24-Hour Flu: Experts on Symptoms, Treatment

When you feel under the weather and then unexpectedly rebound the next day, it’s understandable if you conclude you just went through the 24-hour flu. After all, this illness is known for being quick and intense.

But the 24-hour flu is a little bit of a vague concept, and it’s not technically a medical diagnosis. So enduring the illness can leave you feeling confused. Still, doctors say this is a real thing — it just can be caused by a variety of pathogens.

Given that plenty of illnesses tend to ramp up during the colder months, now is prime time for the 24-hour flu. Here’s what may be behind your fleeting health ordeal, plus how to ride it out as smoothly as possible.

Experts Featured in This Article:

Amesh Adalja, MD, is the senior scholar at the Johns Hopkins Center for Health Security.

Thomas Russo, MD, is a professor and chief of infectious disease at the University at Buffalo in New York.

What Is the 24-Hour Flu?

Again, the 24-hour flu isn’t a medical term, so your doctor would never diagnose you with this (or, at least, they wouldn’t write it in your chart). That said, the phrase could mean a few different things.

“People may use it colloquially to refer to a very short illness associated with malaise and upper respiratory symptoms, such as congestion and runny nose,” says infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security.

But the 24-hour flu could also be used to describe norovirus, says Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York. Norovirus is the leading cause of vomiting and diarrhea in the US, along with foodborne illness, according to the Centers for Disease Control and Prevention (CDC). It usually comes on hard and fast, and can be done in a day, Russo points out.

What About 24-Hour Fever and Chills?

There are a lot of things that can cause you to have a fever and chills for 24 hours, including COVID-19 and influenza, aka the actual flu, Dr. Russo says.

“If you have some level of immunity to a virus, from vaccination or a prior infection, your symptoms can be very short-lived,” Dr. Russo says. Everyone’s immune system also reacts to illnesses differently, he points out. That, coupled with the wide range of viruses swirling around out there, means you could simply have a shorter course of illness when you get sick.

What Is the Gastrointestinal Flu?

If you’re dealing with gastrointestinal symptoms like vomiting and diarrhea, including both at once, it’s likely that you have norovirus. “When people refer to the ‘stomach flu,’ it is almost always norovirus,” Dr. Adalja says.

While norovirus isn’t technically a flu, it’s still not fun. “People are pretty miserable with norovirus,” Dr. Russo says. “They think they are going to die in those 24 hours.”

Norovirus is incredibly contagious — it usually takes less than 100 norovirus particles to make you sick. People with the condition can shed billions of these particles, making it easy to catch if you’re around someone who is sick, Dr. Russo says.

24-Hour Flu Symptoms

Symptoms of the 24-hour flu largely depend on what’s behind your illness. If you’re dealing with a respiratory illness, doctors say you may have these symptoms:

But if your symptoms are more in the gastrointestinal arena, you might have these:

What Causes a 24-Hour Flu?

There are a lot of pathogens that can cause what’s labeled as the 24-hour flu. COVID-19, for example, is caused by SARS-CoV-2, the flu is caused by the influenza virus, and norovirus is caused by norovirus particles. But you can catch the 24-hour flu a few different ways.

For respiratory illnesses, the 24-hour flu is usually caused by coming into contact with someone who is infected. That may mean breathing in infected particles or touching a contaminated surface and then touching your eyes, nose, or mouth, Dr. Russo says.

But you can pick up a stomach bug like norovirus from having direct contact with someone who is sick, eating contaminated food or drinks, or touching contaminated objects and then putting your unwashed fingers in your mouth, according to the CDC. (Just a heads up: You can still spread norovirus for two weeks or more after you feel better.)

How to Treat the 24-Hour Flu

There’s no specific treatment or medication to take when you have the 24-hour flu, but there are a few things you can do to help you feel better while you’re dealing with it.

Regardless of whether you have gastrointestinal or respiratory symptoms, Dr. Russo says that rest and doing your best to keep up your fluid intake can be helpful. If you’re struggling with vomiting, taking small sips of liquids vs. larger gulps may help you to keep things down, he says.

But if your symptoms are mostly respiratory, Dr. Adalja says that over-the-counter cold and cough medications may help you feel more comfortable.

If you make it through the 24 hours and feel better, there’s no need to see a doctor. But if you’re still not feeling great over time or you start to feel worse, Dr. Russo says it’s a good idea to check in with a medical professional about next steps.

Korin Miller is a writer specializing in general wellness, health, and lifestyle trends. Her work has appeared in Women’s Health, Self, Health, Forbes, and more.