Flu is caused by three types or strains of viruses: influenzavirus A, influenzavirus B and influenzavirus C. Type A influenza is the most severe form and is responsible for deadly pandemics which strike every few decades and is characterized by constant mutations. It can be subdivided into different subtypes according to the antibody response to the viruses. Both the Spanish flu which had killed about 50 million of people worldwide in 1918 and the swine flu which emerged in Mexico in April 2009 are classified as influenza A virus subtype H1N1. However, so far the majority of people infected with the swine flu experienced only mild symptoms similar to those in seasonal flu and recovered in few days. Despite that the majority of health experts recommend vaccination especially for people who have a chronic medical condition and are at higher risk of developing complications.

Like type A influenza, type B influenza is constantly changing but slower than influenzavirus A. Despite that it can also cause global epidemics but rarer than type A influenza virus. Influenza B outbreaks are commonly smaller and remain limited to certain regions. Unlike A and B influenza strains, influenzavirus C is relatively stable which means it evolves much slower than A and B strains. C influenzavirus is more rare than A and B types but it can cause local epidemics.

All influenzaviruses are transmitted by saliva and nasal secretions of an infected person through close physical contacts and air via aerosols. However, you can also pick germs up from a contaminated surface or an object such as door handle, computer keyboard, etc. and transfer them from your hands to your nose, mouth or eyes.

Related posts:

1. About Flu – FAQ’s about flu
2. Swine Flu – What is swine flu
3. Symptoms of Swine Flu – Sign and symptoms of novel H1N1 flu
4. Swine Flu Vaccines – Safety and efficacy of the vaccines against the novel H1N1 flu virus
5. Flu Prevention – Useful tips how to prevent getting flu
6. Flu Symptoms – Signs and symptoms of flu
7. Flu Vaccination – Benefits and side effects of flu vaccine

This entry was posted on Friday, December 25th, 2009 at 10:58 am and is filed under Flu. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.