of genetic epidemiology at King's College London.

"It seems to be fairly stable. We're not seeing major shifts in the symptoms. It's still very much an upper respiratory infection," he told CBC News.

However, some pediatricians say they have seen a definite uptick in COVID-19 patients with gastrointestinal symptoms during the Omicron wave — and some of those symptoms are especially concerning.

Dr. Ana Sant'Anna, a pediatric gastroenterologist at the Montreal Children's Hospital, said she has recently seen young patients with blood in their stool or vomit, and some had suffered tears in their gastrointestinal tract as a result of their vomiting.

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"We didn't see these [symptoms] before," Sant'Anna said, adding that none of those patients with serious GI symptoms had any respiratory symptoms during their time in hospital.