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Updated 14th March 2022

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Is my upset stomach a symptom of Omicron?

Written byTim Spector, MD FRCP FRSB
Reviewed byYella Hewings-Martin, PhD

    If you’ve had an upset tummy lately, you’re not alone. We’ve noticed a recent rise in people reporting gastrointestinal symptoms in the ZOE COVID Study app through January 2022.

    But is this due to the Omicron COVID variant? Or is there something else going on? Here’s what we know so far. 

    Is an upset stomach a sign of COVID-19?

    Thanks to millions of daily health reports from our dedicated ZOE COVID Study app contributors, we’ve shown from the earliest days of the pandemic that gastrointestinal (GI) problems — such as diarrhea, stomach pains, feeling sick and losing your appetite or skipping meals — can all be symptoms of COVID-19.

    Back in April 2020, we were also able to show that these kinds of symptoms tended to cluster together, forming one of six distinct "types" of COVID-19.

    We’ve recently spotted a sharp increase in the number of people reporting GI symptoms in the app from mid-December 2021 through January 2022. 

    Interestingly, this follows roughly the same pattern that we saw during the winter wave a year ago. The blue line in the chart below shows the proportion of people reporting GI symptoms in the app this year, while the orange line is from the same time last year.

    GI symptoms reported in the ZOE COVID app

    Is Omicron causing more gastrointestinal symptoms?

    Throughout the past 2 years, we’ve seen changes in the patterns of symptoms reported in the app as new variants have emerged and as more of the population have had one, two, three, or even four doses of the vaccine.

    GI symptoms were a common hallmark of COVID-19 earlier on in the pandemic with the original version of the virus, as well as the Alpha and Delta variants.

    So, we were curious to know whether the increase we’re seeing now was linked to the recent rise of the Omicron variant. 

    However, when we looked at PCR test results reported in the app, we made an interesting observation. While a significant proportion of people reporting GI symptoms tested positive, we also saw an increase in the proportion of people with these symptoms who tested negative.

    And there was a similar pattern with lateral flow test results.

    GI symptoms relative to COVID tests

    This suggests that even though Omicron can be associated with GI symptoms, the rates are not higher than what we saw with Delta. One or more other types of tummy bug are likely going around in the population at the current time.

    For example, norovirus is very common at this time of year — hence its nickname, the winter vomiting bug — but we do not currently have a way of testing whether people reporting GI symptoms in the app are infected with it. 

    How to avoid an upset stomach

    After 2 years of singing "Happy Birthday" in the bathroom and slathering on hand sanitizer, we now know that washing your hands isn’t always so relevant for avoiding COVID-19. 

    However, remembering to wash your hands after using the bathroom or being in other public or dirty environments will help to reduce your risk of catching a tummy bug.

    Similarly, good food hygiene practices — like washing your hands before cooking and eating, washing your hands after handling raw meat, and making sure that food is cooked properly — will help to protect against food poisoning. 

    We also know that there’s a strong connection between your health and your gut microbiome, which are the trillions of bacteria, fungi, protozoa, and other microbes living in your digestive tracts.

    Changing your diet can influence the range of microbes in the gut, and research shows that eating a diverse, plant-rich diet is associated with a healthier, more diverse microbiome, too.

    ZOE scientists and our colleagues run the largest nutritional study of its kind, and we've recently identified 15 “good” gut bugs that are linked to better health. We also found 15 “bad” bugs that are indicators of poor health. 

    You can take a quiz to find out how you can learn which “good” and “bad” microbes live in your gut, and which foods you should eat to help improve your gut health.

    Help us track the nation’s health

    These latest results show that the ZOE app is not only a powerful tool for studying COVID-19, but also for looking more broadly at the nation’s health.

    This is something we’ll be doing in more detail with our wider health studies, which we’re rolling out through the app over the coming months.

    The pandemic still isn’t over. We need as many people to keep logging daily health reports in the app to provide a picture of how COVID-19 is spreading in the U.K. and how the symptoms are changing in response to new variants and vaccines. 

    We’re also thrilled that more than 800,000 contributors have agreed to take part in further research to tackle some of the biggest health problems we face today, including heart disease, cancer, and dementia.

    Whether you just want to help us track COVID-19, or if you want to contribute to wider health science, download the ZOE app today and get involved in the future of health research. 

    Stay safe and keep logging.