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Influenza "(flu) is infection of the lungs and airways with one of the influenza viruses, causing a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general feeling of illness (malaise). Influenza is distinctly different from the common cold. It is caused by a different virus and produces symptoms that are more severe. Also, influenza affects cells much deeper down in the respiratory tract."[http://www.merck.com/mmhe/sec17/ch198/ch198c.html?qt=flu&alt=sh#sec17-ch198-ch198c-840 Merck Influenza is a contagious Disease among Bird s and Mammal s, caused by an RNA Virus of the Orthomyxoviridae family. It rapidly spreads around the world in seasonal Epidemics , killing millions of people in pandemic years and hundreds of thousands in nonpandemic years. It creates health care costs and lost productivity. Three influenza Pandemics in the 20th Century , each following a major genetic change in the Virus , killed millions of people all over the world. The world's current major Influenza Pandemic threat is H5N1 ; but it is at present mostly a flu in birds, not in people. Gastroenteritis is commonly called "stomach flu" or "24 hour flu"; but that is a misnomer as it is not connected with actual flu which is a disease caused by Orthomyxoviridae viruses. The term influenza has its origins in 15th century Italy, where the cause of the disease was ascribed to unfavourable Astrological ''influences''. Evolution in medical thought led to its modification to "influenza di freddo", meaning "influence of the cold", which by the 18th century became the prevalent terminology in the English-speaking world as well. HISTORY See Also: influenza pandemic pandemic.]] "Influenza was first described by Hippocrates as early as 412 b.c., and the tiny virus has spent the succeeding centuries shifting, drifting and wreaking havoc. Humanity has been seeking ways to eliminate the threat since the first pandemic was recorded in 1580." This article , in 2003 , was published in American Scientist by world renowned virologist Robert Webster . Its title is ''The world is teetering on the edge of a pandemic that could kill a large fraction of the human population''. "The fact that flu is caused by a virus was a British discovery, made in 1933 by scientists of the Medical Research Council (MRC)." Times on-line ''Battle of time, luck and science'' - published April 09, 2006 The most known outbreaks are caused by Antigenic Shift , when two strains of influenza recombine forming a lethal new strain. The most famous outbreak (and the most lethal) was the so-called Spanish Flu Pandemic ( Type A Influenza , H1N1 strain), which lasted from 1918 to 1919 , and is believed to have killed more people in total than World War I . While the war casualties accumulated over several years, the pandemic took most of its toll over a period of weeks. Lesser flu epidemics included the 1957 Asian Flu (type A, H2N2 strain) and the 1968 Hong Kong Flu (type A, H3N2 strain). ;Known flu pandemics Influenza PDF
Although there were scares in New Jersey in 1976 (the Swine Flu ), worldwide in 1977 (the Russian Flu ), and in Hong Kong (as well as in other Asian countries, namely continental China, as became known later) in 1997 ( Avian Influenza ), there have been no major pandemics subsequent to the 1968 infection. Increased immunity from Antibodies , and the development of Flu Vaccine s have limited the spread of the virus, and so far prevented any further pandemics. SYMPTOMS "Symptoms start 24 to 48 hours after infection and can begin suddenly. Chills or a chilly sensation are often the first indication of influenza. Fever is common during the first few days, and the temperature may rise to 102 to 103° F. Many people feel sufficiently ill to remain in bed for days; they have aches and pains throughout the body, most pronounced in the back and legs. Headache is often severe, with aching around and behind the eyes. Bright light may make the headache worse. At first, the respiratory symptoms may be relatively mild, with a scratchy sore throat, a burning sensation in the chest, a dry cough, and a runny nose. Later, the cough can become severe and bring up sputum. The skin may be warm and flushed, especially on the face. The mouth and throat may redden, the eyes may water, and the whites of the eyes may become bloodshot. The ill person, especially a child, may have nausea and vomiting. A small percentage of people with influenza lose their sense of smell for a few days or weeks; rarely, the loss is permanent." The virus attacks the Respiratory Tract , is transmitted from person to person by saliva droplets expelled by coughing, and causes the following Symptoms :
Influenza's effects are much more severe than those of the " Cold ", and last longer. Recovery takes about one to two weeks. Influenza can be deadly, especially for the weak, old or chronically ill. Some flu Pandemics have killed millions of people. Most people who get influenza will recover in one to two weeks, but others will develop life-threatening complications (such as Pneumonia ). Millions of people in the United States (about 10% to 20% of U.S. residents) are infected with influenza each year. An average of about 36,000 people per year in the United States die from influenza, and 114,000 per year are admitted to a hospital as a result of influenza. According to estimates by the World Health Organization , between 250,000 and 500,000 die from influenza infection each year worldwide. Even healthy people can be affected, and serious problems from influenza can happen at any age. People age 65 years and older, people of any age with chronic medical conditions, and very young children are more likely to get complications from influenza. Pneumonia , Bronchitis , Sinus , and Ear Infection s are four examples of such complications. The flu can make chronic health problems worse. For example, people with asthma may experience Asthma attacks while they have the flu, and people with chronic Congestive Heart Failure may have a worsening of this condition, that is triggered by the flu. FLU SEASON See Also: Flu season Influenza reaches peak prevalence in Winter , and because the Northern and Southern Hemisphere have winter at different times of the year, there are actually two flu seasons each year. Therefore, the World Health Organization (assisted by the National Influenza Centers ) makes two Vaccine formulations every year; one for the Northern, and one for the Southern Hemisphere. While most influenza outbreaks in the Northern Hemisphere tend to peak in January or February, not all do. For example, the Influenza Pandemic Of 1918 And 1919 reached peak virulence during late spring and summer worldwide, and not until October in the US. It remains unclear why outbreaks of the flu occur seasonally rather than uniformly throughout the year. One possible explanation is that, because people are indoors more often during the winter, they are in close contact more often, and this promotes transmission from person to person. Another is that cold temperatures lead to drier air, which may dehydrate mucus, preventing the body from effectively expelling virus particles. The virus may also linger longer on exposed surfaces (doorknobs, countertops, etc.) in colder temperatures. Increased travel and visitation due to the holiday season may also play a role. NPR PREVENTION It is possible and in many cases recommended to get vaccinated against influenza with a Flu Vaccine . Its effectiveness varies with many criteria. Due to the high mutability of the virus, a particular flu vaccine formulation usually only works for about a year. The World Health Organization co-ordinates the contents of the vaccine each year to contain the most likely strains of the virus that probably will attack the next year. It is possible to get vaccinated for the season and still catch the flu. The vaccine is reformulated each season for a few specific flu strains, but cannot possibly include all the different strains actively infecting people in the world for that season. This means that you could catch a virus not covered by the vaccine. Also, it takes about six months for the manufacturers to formulate and make the millions of doses required to deal with the seasonal epidemics; occasionally a new or overlooked strain becomes prominent during that six months and infects people even though they've been vaccinated (as in the 2003-2004 season). The vaccine may have partial coverage for these unexpected strains. It is also possible to get infected and then get vaccinated the next day, before flu symptoms appear, and still get sick with the very strain that the vaccine is supposed to prevent. The vaccine can take a few days to become effective. Vaccines can cause the immune system to react as if the body were actually being infected, and general infection symptoms (many cold and flu symptoms are just general infection symptoms) can appear, though these symptoms are usually not as severe or as long lasting as the flu. The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. The risk of a flu shot causing serious harm, or death, is extremely small. However, a vaccine, like any medicine, may rarely cause serious problems, such as severe allergic reactions. Almost all people who get influenza vaccine have no serious problems from it.CDC Personal Health And Hygiene are important in avoiding and minimizing influenza. TREATMENT Main article Flu Treatment contains curative treatments, symptom treatments and unconventional treatments such as antivirals, decongestants, and echinacea, respectively. If you get the flu, get plenty of rest, drink a lot of liquids, and avoid using alcohol and tobacco. You can take medications such as Acetaminophen to relieve the fever and muscle aches associated with the flu. Children and teenagers with flu symptoms (particularly fever) should avoid taking Aspirin as taking aspirin in the presence of influenza infection (especially Influenza Type B ) can lead to Reye Syndrome , a rare but potentially fatal disease of the Liver . CDC RESEARCH See Also: Flu research Influenza research includes Molecular Virology , Pathogenesis , host Immune Response s, and Epidemiology . These help in developing influenza countermeasures such as Vaccine s, therapies and diagnostic tools. Improved influenza countermeasures require basic research on how viruses enter cells, replicate, mutate, evolve into new strains and induce an immune response. The Influenza Genome Sequencing Project is creating a library of influenza sequences that will help us understand what makes one strain more lethal than another, what genetic determinants most affect immunogenicity, and how the virus evolves over time. Solutions to limitations in current vaccine methods are being researched. The US government has purchased from Sanofi Pasteur and Chiron Corporation several million doses of Vaccine meant to be used in case of an Influenza Pandemic from H5N1 and is conducting clinical trials on them. New York Times article ""Doubt Cast on Stockpile of a Vaccine for Bird Flu"" ABC News reported on April 1, 2006 that "Beginning in late 1997, the human trials have tested 30 different vaccines, all pegged to the H5N1 virus." ABC News FLU IN NONHUMANS While all flu is caused by the family of virus species called Orthomyxoviridae , most flu is caused by the species Influenza A Virus which is hosted by birds, but may infect several species of mammals. Variants of flu virus are sometimes named according to the species the strain is endemic in or adapted to. The main variants named using this convention are: Influenza A virus subtype H5N1, also known as H5N1, is a subtype of the Influenza A Virus that is capable of causing illness in many species, including humans. An Asian lineage strain of HPAI A(H5N1) is Spreading Globally . It is Epizootic (an epidemic in nonhumans) and panzootic (a disease affecting animals of many species, especially over a wide area) killing tens of millions of birds and spurring the Culling of hundreds of millions of other birds in an attempt to control its spread. Most references in the media to "bird flu" and most references to H5N1 are about this specific strain. | ||||||||||||||||||||||||||||||
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