How do you know if you have swine flu or seasonal flu?

The Differences Between Seasonal Flu and Swine Flu

A pregnant woman with swine flu symptoms receiving medical treatment in Argentina.
A pregnant woman with swine flu symptoms receiving medical treatment in Argentina.
Associated Press/Pablo Barrera

Some people already have enough trouble determining if they have a cold or a flu; the symptoms are similar, although the flu's symptoms are a bit more intense. But it may be especially difficult to know if you have swine flu or seasonal flu, as the symptoms are, again, extremely similar. Symptoms include fever, cough, sore throat, stuffy or runny nose, body aches, headache, chills and fatigue. Swine flu patients also report diarrhea and vomiting, not usually present in seasonal flu.

A laboratory test is the only way to confirm a case of swine flu, but few tests have been done as most swine flu cases thus far look like a bout with seasonal flu. Many people recover without needing any medication or hospitalization, and some might not even know they're ill. The mild nature of swine flu has led some to question why there needs to be any worry, as deaths have been far less than those attributable to seasonal flu. In the United States alone, one flu season can require 200,000 hospitalizations and cause 36,000 deaths [source: CDC]. The seasonal flu can be especially dangerous for infants, the elderly and people with weakened immune systems.

However, because the current H1N1 influenza is completely new and no one has immunity, public health officials warn that swine flu could eventually cause more complications than seasonal flu does. Not only will there be more complications, they'll likely be more serious. So far, doctors have reported that swine flu is more likely to result in viral pneumonia, as opposed to bacterial pneumonia often seen in seasonal flu cases; the bacterial version is much easier to treat than the viral kind.

Recent work with ferrets, who experience flu much the same way humans do, suggests why the complications from swine flu might be so much worse. In 2009, researchers found that the seasonal flu virus binds itself to ferrets' noses, but that swine flu went deeper, binding itself to the trachea, bronchi and bronchioles in the lungs [source: Reinberg]. The virus even made its way to the ferrets' intestines, which may explain the diarrhea and vomiting that distinguish swine flu. The H1N1 virus replicated much more often in the ferrets, too, causing more extensive damage.

Even if you don't know if you have swine flu or seasonal flu, head to the doctor if you start to experience symptoms that aren't part of a typical flu experience; these may be the warning signs of serious swine flu complications. Pregnant women and adults aged 5 to 24 are thought to be at higher risk of swine flu complications, so be particularly alert if you fall into those groups. On the other hand, seasonal flu complications usually affect the elderly and children under 5. That means everyone needs to remain vigilant about their health in the coming months.

Because swine flu and seasonal flu are transmitted in the same way, everyone can be on watch when it comes to prevention. Cover your mouth when you cough or sneeze, wash your hands often and stay home when you're sick. Whether you have seasonal or swine flu, you'll be doing everyone around you a favor.

Related HowStuffWorks Articles

More Cold and Flu Questions


  • Beam, Christopher. "Swine Flu FAQ." Slate. May 1, 2009. (Aug. 3, 2009)
  • Centers for Disease Control and Prevention. "Novel H1N1 Flu (Swine Flu)." (Aug. 3, 2009)
  • Davey, Monica. "Thousands Face a Balancing Act Over Flu Fears." New York Times. May 1, 2009. (Aug. 3, 2009)
  • DeNoon, Daniel J. "Pregnany Raises Swine Flu Death Risk." WebMD. July 29, 2009. (Aug. 3, 2009)
  • DeNoon, Daniel J. "Swine Flu Pandemic FAQ." WebMD. (Aug. 3, 2009)
  • DeNoon, Daniel J. "Swine Flu FAQ." WebMD. (Aug. 3, 2009)
  • DeNoon, Daniel J. "WHO Declares Swine Flu Pandemic." June 11, 2009. (Aug. 3, 2009)
  • Di Justo, Patrick. "The Last Great Swine Flu Epidemic." Salon. April 28, 2009. (Aug. 3, 2009)
  • "Flu Special Report: The Basics." LiveScience. April 26, 2009. (Aug. 3, 2009)
  • Grady, Denise. "Swine Flu Plan Would Put Some Ahead for Vaccine." New York Times. July 30, 2009. (Aug. 3, 2009)
  • "H1N1 Flu Virus (Swine Flu)." WebMD. (Aug. 3, 2009)
  • Hitti, Miranda. "Putting Swine Flu in Perspective." WebMD. May 1, 2009. (Aug. 3, 2009)
  • MacKenzie, Debora. "Revealed: How pandemic swine flu kills." New Scientist. July 3, 2009. (Aug. 3, 2009)
  • McNeil, Donald G., Jr. "Swine Flu Expected to Return With Opening of School." New York Times. July 18, 2009. (Aug. 3, 2009)
  • McNeil, Donald G., Jr. "U.S. Declares Public Health Emergency Over Swine Flu." New York Times. April 27, 2009. (Aug. 3, 2009)
  • Reinberg, Steven. "Why Swine Flu Differs from Seasonal Flu." HealthDay. July 2, 2009. (Aug. 3, 2009)
  • Stobbe, Mike. "Swine Flu Could Hit 40 Percent in United States." Time. July 25, 2009. (Aug. 3, 2009),8599,1912816,00.html
  • "Swine Flu (H1N1 Flu)." Mayo Clinic. July 31, 2009. (Aug. 3, 2009)
  • "Swine Flu More Severe than Seasonal Flu." LiveScience. July 14, 2009. (Aug. 3, 2009)
  • Walsh, Bryan. "Think H1N1 is Bad Now? Wait Till Flu Season." Time. July 22, 2009. (Aug. 3, 2009),8599,1912087,00.html
  • Walsh, Bryan. "Top 5 Swine Flu Don'ts." Time. May 1, 2009. (Aug. 3, 2009),8599,1895216,00.html
  • World Health Organization. "Pandemic (H1N1) 2009." (Aug. 3, 2009)