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.

Pediatricians seeing concerning symptoms in kids

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.

Despite the severity of their symptoms, nearly all the young COVID patients bounced back quickly after treatment, she said.

"They resolve in a few days, maybe a couple weeks, and they go [out] as good as new."

Other gastro infections on the rise

Aside from COVID-19, there's another reason why more Canadians might be experiencing some unpleasant intestinal symptoms right now.

Stomach bugs, like norovirus, are increasingly circulating as life returns to normal, Chakrabarti said, with children often becoming infected with gastro-type illnesses at school, then infecting their families.

Norovirus symptoms can include diarrhea, vomiting, nausea and stomach cramps.

Recent clusters of that illness in New Brunswick affected schools, child-care centres, and long-term care homes, while hundreds of people in B.C., Alberta, Saskatchewan and Ontario fell ill after eating raw oysters.

Children are especially at risk of dehydration from diarrhea and vomiting, whether from COVID-19 or another gastro illness, and should be monitored closely for signs such as less urination, Sant'Anna said.

It's important to keep them hydrated, and over-the-counter medications may help control vomiting. However, if children cannot keep liquids down due to continued vomiting, they may need hospital treatment with intravenous fluids, she said.

And — as is well known at this stage of the pandemic — hand-washing is an important precaution for preventing the spread of illness.

Can COVID-19 cause long-term gut damage?

There is limited but growing evidence of people experiencing lasting gastrointestinal issues, months after a COVID-19 infection, including indigestion and post-infectious irritable bowel syndrome (IBS).

A recent pre-print study by American researchers, which has not yet been peer-reviewed, hypothesized that the virus might disrupt gut bacteria, and potentially contribute to long COVID.

Other infections, including viruses, bacteria and parasites, can disrupt gut motility — the contractions of muscles to push food through the digestive tract — which can lead to IBS and other conditions.

Dr. Gil Kaplan, a gastroenterologist and epidemiologist at the University of Calgary, said it's also possible some people may have had existing, but undiagnosed, GI issues, which were exacerbated by COVID-19.

He is part of a team researching the impact of COVID-19 on people living with Crohn's disease and ulcerative colitis, collectively known as inflammatory bowel diseases.

"It's not surprising to me that we're starting to see things like irritable bowel and other types of conditions linked to COVID, that have probably been linked to other infections in the past, but we just haven't studied [those infections] as extensively as we have with COVID," Kaplan said.

It's important that people experiencing ongoing gastro symptoms speak to a doctor for diagnosis and treatment, he said.

For now, kids don't appear to be suffering longer-term GI issues as a result of their COVID-19 infections, Sant'Anna said — although that could change in future.

"It could be that we will see this a little bit later than the adults, because in terms of the timing, the kids are just now having this, so we [haven't had] time to have the post-IBS symptoms."