Influenza viruses are single-stranded RNA viruses belonging to the Orthomyxovirus family. They can mutate quickly, which makes development of effective vaccines and antiviral agents a challenge. Influenza A viruses cause most outbreaks and are more pathogenic than other types of influenza viruses. In the spring of 2009, a triple-reassortant strain of influenza A (H1N1) that contained swine, avian, and human genes caused several outbreaks in Mexico and the United States; new cases were soon reported worldwide. On June 11, 2009, WHO declared a global pandemic based on 30,000 cases of H1N1 influenza in 74 countries.
Common Cold can be caused by more than 200 types of viruses. However, the rhinovirus and coronavirus are the most common causes.
- Rhinovirus is most active in early fall, spring, and summer (10%-40%). They rarely make you seriously sick.
- Coronavirus is most active in the winter and early spring (20%).
- RSV and parainfluenza (20%). They sometimes lead to severe infections, like pneumonia, in young children.
On the other hand, research suggests that stress and allergies that affect your nose or throat may raise your chances of getting infected by a cold virus. There is no evidence that you can get a cold from exposure to cold weather or from getting chilled or overheated.
Reference
Erlikh, I. V., et al., 2010, ' Management of influenza', Am Fam Physician, vol. 82, no.9, pp. 1087-1095.
Worrall, G., 2007,'Common cold', Can Fam Physician, vol. 53, no. 10, pp. 1735–1736.
www.cdc.gov/flu/symptoms/coldflu.htm
www.webmd.com/cold-and-flu/cold-guide/common_cold_causes
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