If you have ever come down with the stomach flu and have experienced bouts of crushing nausea, vomiting, and diarrhea, it is not uncommon to be consoled by someone who will assure you that it's just a "24-hour bug."

But is there really such a thing? Can a stomach bug actually slip through your system as fast as that, leaving behind only a vague memory of the illness?

Understanding Stomach Flu

When describing a stomach bug, the word "flu" is a bit of misnomer. In purely medical terms, the flu (influenza) is a common viral infection that primarily affects the respiratory system and manifests with symptoms such as fever, chills, muscle aches, cough, and congestion.

By contrast, the stomach flu is more accurately referred to as gastroenteritis. Unlike influenza, gastroenteritis can be caused by any number of disease-causing pathogens, including bacteria, viruses, parasites, and even fungi. It is commonly associated with the rotavirus in children and either the norovirus or the Campylobacter bacteria in adults. Here's a brief look at the main differences between stomach flu and seasonal flu.

Stomach Flu

Also known as gastroenteritis or infectious diarrhea
Gastrointestinal infection that can be caused by a virus, bacterium, or parasite
Spreads via person-to-person contact, contaminated food or water, or, in the case of parasites, contact with infected feces
Symptoms include vomiting, diarrhea, fever, and stomach pain
Vomiting usually lasts 24 hours; diarrhea may continue for several days

Flu

Also known as seasonal influenza
Upper respiratory infection caused by a virus
Spreads by dissemination of virus in droplets spewed into air when an infected person sneezes or coughs; particles can travel as far as six feet
Symptoms include fever, chills, muscle aches, cough, and congestion
May last from two to 10 days
Can be prevented with a yearly vaccine

Clearly, because the causes of stomach flu are varied, it may be overly optimistic to suggest that it will automatically resolve in 24 hours. It may do so, but it can also take up to 10 days for some to fully recover.

Stomach flu can last from 24 hours to over a week, depending on the type.

Symptoms

Gastroenteritis, also known as infectious diarrhea, is characterized by the inflammation of the stomach and gastrointestinal tract and can lead to vomiting, diarrhea, fever, and abdominal distress. In general stomach flu appears suddenly, hits hard, then gets better once the symptoms subside.

Causes

While many types of viral illnesses such as influenza and the common cold tend to be transmitted in the air, gastroenteritis tends to be transmitted contaminated food and water or from person-to-person by contact. Handwashing after using the restroom and strict attention to food preparation guidelines are both aimed at preventing this transmission.

The most common causes of stomach flu include:

Viruses such as rotavirus, norovirus, adenovirus, and astrovirus are known to cause viral gastroenteritis. These represent around 70% of stomach flu in children (most especially the rotavirus), while the norovirus represents around 60% of all cases in the United States. The viruses are extremely contagious and easily passed from person to person or indirectly through contaminated food and water.
Bacterial causes include Campylobacter jejuni, Escherichia coli, Salmonella, Shigella, and Clostridium difficile. Bacteria-associated gastroenteritis is primarily related to something you ate. Of the possible bacterial causes, Campylobacter strains account for around one-third of all cases. Many of these infections are transmitted through contaminated poultry or other tainted foods, including meat, produce, and dairy products.
Parasites are less common causes of gastroenteritis but still account for around 3% of all cases in children. The primary culprit is Giardia lamblia which is spread through contaminated food, water or by the fecal-oral route (poor hygiene).

Treatment

how to treat the stomach flu — Illustration by Emily Roberts, Verywell

Symptoms of gastroenteritis are usually acute and resolve on their own without the need for medical intervention. The main focus of treatment is the prevention of dehydration due to the severe loss of fluids. Supportive therapies may include:

Rehydration with water or electrolyte-rich sports drinks (although sodas and any fruit juice high in simple sugar should be avoided)
A BRAT diet (consisting of banana, rice, apple, and toast) to ease a queasy stomach and help bind loose tummies
Anti-nausea medicines like Reglan (metoclopramide) to reduce the incidence of vomiting and lessen the risk of dehydration
Tylenol (acetaminophen) to relieve fever with fewer side effects and less stomach upset

When to Call the Doctor

Call your doctor immediately or go to the emergency room if vomiting or diarrhea persists for more than 24 hours, if vomiting is violent (or there is blood in the vomit), if you can't keep fluids down, or if there are signs of severe dehydration (dizziness, weakness, confusion, fainting, fever over 101 F).