||The English used in this article may not be easy for everybody to understand. (June 2012)|
Swine flu is common in pigs. Normally, it only infects people who have been in close contact with pigs. However, the disease has also spread from one person to another. Swine flu can cause fever, disorientation (not being clear-headed), stiffness of the joints, vomiting, and loss of consciousness. Sometimes this ends in death. There are different types, or strains, of swine flu. They are called H1N1, H1N2, H3N1, H3N2, and H2N3..
H1N1 came from the Spanish flu, which caused a pandemic in humans in 1918 and 1919. New viruses came from the Spanish flu. These viruses became common in pigs. Every once in a while, the viruses spread from pigs to humans. This has happened during the 20th century. (However, they happened at the same time as the flu epidemics that happen every year. Because of this, it is hard to tell the difference between 'normal' influenza and swine influenza.) Infections that spread from pigs to humans are rare. Scientists only know of 12 known cases in the United States since 2005.
It is very difficult to prevent the flu virus. This is because the virus changes all the time. If a person gets the flu, his body forms antibodies to fight that virus off if it happens again. But since the flu virus changes all the time, a person's antibodies do not recognize the virus the next time it happens, because it is different. The same thing happens with vaccines.
The changes in the flu virus can cause a flu pandemic. For example, the virus might only change a little bit in about two to three years. After about ten years, most people will have developed antibodies to fight these small changes. But if the virus then changes a lot, there can be a pandemic. Hundreds of millions of people suddenly realize that the antibodies they developed are useless. Even during the Spanish flu pandemic, the first wave of the disease was relatively mild, while the second wave was very deadly.
In 1957, an Asian flu pandemic infected about 45 million Americans and killed 70,000. Eleven years later, from 1968 to 1969, the Hong Kong flu pandemic infected 50 million Americans and caused 33,000 deaths. It also cost about $3.9 billion. In 1976, about 500 soldiers became infected with swine flu over a few weeks. However, by the end of the month, investigators found that the virus had "mysteriously disappeared", and there were no more signs of swine flu anywhere on the post. There were a small number of isolated (far-apart) cases around the U.S. However, these were in people who were thought to have caught the virus from pigs.
Scientists fear the swine flu virus might mutate, or change, into a pandemic as deadly as the 1918/1919 pandemic. They watched the outbreak in 2009, and made plans about what to do if a global pandemic breaks out.
The main symptoms of the swine influenza is much the same as regular influenza. Symptoms include vomiting, nausea, runny nose, (loss of appetite), lethargy (feeling tired), chills, fever, body aches, sore throat, coughing, diarrhea, and stomach ache.
Where swine influenza is found [change]
The bird flu virus H3N2 is endemic in pigs in China. It has recently been found in pigs in Vietnam. Specialists also think that this might lead to new variations of the influenza virus. Pigs can carry human influenza viruses. These viruses can combine in new ways, and exchange certain genes with H5N1. Through mutation, this would create a form of the virus that can pass easily among humans. H3N2 evolved from H2N2 by antigenic shift. In August 2004, researchers in China found H5N1 in pigs.
In 2005 it was discovered that H5N1 could be infecting up to half of the pig population in some areas of Indonesia, but without showing symptoms. Chairul Nidom, a virologist at Airlangga University's tropical disease center in Surabaya, East Java, did some independent research: he tested the blood of 10 apparently healthy pigs housed near poultry farms in West Java where avian flu had broken out, Nature reported. Five of the pig samples contained the H5N1 virus. The Indonesian government has since found similar results in the same region. Additional tests of 150 pigs outside the area were negative.
Swine Flu in Humans [change]
The Centers for Disease Control and Prevention (CDC), a United States government agency, reports that the symptoms and transmission of the swine flu from human to human is much like seasonal flu. Usually, the symptoms are fever, lethargy (feeling tired), lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhoea. It is believed to be spread between humans when an infected person coughs or sneezes and then touches something. Another person then might touch the same thing with the virus on it and then touch their own nose or mouth. The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can be contagious for up to ten days. Diagnosis can be made by sending a specimen (sample), collected during the first five days, to the CDC for analysis.
The Swine Flu is susceptible to four licensed drugs in the United States, amantadine, rimantadine, oseltamivir and zanamivir. However, for the 2009 outbreak, it is recommended it be treated with oseltamivir and zanamivir. The vaccine for the human seasonal flu does not protect against the swine flu. Even if the virus strains are the same specific variety, the antigenicity is very different.
Veterinary swine flu vaccine [change]
The virus has evolved in recent decades. This has made Swine influenza a bigger problem, mainly because traditional vaccines against influenza do not always work against Swine influenza. There are special vaccines against Swine influenza, but they only work if the virus strain is similar to some extent. In the cases more difficult to treat, special vaccines are produced. These are very similar, as they are made to match the specific virus strain.
Present vaccination strategies for SIV control and prevention in swine farms, typically include the use of one of several bivalent SIV vaccines commercially available in the United States. Of the 97 recent H3N2 isolates examined, only 41 isolates had strong serologic cross-reactions with antiserum to three commercial SIV vaccines. Since the protective ability of influenza vaccines depends primarily on the closeness of the match between the vaccine virus and the epidemic virus, the presence of non-reactive H3N2 SIV variants suggests that current commercial vaccines might not effectively protect pigs from infection with a majority of H3N2 viruses.
The current vaccine against the seasonal influenza strain H1N1 is thought unlikely to provide protection. The director of CDC's National Center for Immunization and Respiratory Diseases said that the United States' cases were found to be made up of genetic elements from four different flu viruses—North American swine influenza, North American avian influenza, human influenza A virus subtype H1N1, and swine influenza virus typically found in Asia and Europe. On two cases, a complete genome sequence had been obtained. She said that the virus is resistant to amantadine and rimantadine, but susceptible to oseltamivir (Tamiflu) and zanamivir (Relenza).
2009 outbreak [change]
The new strain of swine influenza A is called H1N1 is responsible for the swine flu outbreak in 2009 in humans. It resulted from a combination of several strains of influenza in humans and influenza in birds as well as swine influenza. Tests were done, they found that the hemagglutinin (HA) gene was similar to that of swine flu viruses present in United States pigs since 1999, but the neuraminidase (NA) and matrix protein (M) genes resembled versions present in European swine. Viruses that were built like this had not been found in humans or pigs before. There is no program to monitor what viruses are circulating in pigs in the United States, however. People currently ignore where this new strain of viruses came from.
The first known case was a five year old boy, named Edgar Hernandez. The boy had been near a pig farm in La Gloria, Veracruz state in Mexico. This farm raises almost one million pigs a year. People living nearby have been complaining about the clouds of flies. These flies are attracted by so-called manure lagoons, which is one of the problems such large farms have. It was first thought the boy had a normal influenza. Laboratory tests showed, however, that he had contracted swine flu. The boy fully recovered.
"If the people who are supposed to be familiar with this didn't know what it was, how will we ever know how my son got it?" Edgar's mother, Hernandez said.
La Gloria, Perote, Veracruz is a small community, surrounded by large pig farms. Reports indicate that during February 2009 over 400 people in the town had flu like symptoms and 2 infants died of 'pneumonia'.
Juan Rodriguez died of 'pneumonia' February 9th at age 7 months.
Yovanni Apolinar also died of 'pneumonia' March 12th aged 2 months.
An unidentified Mexican toddler contracted swine flu in Brownsville, Texas, United States and died April 29th in Houston, Texas, United States at age 23 months.
The United States Department of Agriculture researchers say that while pig vaccination keeps pigs from getting sick, it does not block infection or shedding of the virus.
Dr. Anne Schuchat, interim Deputy Director for CDC Science and Public Health, said that the American cases were found to be made up of genetic elements from four different flu viruses – North American swine influenza, North American avian influenza (bird flu), human influenza, and swine influenza virus typically found in Asia and Europe – "an unusually mongrelised mix of genetic sequences." Pigs have been shown to act as a potential "mixing vessel" in which reassortment can occur between flu viruses of several species. This new strain appears to be a result of reassortment of human influenza and swine influenza viruses, presumably due to superinfection in an individual human. Influenza viruses readily undergo reassortment due to antigenic shift because their genome is split between eight pieces of RNA (see Orthomyxoviridae).
The current strain of swine flu can adapt to humans and spread more efficiently than previously known swine H1N1 strains. Moreover, co-infection of H1N1 swine flu and Oseltamivir resistant H1N1 season flu can lead to acquisition of the H274Y mutation by the swine flu via recombination or reassortment. Swine H1N1 with human H1 and N1 have been reported.
The 1918 flu pandemic strain had undergone polymorphism from swine and human H1N1 in all eight pieces of RNA gene segments. Similar swapping of gene segments in humans co-infected with seasonal human influenza and swine H1N1 can lead to rapid evolution.
Other pages [change]
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- "World Health Organization: Swine flu could spread globally". CNN.com. http://www.cnn.com/2009/HEALTH/04/25/swine.flu/index.html. Retrieved 2009-04-25.
- "Swine Influenza". Swine Diseases (Chest). Iowa State University College of Veterinary Medicine. http://www.vetmed.iastate.edu/departments/vdpam/swine/diseases/chest/swineinfluenza/.
- eurekalert Tips from the Journals of the American Society for Microbiology - Novel H3N1 Swine Influenza Virus Identified in Pigs in Korea
- PNAS Published online before print December 18, 2007, doi: 10.1073/pnas.0710286104 PNAS December 26, 2007 vol. 104 no. 52 20949-20954
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- "Soft evidence and hard sell". New York Times. 5 September 1976. http://select.nytimes.com/gst/abstract.html?res=F10914FA3E5E14768FDDAC0894D1405B868BF1D3&scp=9&sq=Swine+Flu+epidemic&st=p.
- "U.S. pork groups urge hog farmers to reduce flu risk". Reuters. 26 April 2009. http://www.reuters.com/article/latestCrisis/idUSN26488473.
- "The Last Great Swine Flu Epidemic", Salon.com, April 28, 2009
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- "Bird flu and pandemic influenza: what are the risks?". UK Department of Health. http://www.dh.gov.uk/en/Aboutus/MinistersandDepartmentLeaders/ChiefMedicalOfficer/Features/DH_4102997.
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- "Q & A: Key Facts about Swine Influenza (Swine Flu) – Diagnosis". Centers for Disease Control and Prevention. 24 April 2009. http://www.cdc.gov/swineflu/key_facts.htm. Retrieved 2009-4-26.
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- Rob Stein (23 April 2009). "In California and Texas, 5 New Swine Flu Cases". Washington Post. http://www.washingtonpost.com/wp-dyn/content/article/2009/04/23/AR2009042304116.html.
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- Mexico outbreak traced to 'manure lagoons' at pig farm, Times Online, April 28, 2009
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- Robert Roos (2007-12-20). "New swine flu virus supports 'mixing vessel' theory". http://www.cidrap.umn.edu/cidrap/content/influenza/avianflu/news/dec2007swine.html.
- "Identification of H2N3 influenza A viruses from swine in the United States". 2007-12-26. doi:10.1073/pnas.0710286104. http://www.pnas.org/content/104/52/20949.abstract.
- "Human Transmission of Swine H1N1 in Southern California". 2007-04-22. http://www.recombinomics.com/News/04220902/H1N1_CA_Swine_H2H.html.
- "WHO raises H1N1 Virus to Stage 5 -Pandemic Eminent". 2009-04-29. http://politicolnews.com/who-raises-h1n1-to-stage-5/.
Further reading [change]
- "Swine Flu Cases Without Swine Exposure" Center for Biosecurity of UPMC
- Swine Flu h1n1
- The Swine Flu Affair: Decision-Making on a Slippery Disease Original 1978 U.S.A. Department of Health Education and Welfare review by Richard E. Neustadt and Harvey V Fineberg available from Louisiana State University Law Center Medical and Public Health Law Site.
- Surface sanitation and interruption of influenza using NAV-CO2
- The Swine Flu Episode and the Fog of Epidemics by Richard Krause in CDC's Emerging Infectious Diseases Journal Vol. 12, No. 1 January 2006 published December 20, 2005
- SWINE INFLUENZA by Carol G. Woodlief of College of Veterinary Medicine at North Carolina State University Overview, symptoms in pigs, treatment for pigs
- In California and Texas, 5 New Swine Flu Cases Washington Post, By Rob Stein (Staff Writer)
- Swine Flu In Mexico And U.S. May Lead To Pandemic, WHO Says AHN, Mayur Pahilajani (Staff Writer)
- News and information on the 2009 human swine flu outbreak
- H1N1 Swine Flu cases tagged on Google Maps