What Types of Flu Are There?

When it comes to the flu, not all types are created equal. According to the CDC, there are four types of influenza viruses: influenza A, influenza B, influenza C, and influenza D. Influenza A and B are the two main types that routinely spread in humans and cause seasonal flu epidemics. Influenza C viruses cause only mild respiratory infections and are not thought to be responsible for epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

Influenza A vs B: Brief History & Transmission

Influenza A viruses are the most harmful, as they can cause severe disease. Wild aquatic birds are often the hosts for a large variety of influenza A viruses. Sometimes these viruses are transmitted from bird to human and can cause devastating outbreaks. Some of the subtypes of influenza A that have caused the largest number of known human deaths are:

  • H1N1, which caused Spanish Flu in 1918 and Swine Flu in 2009
  • H2N2, which caused Asian Flu in 1957
  • H3N2, which caused Hong Kong Flu in 1968
  • H5N1, which caused Bird Flu in 2004

Influenza B almost exclusively infects humans and is less common than influenza A. Because humans are the natural host of influenza B, pandemics generally do not occur with influenza B viruses.

Influenza C viruses are milder and do not cause epidemics. Seasonal flu vaccines, which contain strains of influenza A and B, do not protect against influenza C viruses.

Do You Have the Flu?

The good news is most people will recover from the flu on their own. However, if you have a severe case of the flu, you should call our office to make an appointment. Not sure if you have the flu? The CDC lists flu symptoms and complications here.

If you do in fact have the flu, antiviral drugs can be used to treat types A, B, and C and speed recovery by 1 or 2 days. But the CDC stresses that these drugs are a second line of defense against the flu after vaccination, which is the best way to prevent seasonal influenza in the first place.

Certain populations are more susceptible to getting the flu, including the very young, the elderly, and people with a compromised immune system. If you feel sick and it’s not an emergency, please call us at Prosperity Internal Medicine at 703-876-9300 for an appointment. Our group uses the latest advances in medicine, offering our patients access to innovative health management technologies, proactive team-based care, and an evidenced-based, patient-centered approach.