Influenza (flu) can be a serious and sometimes life-threatening respiratory illness caused by influenza viruses. The Centers for Disease Control and Prevention estimates that since 2010, flu has caused between 140,000 and 960,000 hospitalizations and between 12,000 and 79,000 deaths each year. The best way to help prevent the flu is by getting vaccinated every year, as vaccinations have been shown to reduce the risk of flu illness. However, if you do get sick, you’ll want to determine if it’s caused by a flu virus so you can quickly start treatment if needed.

Wisconsin Diagnostic Laboratories (WDL), the largest Wisconsin-based laboratory and provider to the Froedtert & the Medical College of Wisconsin health network, can help with that determination. WDL exclusively uses rapid and highly sensitive Nucleic Acid Amplified Testing (NAAT), which extracts influenza viral ribonucleic acid (RNA) from your nasal swab sample and multiplies it using a technique called reverse transcription-polymerase chain reaction. This technique rapidly produces billions of copies of your RNA, greatly increasing the test’s ability to detect a flu virus. Providing you with an accurate result within 30 minutes, this test is the quickest way to know if you should start antiviral treatment, which works best against a flu virus if started sooner rather than later. Below, find additional information on the flu, as well as alternative flu tests to be aware of.

Why am I feeling so bad?

Flu is contagious and can make you feel bad soon after you “catch” the virus. The virus gets into cells in the respiratory tract where it reproduces rapidly, causing symptoms such as fever, chills, body aches, headache, fatigue, cough and sore throat. Some of these symptoms are similar to the common cold, but are usually more severe.

The Flu Virus Family

There are three major types of influenza virus: Types A, B and C. Types A and B are more commonly seen in humans. Type C rarely causes human infections. Influenza viruses are constantly changing or mutating. These mutations can eventually lead to different subtypes, especially in influenza A. These constant changes are the reason it is important to be vaccinated every year. The mutations are also the reason the vaccines are not quite as effective some years – creating an ongoing battle between researchers and the virus.

Suboptimal Flu Virus Tests

Because other respiratory illnesses can mimic flu, it is important to test for the flu virus. To test for flu, a respiratory sample is obtained using a thin, flexible swab that is inserted through the nostril and eased down into the back of the nasopharynx, where the highest concentration of virus exists.

Accurate and rapid testing, like the NAAT used within the Froedtert & MCW health network, helps determine the best treatment choices. As previously mentioned, if antiviral treatment is indicated, the sooner it is given, the better the outcome. It’s important to be aware of other flu tests that are not as quick or accurate as the NAAT:

  • Rapid Shell Vial and Viral Tissue Cell Culture Tests – These tests involve growing the virus in tissue culture tubes. While the virus reproduces rapidly, rapid cell culture results usually take 1–3 days, while viral tissue cell culture takes 3–10 days. Either way, the results are usually too late to treat the patient.
  • Rapid Influenza Antigen Tests – The proteins on the surface of the influenza virus are called antigens. These antigens produce an immune (antibody) response by your body. This class of tests detects flu virus antigens. These are rapid tests, but are not highly sensitive, leading to the possibility of a false-negative result.

Even though these other tests are not as fast and sensitive as NAAT, they are still important to help track the strains that are circulating during the flu season. This information is useful for developing overall strategies to help prevent epidemics and to help predict seasonal strains for optimal vaccines.

Whether you share home space with young children, share an office space or take care of aging adults, minimizing the impact of the flu is a goal we all share. In addition, WDL and the Froedtert & MCW health network share a goal to make you feel better fast this season, and flu NAAT can help you achieve that goal.

Wisconsin Diagnostic Laboratories (WDL) specializes in delivering comprehensive, clinical laboratory services to a wide variety of clients ranging from large tertiary care centers to community hospitals, primary care clinics and long-term care facilities. We also serve as a reference laboratory to a number of other laboratories throughout Wisconsin and northern Illinois. With more than 500 employees, highly sophisticated instrumentation and cutting-edge technology, WDL has the depth, resources and experience to provide exceptional, quality laboratory testing.