Symptoms of Swine Flu (H1N1 Flu)

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Symptoms of swine flu, which is caused by the H1N1 virus, are like those of any seasonal flu and include fever, cough, runny nose, sore throat, body aches, chills, and fatigue. Although some people still talk about swine flu, it's important to keep in mind that now swine flu is considered another regular type of human flu virus, similar to other seasonal flu viruses.

In 2009, the big difference was that when the swine influenza A virus known as H1N1 first appeared, it was new and most people didn't have any immunity to it. That's why it so easily became a pandemic virus and spread all over the world. Now this strain is included in the annual flu vaccine.

h1n1 swine flu symptoms
Illustration by Verywell

Frequent Symptoms

Like other seasonal flu viruses, common symptoms of swine flu (H1N1) develop between one and three days after you've been infected and can include:

  • Fever, which is usually high, but is sometimes absent
  • Cough
  • Runny or stuffy nose
  • Sore throat
  • Body aches
  • Headache
  • Chills
  • Fatigue or tiredness, which can be extreme
  • Diarrhea and vomiting occasionally, but more commonly seen than with other strains of flu

The H1N1 strain is now included in seasonal influenza vaccines.

Serious Symptoms

Serious symptoms are rarer. In children, they can include:

  • Fast breathing or difficulty breathing
  • Bluish or gray skin color
  • Not drinking enough fluids
  • Severe or persistent vomiting
  • Not waking up or not interacting
  • Irritability so great that your child does not want to be held
  • Flu-like symptoms get better but then come back with fever and worse cough
  • Rash with a fever

In adults, serious symptoms include:

  • Difficulty breathing
  • Chest pain or pressure
  • Abdominal pain or pressure
  • Dizziness
  • Confusion
  • Vomiting that's severe or won't stop
  • Flu-like symptoms get better but then come back with fever and worse cough

If you notice these, don't panic right away. It's important to coordinate with a doctor or your medical team for prompt attention, and they can help you resolve the issue and its underlying cause.


Most people who get swine flu recover within a few days to two weeks after first having symptoms, but some people may develop complications.

H1N1 complications are most likely to occur if you:

  • are pregnant
  • are younger than 5 or older than 65 years old
  • have a chronic illness such as asthma, emphysema, diabetes, or heart disease

Potential complications include:

  • Worsening of a chronic condition
  • Pneumonia
  • Bronchitis
  • Ear infection
  • Confusion
  • Seizures
  • Respiratory failure

When to See a Doctor

Most normally healthy people can recover from the flu at home and prevent spreading it by avoiding other people. However, if you have a chronic illness like asthma, diabetes, or heart disease or have a suppressed immune system and you think you have the flu, you should see your doctor so he or she can properly diagnose you and treat your symptoms accordingly.

You may get a course of antiviral medications that are used for high-risk people to help lessen the length and severity of your illness.

H1N1 Swine Flu Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Man

You should seek emergency care if you or your child has any of the serious symptoms listed above and/or you're getting worse. This is especially true if you or your child has a chronic illness as well.

When to Seek Emergency Care for Infants

If your baby has the flu and the following symptoms occur, seek emergency care immediately.

  • Unable to eat
  • No tears when crying
  • Having difficulty breathing
  • Fewer wet diapers than normal

The flu can be a life-threatening disease for children, especially those 5 years of age and younger, people over 65, and those with chronic conditions, so getting medical care as soon as possible for these populations is important.

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