How H1N1 Swine Flu Is Diagnosed

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Diagnosing H1N1 swine flu is typically done through a combination of lab testing and clinical diagnosis by your healthcare provider. Doing a physical exam and asking thorough questions about your symptoms and illness are also important.

Determining what is making you sick is not as easy as it might seem. Most people who are diagnosed with H1N1 are told that this is what they have because of their symptoms, a lab test that is positive for influenza A, and the knowledge that the dominant strain causing illness in the community at that time is H1N1. It's rare that more definitive diagnosis is done through laboratory testing.

When the outbreak and pandemic began in 2009, testing was more difficult because the strain of influenza was new to humans. However, since that time, the H1N1 strain of influenza that caused the pandemic has been tracked and frequently identified.

h1n1 swine flu diagnosis
Illustration by Verywell

Self-Checks/At-Home Testing

There are no home testing kits that are accurate or approved for any type of influenza, including H1N1 swine flu.

It is important to know the symptoms of H1N1 swine flu so that you will know if you need to see your healthcare provider to be tested. Although the symptoms are similar to those of many other upper respiratory viruses, the flu is typically more severe and its onset is sudden. Unlike a cold, which comes on gradually over a few days, the flu hits you all at once with severe symptoms like fatigue, fever, and muscle aches.

Labs and Tests

If you think you might have the flu, see your healthcare provider within the first 48 hours of the start of your symptoms. If you need treatment with antiviral medicine, it will be the most effective if it is started early in the illness.

If your healthcare provider examines you and thinks you might have H1N1 swine flu, there are a few tests he might use to diagnose you. The most common is a rapid flu test. This consists of a nasal or throat swab that provides rapid results in the office in under 20 minutes. Depending on the test, you may either be told that you simply do or do not have the flu (influenza), or you do or do not have influenza A or B.

H1N1 swine flu is a type of influenza A but rapid flu tests that are performed in the office cannot determine typing, so you won't know for sure what strain of influenza is making you sick. If there is a certain strain that is causing illness in your community and you test positive, chances are good that you have that type also.

Specialty labs around the country and the CDC do perform analysis of influenza throughout the year to determine which strains are making people sick. In rare cases, your test may be sent to one of these labs for typing and you or your healthcare provider may find out exactly which strain of influenza you have. This more commonly occurs in people that are hospitalized, but is not routine.

Differential Diagnosis

There are many viruses and illnesses that can cause flu-like symptoms. Just because you think you have the flu—or even if your healthcare provider thinks you do—doesn't mean your symptoms are actually caused by influenza. There are hundreds of known viruses that cause upper respiratory symptoms and likely many more that we don't know about yet.

Common illnesses that are often mistaken for influenza include:

  • The common cold
  • Parainfluenza
  • Gastroenteritis (stomach flu)
  • Pneumonia (this is a common complication of the flu but may be missed initially)

If you aren't sure what is making you sick or if you are concerned that your symptoms have become more severe, contact your healthcare provider. Influenza often leads to other illnesses such as bronchitis, ear infections, and pneumonia. Many of these need to be treated differently than the initial flu. Be sure you are getting the correct treatment by talking to your healthcare provider whenever you have questions.

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