What is the flu?
The flu’s common symptoms of fever, body aches, and fatigue can leave many confined to bed until they get better. Flu symptoms will show up anywhere from one to four daysTrusted Source after infection.

They often appear suddenly and can be quite severe. Luckily, symptoms generally go away within one to two weeksTrusted Source.

In some people, especially those at high risk, the flu may lead to complications that are more serious. Inflammation in the small lung airways with infection, known as pneumonia, is a serious flu-related complication. Pneumonia can be life threatening in high-risk individuals or if left untreated.

Common flu symptoms
The most common symptoms of the flu are:

fever over 100.4˚F (38˚C)
body and muscle aches
loss of appetite
dry cough
sore throat
runny or stuffy nose
While most symptoms will taper off one to two weeks after onset, a dry cough and general fatigue can last several more weeks.

Other possible symptoms of the flu include dizziness, sneezing, and wheezing. Nausea and vomiting are not common symptoms in adults, but they sometimes occur in children.

Emergency flu symptoms
Individuals at high risk for flu complications include those who:

are under 5 years old (especially those younger than 2 years old)
are 18 years old or younger and taking medications containing aspirin or salicylate
are 65 years old or older
are pregnant or up to two weeks postpartum
have a body mass index (BMI) of at least 40
have Native American (American Indian or Alaska Native) ancestry
live in nursing homes or chronic care facilities
People who have weakened immune systems due to health conditions or the use of certain medications are also at a high risk.

People at high risk for flu complications should contact their doctor if they experience any flu symptoms at all. This is especially true if you have a chronic health condition like diabetes or COPD.

Older adults and those with compromised immune systems might experience:

breathing difficulties
bluish skin
severely sore throat
high fever
extreme fatigue
Severe symptoms

You should contact your doctor as soon as possible if flu symptoms:

last more than two weeks
cause you worry or concern
include a painful earache or fever over 103˚F (39.4˚C)
When adults should seek emergency care

According to the Centers for Disease Control and Prevention (CDC)Trusted Source, adults should seek immediate emergency treatment if they experience any of the following symptoms:

difficulty breathing or shortness of breath
chest or abdomen pain or pressure
dizziness that is sudden or severe
vomiting that is severe or constant
symptoms that disappear and then reappear with a worsened cough and fever
When to seek emergency care for infants and children

According to the CDCTrusted Source, you should seek medical care immediately if your infant or child has any of the following symptoms:

irregular breathing, such as difficulties breathing or rapid breathing
blue tint to skin
not drinking an adequate amount of fluids
difficulty waking up, listlessness
crying that gets worse when the child is picked up
no tears when crying
flu symptoms that disappear but then reappear with a fever and a worsened cough
fever with a rash
loss of appetite or an inability to eat
decreased amount of wet diapers
Pneumonia symptoms
Pneumonia is a common complication of the flu. This is especially true for certain high-risk groups, including people over 65, young children, and people with already weakened immune systems.

Visit an emergency room immediately if you have symptoms of pneumonia, including:

a severe cough with large amounts of phlegm
difficulty breathing or shortness of breath
fever higher than 102˚F (39˚C) that persists, especially if accompanied by chills or sweating
acute chest pains
severe chills or sweating
Untreated pneumonia can lead to serious complications and even death. This is especially true in older adults, tobacco smokers, and people with weakened immune systems. Pneumonia is particularly threatening to people with chronic heart or lung conditions.

Stomach flu
An illness commonly known as the “stomach flu” refers to viral gastroenteritis (GE), which involves inflammation of the stomach lining. However, stomach flu is caused by viruses other than influenza viruses, so the flu vaccine will not prevent stomach flu.

In general, gastroenteritis can be caused by a number of pathogens, including viruses, bacteria, and parasites, as well as noninfectious causes.

Common symptoms of viral GE include mild fever, nausea, vomiting, and diarrhea. On the other hand, the influenza virus doesn’t typically cause nausea or diarrhea, except sometimes in small children.

It’s important to know the difference between the symptoms of regular flu and the stomach flu so you can get proper treatment.

Young children, the elderly, and those with poor immune system function are at higher risk for complications related to untreated viral GE. These complications can include severe dehydration and sometimes death.


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Treating the flu
Unlike bacterial infections, the influenza virus is best treated with bedrest. Most people feel better after a few days. Fluids, such as the following, are also helpful in treating symptoms of the flu:

herbal tea
brothy soups
natural fruit juices
In some cases, your doctor might prescribe an antiviral medication. Antiviral drugs don’t get rid of the flu entirely, as they do not kill the virus, but they may shorten the course of the virus. The medications may also help prevent complications such as pneumonia.

Common antiviral prescriptions include:

zanamivir (Relenza)
oseltamivir (Tamiflu)
peramivir (Rapivab)
The U.S. Food and Drug Administration (FDA)Trusted Source also approved a new medication called baloxavir marboxil (Xofluza) in October of 2018.

Antiviral medications must be taken within 48 hours of the onset of symptoms in order to be effective. If they’re taken during this time period, they can help shorten the length of the flu.

Prescription medications for the flu are generally offered to those who may be at risk for complications. These drugs can carry the risk of side effects, such as nausea, delirium, and seizures.