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 days after infection.

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

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.

The most common symptoms of the flu are:

  • fever over 100.4˚F (38˚C)
  • chills
  • fatigue
  • body and muscle aches
  • loss of appetite
  • headache
  • 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.

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:

  • worsen
  • 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), 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
  • 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, 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 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.

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.

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:

  • water
  • 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:

The U.S. Food and Drug Administration (FDA) 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.

Ask your doctor about taking over-the-counter medications for pain and fever relief, such as ibuprofen (Advil) or acetaminophen (Tylenol).

The best way to avoid flu symptoms is to prevent the spread of the virus in the first place. Anyone 6 months of age and older should get an annual flu vaccination.

Flu shots are also recommended for pregnant women. While not completely foolproof, the flu vaccine can significantly decrease your risk for catching the flu.

You can also prevent getting and spreading the flu by:

  • avoiding contact with others who are sick
  • staying away from crowds, especially at peak flu season
  • washing your hands frequently
  • avoid touching your mouth and face, or eating foods before washing your hands
  • covering your nose and mouth with your sleeve or a tissue if you need to sneeze or cough

It can take up to two weeks for flu symptoms to completely go away, though the worst of your flu symptoms usually begin subsiding after a few days. Talk to your doctor if flu symptoms last longer than two weeks, or if they disappear and then reappear worse than before.