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Influenza Virus: Why the Flu Is the Smartest Virus Around

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INFLUENZA VIRUS
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Thousands of people around the world are diagnosed with influenza each year. [1] Even more do not receive an official diagnosis, but still have what is commonly known as "the flu."

It often starts as a cough, sore throat, chills, fever, or even just aches, and is easily confused with the common cold. [2] What many do not understand is that the influenza virus is both a serious respiratory condition and one of the "smartest" viruses around. [3]

The history of the influenza virus can be traced back more than 800 years. Before 1932, when the virus was first identified in a laboratory, the virus's progression was tracked by written histories of the disease symptoms. [4]

The first influenza epidemic was reported in 1173 CE. [5] The most recent influenza pandemic was the H1N1 strain, which sickened millions and led to more than 18,000 deaths globally in 2009-10. [6]

Although we generally refer today to a single influenza virus, there are actually many forms of influenza virus, none of which are either the same virus identified in 1932 or the virus our ancestors suffered from 800 years ago. While all varieties of influenza are RNA-type viruses that attack the respiratory system, the molecular biology of each virus mutates frequently, effectively trying to "outsmart" those of us physicians and scientists who strive to keep the virus at bay. [7]

So let's take a look at exactly what this ever-changing influenza virus really is. There are three types of influenza viruses -- A, B and C. [1] Influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. Influenza A is the most common and is a quickly mutating serotype and is often more debilitating than the Influenza B virus. Influenza type C infections cause a mild respiratory illness and are not thought to cause epidemics. [1]

All three influenza viruses continually mutate to "trick" the body's immune system. Each year, we develop antibodies against one strain of influenza but the virus often changes the next year and leaves us at risk again. In some cases, the antibodies developed from previous years may provide some protection against the new influenza virus, but that is not a game of chance we want to take and why there is a need of annual vaccination. [8]

As antiviral drugs are only effective if given early, it is more important to vaccinate as many people as possible before the start of flu season. [9] Each year, the World Health Organization's (WHO) scientists look at the influenza viruses and predict which three, two influenza A and one influenza B viruses, will be the most prevalent during the upcoming season. [10] Pharmaceutical companies then develop vaccines that provide the most protection against those predicted viruses.

Since influenza viruses are continually "drifting" by undergoing small changes from one season to the next or even within the course of one flu season, it is impossible to predict with complete certainty which influenza viruses will be predominate or the severity, timing or duration of an influenza season. The vaccine can cross-protect against circulating viruses. Antibodies created through vaccination with one strain of influenza viruses will often offer protection against different, but related strains of influenza viruses.

The influenza virus is easily transmitted from person-to-person and we all are at risk for contracting influenza. For some, this will only mean lost work or school days, but for those at highest risk, the results can be more serious, leading to hospitalization and even death. Although sanitizing your home, work and other spaces can slow the virus progression, vaccination is the optimal way to prevent influenza outbreaks. [11, 12]

The U.S. Centers for Disease Control and Prevention (CDC) recommends annual influenza immunization for everyone over six months of age. Groups at higher risk of influenza infection or complications include [11]:

  • People 50 years of age and older
  • Children six months-18 years of age
  • Pregnant women
  • People of any age with certain chronic medical conditions, such as asthma, chronic obstructive pulmonary disease (COPD), heart disease, diabetes and others
  • Residents of long-term care facilities and nursing homes

What puzzles many of us in the health care industry is that although protection against the virus is a simple vaccination, influenza immunization rates fall far short of public health goals every year -- even among those at highest risk. Studies have shown that influenza outbreaks typically start in areas in which the population has little or no immunity. This can be either because of a mutation to the virus or, as with some developing countries or rural areas, vaccination is sparse. [13]

Why are immunization rates for many groups low? Is it the product of complacency in those who have never had influenza, or something else? Whatever the reason, it is important to be vaccinated annually each flu season. Contrary to popular belief, however, the vaccine may not make you sick. According to the CDC, it is safe and effective. [11] If you do get sick immediately after receiving the vaccine, it is likely that you either were exposed to the virus either before or within two weeks after receiving the vaccine, when your body is building immunity against the strains or that it was a new strain not accounted for in the vaccine. [2, 14]

It is important to learn as much as you can about the seasonal influenza virus and vaccine to protect yourself and your loved ones. The American Lung Association's Faces of Influenza campaign is a great place to get educated and find a location to get your influenza vaccine if you haven't already. It is rarely "too late" to get vaccinated, as flu season usually lasts well into the spring, with virus activity peaking in February or March in most years.

More knowledge about this serious illness is just one click away at www.facesofinfluenza.org.

References
1 The Centers for Disease Control Keys Facts About Influenza and the Flu Vaccine. Accessed December 20, 2010. http://www.cdc.gov/flu/keyfacts.htm

2 The Centers for Disease Control Keys Facts About Influenza and the Flu Vaccine. Accessed December 20, 2010. http://www.cdc.gov/flu/keyfacts.htm

3 C.W. Potter, Division of Molecular and Genetic Medicine, University of Shefield Medical School, Shefield, UK and Department of Pathology, Perak College of Medicine, Ipoh, Perak Darul Ridzuan, Malaysia, Journal of Applied Microbiology 2001, p. 572

4 C.W. Potter, Division of Molecular and Genetic Medicine, University of Shefield Medical School, Shefield, UK and Department of Pathology, Perak College of Medicine, Ipoh, Perak Darul Ridzuan, Malaysia, Journal of Applied Microbiology 2001, p. 572

5 C.W. Potter, Division of Molecular and Genetic Medicine, University of Shefield Medical School, Shefield, UK and Department of Pathology, Perak College of Medicine, Ipoh, Perak Darul Ridzuan, Malaysia, Journal of Applied Microbiology 2001, p. 574

6 World Health Organization Pandemic Update 112, August 2010. Accessed December 20, 2010. http://www.who.int/csr/don/2010_08_06/en/index.html

7 WHO position paper: influenza vaccines WHO weekly Epidemiological Record 19 August 2005, vol. 80, 33, pp.282. Accessed December 20, 2010. http://www.who.int/wer/2005/wer8033.pdf

8 Medicine.net. Why Should the Flu Vaccine Be Taken Every Year. Accessed December 20, 2010. http://www.medicinenet.com/influenza/article.html

9 The Centers for Disease Control, "Key Facts About Anitviral Drugs and Influenza. Accessed December 20, 2010. http://www.cdc.gov/flu/protect/antiviral/keyfacts.htm

10 World Health Organization, "Recommended Viruses for Influenza Vaccines for Use in the 2010-2011 Northern Hemisphere Influenza Season." Accessed December 20, 2010. http://www.who.int/csr/disease/influenza/recommendations2010_11north/en/index.htm

11 Centers for Disease Control and Prevention (CDC). Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2010. MMWR. 2010;59(RR-8):1-62.

12 Centers for Disease Control and Prevention. "How To Clean and Disinfect Schools To Help Slow the Spread of Flu." Accessed December 20, 2010. http://www.cdc.gov/flu/school/cleaning.htm

13 Medicine.net. Why Should the Flu Vaccine Be Taken Every Year. Accessed December 20, 2010. http://www.medicinenet.com/influenza/article.html

14 Holmes, E; Ghedin E, Miller N, Taylor J, Bao Y, St George K, Grenfell B, Salzberg S, Fraser C, Lipman D, Taubenberger J (2005). "Whole-genome analysis of human influenza A virus reveals multiple persistent lineages and reassortment among recent H3N2 viruses". PLoS Biol 3 (9): e300. doi:10.1371/journal.pbio.0030300. PMID 16026181. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1180517/?tool=pmcentrez

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