Influenza or ‘flu’ is a common viral infection that affects the respiratory tract (nose, bronchi, lungs, throat, etc) and results in fever, headache, cough, nasal discharge and constitutional symptoms. In the US, annually about 5 to 20 % of the population are affected with a bout of flu. About 200,000 people each year develop flu-related complications and require admission each year, and about 36,000 have fatal outcomes from flu-related complications (CDC, 2009). Usually certain groups of people are at the high-risk of developing flu-related complications including infants, children, elders, asthmatics, diabetics and those suffering heart diseases. The infection is transmitted from one individual to another by droplets that are produced during sneezing, coughing, exhaling, etc. Using contaminated personal items of the individual can also result in transmission of the infection. The incubation period of the infection ranges from 1 to 5 days (WHO, 2009). During certain seasons, the number of cases of influenza would go up.
The symptoms and signs of influenza include cough, sore throat, running nose, breathing difficulties, fatigue, headache, body ache, nausea, vomiting, anorexia, malaise, diarrhea, etc. The complications of influenza include pneumonia, ear infection, sinusitis, dehydration, meningitis, and exacerbation of any chronic generalized disorder. People infected with flu usually get better by themselves, requiring only supportive treatment within a period of one to two weeks (CDC, 2009).
Influenza is a seasonal disorder and tends to occur more frequently during the cold season. From December to March, the flu activity would peak in the US. From March to May, the flu activity in the US would decrease. It has been observed that during the last 16 years, the flu activity would peak in the month of February. More than 50 states in the US have peak flu activity during the month of February (CDC, 2009). Every year, a huge number of children die from flu-complications especially influenza. In the year 2007-08, the same number of children died from flu-related complications than in 2004-05 (CDC, 2009).
One of the worst years in which the influenza pandemic affected the world was in 1918, when more people died from flu than the World War 1 or the Black Deaths of plague in the 14th century. This episode of flu deaths was also known as ‘La Grippe’ and more than 20 % of the world’s population was somehow affected with the condition. More than 50 % of the soldiers who died in Europe had met their end due to influenza rather than being killed by their enemy. It was estimated that about 20 to 40 million people died from the Influenza pandemic of 1918 (Billings, 2005). In the year 1957 about 2 million people died in Asia due to an Asian influenza pandemic. In the year 1968, about 1 million people died in Hong Kong due to an epidemic of influenza. H5N1 strain of influenza caused 6 deaths in Hong Kong (WHO, 2009)
The strains of viruses that cause influenza epidemics and pandemics vary from one season to another. In the year 1999-2000, it was influenza type 1 (H3N2) that was predominant. In the following season it was influenza A (H1N1) that was predominant, followed by H3N2 that predominated. In 2002-03, it was the influenza A (H1) and B groups that were predominating followed by H3N2 in 2003-04 till 2005-06. In 2006-07 and 2007-08, there influenza A (H1) along with influenza A (H3) predominated. In the year 2008-09, a novel form of influenza A (H1N1) has been occurring throughout the world in epidemic proportions. In 2003-04, there were high rates of avian flu (H5N1) throughout the world (CDC, 2009).
It has been clearly seen that Influenza is usually a self-limiting disease which tends to spread easily from one individual to another. The ability of the strain to cause mortality depends on several factors including number of people affected with the disease, the potency or virulence of the virus, the characteristics of the populations infected and the manner in which preventive measures and treatments are undertaken. Once the infection crosses the limiting proportions and enters into epidemic proportions, there are chances that the virus would be changing its characteristics and would be causing serious infection in human beings. Every year the strain predominating keep changing due to the preventive measures taken to protect against the virus (WHO, 2009).
Billing, M. (2005). The Influenza Pandemic of 1918, Retrieved on July 4, 2009, from Web site: http://www.stanford.edu/group/virus/uda/
CDC (2009). Influenza, Retrieved on July 4, 2009, from Web site: http://www.cdc.gov/flu/
CDC (2009). Flu Activity & Surveillance, Retrieved on July 4, 2009, from Web site: http://www.cdc.gov/flu/weekly/fluactivity.htm
CDC (2009). 2007-2008 Influenza (Flu) Season, Retrieved on July 4, 2009, from Web site: http://www.cdc.gov/flu/about/qa/season.htm
WHO (2009). Influenza, Retrieved on July 4, 2009, from Web site: http://www.who.int/topics/influenza/en/