xTAG®

Flu versus colds…
and other respiratory mysteries clarified

So what, exactly, is the flu?

There are lots of common misperceptions about flu, viruses and bacterial infections, and it’s important to understand the differences so you can pursue the proper tests and treatment for you or a loved one.

There are three types of influenza viruses: influenza A, influenza B, and influenza C. Types A and B are the ones we usually mean when we say “the flu” –  they’re the ones that spread around the world every year during “flu season”. Influenza C causes a milder illness that usually doesn’t spread widely.

There are many different versions of the influenza A virus. Each strain is named based on the particular version of two proteins – hemagglutinin (H) and neuraminidase (N) – that are found on the virus’ surface. The most common strains that infect humans during seasonal outbreaks are H1N1 and H3N2. The “bird flu” that was a concern recently was a rare case of an H5N1 strain that could infect people. The “swine flu” is an H1N1 strain, but different from the regular, seasonal H1N1 flu.

There are also different versions of the influenza B virus, but they aren’t named with H’s and N’s – the strains are named based on where and when they were first observed.

And how do other viruses fit in?

There are many other viruses that can cause respiratory and other flu-like symptoms. In fact, some of these are far more frequent causes of illness than influenza. The most common ones include:

• Parainfluenza virus
• Respiratory syncytial virus
• Rhinovirus
• Enterovirus
• Coronaviruses
• Human metapneumovirus

Because many of these viruses have similar symptoms, often the only way to tell which one is causing the symptoms is to run a diagnostic test. Rapid tests that are commonly run in doctors’ offices can test for one or two of these viruses at a time.  Tests done in labs such as in hospitals are more comprehensive and reliable than rapids, but can take 3 to 7 days or more to generate an answer. Some molecular tests (e.g., xTAG RVP) can detect many different viruses at once and are able to identify which specific viruses may be present in a patient sample in a matter of hours.