Does Influenza Cause Stomach Flu?

A stomach flu is often mistaken for influenza, a type of virus for which one might receive a yearly flu shot to prevent. Often, people believe they could have prevented the stomach flu by getting a yearly flu shot, but this is not the case. Stomach flu is caused by viruses, or sometimes ingestion of bacterial agents, and is never caused by what most people call “the flu.”

Influenza tends to involve fever, aches, sore throat, nasal and chest congestion. In both the very young and the elderly, the flu can result in complications like pneumonia. It is recommended that children under the age of five receive a flu shot. As well, senior citizens should also receive the shot. People with compromised immune systems, their caregivers and those in the medical community should also get the yearly vaccination.

These vaccinations can help to prevent the types of flu viruses expected each year. They do not always work. Scientists must develop vaccines based on viruses they predict will be present in a given year. A noted failure occurred in 2004, with the vaccine failing to protect against the prevalent viruses that year.

In all cases, however, the influenza vaccine has very little effect on preventing the stomach flu. This is often misunderstood since both stomach bugs and influenza are referred to as the flu. The typical stomach flu lasts for about two to three days, may cause fever, and may result in vomiting, diarrhea or both.

Often stomach flu is in fact mild food poisoning. Most agents responsible for food poisoning are bacterial. Particularly prevalent is salmonella, which in the healthy person can manifest as stomach flu type symptoms within a few hours to a day after eating contaminated food. Often, in healthy people, salmonella poisoning resolves without treatment. Rest and fluids are encouraged.

Bacterial or parasitic agents that are more severe will be noted if the person is running a very high fever and cannot keep any fluids down. If this is the case, the person should see a doctor immediately. Stronger bacteria or parasites may cause extreme dehydration and in some cases kidney failure. This type of stomach flu usually requires medication to cure the illness. The very young and the elderly are especially at risk of developing complications due to bacteria like E. coli and listeria.

Viruses causing the stomach flu are generally called noroviruses. These can be mild, affecting a person for a day or two. In young children, noroviruses may linger and a child who seems to have recovered from the stomach flu may exhibit symptoms a few days later. Usually noroviruses will last 24-48 hours. If vomiting or diarrhea continues beyond this point, one should see a doctor, as the cause may be food poisoning, or simply a stubborn virus.

Again, the elderly and young children are most vulnerable to complications and are more likely to suffer dehydration from noroviruses. If a person cannot keep liquids down after the first day, a doctor should be consulted. Some require intravenous (IV) fluids to help rehydrate the body and restore health.