Recognizing Flu Symptoms

Written by the Healthline Editorial Team | Published on October 20, 2014
Medically Reviewed by Brenda B. Spriggs, MD, MPH, MBA on October 20, 2014

Symptoms of the Flu

Nobody likes to get the flu. The flu’s common symptoms of fever, body aches, and fatigue can leave many confined to bed rest until symptoms subside. Flu symptoms will show up anywhere from one to four days after infection. They often appear suddenly and can be quite severe. Luckily, symptoms generally subside within one to two weeks.

There are two situations that could cause concern. Talk to your doctor if flu symptoms last longer than two weeks, or if they disappear and then reappear with worsened symptoms.

In some individuals, especially those at high risk, the flu may develop into complications that are more serious. Lung inflammation (pneumonia) is the most common flu-related complication. Pneumonia can be life threatening in high-risk individuals or if left untreated.

Individuals at high risk for flu complications include those:

  • under 5
  • who are pregnant
  • 65 and over

People who have weakened immune symptoms due to health conditions or the use of certain medications are also at a high risk.

Common Flu Symptoms

The most common symptoms of the flu are:

  • fever (over 100 F)
  • chills
  • fatigue
  • body and muscle aches 
  • loss of appetite
  • headache
  • dry cough
  • sore throat
  • 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

When to Contact Your Doctor

Contact your doctor as soon as possible if flu symptoms:

  • worsen
  • last more than two weeks
  • cause you worry or concern
  • include a painful earache or fever over 103 F
  • include a severe cough with a large amount of mucus, difficulty breathing, chest pain, and/or a prolonged fever over 102 F with chills or sweating (symptoms of pneumonia) 

People at high risk for flu complications should also 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.

When Adults Should Seek Emergency Care

According to the Centers for Disease Control and Prevention (CDC), 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
  • fainting
  • mental confusion
  • 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 CDC, seek medical care immediately if your infant or child has any of the following symptoms:

  • problems breathing (including 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. You should 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 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, 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” is actually a form of gastroenteritis (GE).  GE is an irritation of the stomach lining. The disease can be caused by any number of pathogens, including viruses, bacteria, and parasites.

Common symptoms include mild fever, nausea, and diarrhea. The influenza virus doesn’t typically cause nausea or diarrhea, except sometimes in small children. It’s important to distinguish between the symptoms of regular flu and the stomach flu so you can get proper treatment. 

Young children are at higher risk for complications related to untreated GE. These complications can include severe dehydration and sometimes death. 

Read about other causes of dizziness and wheezing

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