COVID-19 Can Feel A Lot Like the Stomach Flu, So How Can You Tell Them Apart?

Korin Miller
·5 min read
Photo credit: PeopleImages - Getty Images
Photo credit: PeopleImages - Getty Images

From Prevention

In pre-pandemic times, suddenly running to the bathroom due to diarrhea or vomiting would be a tip-off that you might have food poisoning or the stomach flu. But given that COVID-19 can present with various stomach-related symptoms, it might be trickier to understand what you’re dealing with—and what you’re supposed to do next.

It’s important to remember that a stomach flu isn’t the same as influenza, which is responsible for the typical “flu” as you know it—fever, achy muscles, sore throat, and generally feeling crummy. Instead, it’s a term usually used for gastroenteritis, a condition that is characterized by inflammation of the stomach or intestines, per the Centers for Disease Control and Prevention (CDC).

There are various causes behind a stomach flu, but one of the most common is norovirus, which can make a person incredibly ill between 12 and 48 hours after being exposed, the CDC says. In the U.S., norovirus causes up to 21 million cases of viral gastroenteritis every year.

While they can cause similar symptoms, norovirus and the novel coronavirus responsible for COVID-19 often spread differently. For example, you can develop norovirus after coming into contact with particles from an infected person’s poop or vomit, breathing in vomit aerosols, or eating contaminated food or water, while most people develop COVID-19 from inhaling respiratory droplets from an infected person they had close contact with.

So how can you differentiate a case of the coronavirus from the stomach flu? The symptoms can overlap, but they also have some differences. Here’s what doctors want you to know.

What are the symptoms of the stomach flu?

The symptoms can vary slightly, depending on what causes your stomach flu. In general, the CDC says you may experience the following symptoms, and start to feeling better within one to three days:

  • Diarrhea

  • Vomiting

  • Nausea

  • Stomach pain

  • Fever

  • Headache

  • Body aches

What are the symptoms of COVID-19?

The following are the major symptoms of COVID-19, according to the CDC, which “does not include all possible symptoms.” Many people who contract the novel coronavirus tend to feel ill for about two weeks.

  • Fever or chills

  • Cough

  • Shortness of breath or difficulty breathing

  • Fatigue

  • Muscle or body aches

  • Headache

  • New loss of taste or smell

  • Sore throat

  • Congestion or runny nose

  • Nausea or vomiting

  • Diarrhea

How to tell the difference between stomach flu and COVID-19

Unfortunately, this isn’t an easy thing to figure out—even for doctors, says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security.

“I don’t think it is possible to differentiate COVID-19 from other viral illnesses in the midst of the pandemic on clinical symptoms alone,” adds Richard Watkins, M.D., an infectious disease physician and a professor of internal medicine at the Northeast Ohio Medical University.

The problem is, some people with COVID-19 just have gastrointestinal symptoms, Dr. Watkins adds. “Diarrhea is one of the most common symptoms we see,” he says. “Sometimes people have no respiratory symptoms.”

One study found that, of 117 people with a confirmed case of COVID-19 experiencing GI symptoms, about 20% experienced diarrhea as their first symptom, and it lasted anywhere between one and 14 days. “Concurrent fever was found in 62.4% of patients with a digestive symptom,” the authors wrote.

But there is one major tip-off that you may be dealing with coronavirus instead of the stomach flu: developing a sudden loss of taste or smell. This symptom can occur with any viral illness, but seems to be much more common with COVID-19, says Lewis Nelson, M.D., chair of the Department of Emergency Medicine at Rutgers New Jersey Medical School. That, paired with other symptoms that aren’t as common with the stomach flu—such as a dry cough, sore throat, or runny nose—could be a sign that you’re dealing with coronavirus.

What’s more, a typical case of stomach flu tends to be short-lived—most people feel better in three days or less, per the CDC.

What should you do if you have stomach flu or COVID-19 symptoms?

Given how widespread and highly contagious COVID-19 is, Dr. Adalja says it’s a good idea to assume you may have a case of coronavirus and act accordingly. Isolate at home, call your doctor to ask about getting tested, and wear a face mask if you need to come into contact with others (which you should already be doing anyway).

Like COVID-19, there is no specific treatment for norovirus. Since both the stomach flu and gastrointestinal symptoms of COVID-19 can lead to dehydration due to diarrhea, it’s important to drink plenty of liquids until you start to feel better. Get plenty of rest, use fever-reducing medication like Tylenol if needed, and call your doctor ASAP if your symptoms start to get worse.

When you start to feel better, Dr. Adalja says it’s a good idea to continue with bland foods (think: soup, toast, oatmeal) and ease back into your normal diet slowly—otherwise you could risk upsetting your stomach again.

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