People can get the various types of flu directly or indirectly. For example, when a person coughs, the virus travels into the air and anyone within range of the airborne virus can become infected. The other way to pick up the flu virus comes from touching an object and then touching the face, mouth or nose. The virus becomes transmitted indirectly this way. Three general classifications of influenza exist, MayoClinic.com reports, namely influenzavirus A, B and C.
Influenza A
This type includes the swine flu or H1N1, the avian or bird flu, also known as H151, and the epic Spanish Flu of 1918-19, the U.S. Centers for Disease Control and Prevention reports. The recent H1N1 viral variation classifies as a “distant cousin” of the Spanish Flu that spread around the world following the cessation of hostilities at the end of World War I. The Spanish flu was the first global pandemic of the 20th century in which approximately one in five people living at the time were infected. The advent of H1N1 swine flu in early 2009 prompted the World Health Organization to declare a pandemic in that year. This prompted the governments of the world to work to produce a vaccination to help prevent people from getting the swine flu. Vaccinations against the seasonal flu may include strains to help fight both influenzavirus A and B. Type A generally causes the most widespread infections and the most serious illnesses, especially for the elderly and very young children.
Influenza B
The influenzavirus B, unlike A or C, usually only infects humans, the U.S. Centers for Disease Control and Prevention reports. This version of the flu can cause epidemics, meaning the contagion can spread across states or regions, but rarely farther. Symptoms, such as a fever, chills, a cough, sore throat and nasal congestion, appear similar to flu virus A. The only other mammal susceptible to the B virus is the seal.
Influenza C
This flu type has mild respiratory symptoms. It does not have the pandemic effects that other flu strains may have, the U.S. Centers for Disease Control and Prevention reports. This strain typically affects a smaller physical area, such as a school or town population. Symptoms may occur similar to the other strains, but in general will not occur as severe problems.
