When you hear that someone has the flu, you probably think of aches, pains and fever that are associated with it. While these are common flu symptoms, the Center for Disease Control and Prevention (CDC) reports that there are actually three different types of influenza viruses, and all three, while similar in some ways, are very different in others.
Type A Influenza
Type A flu viruses are broken down into further classifications, and these are based upon the two proteins, H (hemagglutinin) and N (neuraminidase) that appear on the surface of the virus. The CDC reports that H has 16 subtypes, and N has 9 subtypes. For example, one classification of type A influenza is what is commonly known as the "swine flu," and this is categorized as H1N1. Another type A influenza is H5N1, also known as "bird flu" or "avian flu." Type A influenza is present in humans and can cause pandemics, which means it is an infectious disease that can affect widespread areas and populations. The National Institute of Allergy and Infectious Diseases reports that type A flu viruses are often found in ducks, chickens, dogs, pigs and even whales, as well as humans. Type A influenza symptoms are fever, body aches and pains, cold chills, cough, sore throat, runny and/or stuffy nose, fatigue and occasional intestinal distress. Seasonal flu is also considered type A.
Type B Influenza
The type B influenza virus spreads more slowly than type A, but it exhibits the same symptoms as type A, only less severe. According to Cornell University, type B is usually only found in people and not in animals. However, a report from the American Association for the Advancement of Science states that the B virus has been found in seals. While type B does not cause pandemics, it can cause an epidemic, which means that it can affect several people at once in an area or community.
Type C Influenza
The CDC reports that type C influenza causes mild respiratory illness, and the symptoms are not as severe as those in type A and type B flu. Symptoms are usually coughing and respiratory congestion. It is found in humans and animals and does not cause a pandemic or an epidemic. While the seasonal flu vaccine is said to protect against type A and type B influenza, it does not offer protection against type C.
