Jump to content

Swine influenza

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Unused0029 (talk | contribs) at 21:43, 27 April 2009 (→Swine flu in humans: clarify what CDC is). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Influenza (flu)
H1N1 virus
Types
Vaccines
Treatment
Pandemics
Outbreaks
See also
Pigs can harbor influenza viruses adapted to humans and others that are adapted to birds, allowing the viruses to exchange genes and create a pandemic strain.

Swine influenza virus (referred to as SIV) refers to influenza cases that are caused by Orthomyxoviruses that are endemic to pig populations. SIV strains isolated to date have been classified either as Influenzavirus C or one of the various subtypes of the genus Influenzavirus A.[1]

Swine flu, unlike bird flu, is able to pass from human to human contact.[2]

Swine influenza is known to be caused by influenza A subtypes H1N1,[3] H1N2,[3] H3N1,[4] H3N2,[3] and H2N3.[5]

In swine, three influenza A virus subtypes (H1N1, H3N2, and H1N2) are circulating throughout the world. In the United States, the H1N1 subtype was exclusively prevalent among swine populations before 1998; however, since late August 1998, H3N2 subtypes have been isolated from pigs. As of 2004, H3N2 virus isolates in US swine and turkey stocks were triple reassortants, containing genes from human (HA, NA, and PB1), swine (NS, NP, and M), and avian (PB2 and PA) lineages.[6]

Classification

SIV strains isolated to date have been classified either as Influenzavirus C or one of the various subtypes of the genus Influenzavirus A.[7]

Signs and symptoms

Main symptoms of swine flu in humans.[8]

The Centers for Disease Control and Prevention (CDC) have stated that the symptoms of swine flu are similar to those of other strains of human flu, including fever, cough, sore throat, body aches, headache, chills and fatigue. A few patients have reported that they also suffered from diarrhea and vomiting.[9]

Causes

H5N1

Avian influenza virus H3N2 is endemic in pigs in China and has been detected in pigs in Vietnam, increasing fears of the emergence of new variant strains.[10] Health experts[who?] say pigs can carry human influenza viruses, which can combine (i.e. exchange homologous genome sub-units by genetic reassortment) with H5N1, passing genes and mutating into a form which can pass easily among humans.[11] H3N2 evolved from H2N2 by antigenic shift.[12] In August 2004, researchers in China found H5N1 in pigs.[13] Measured resistance to the standard antiviral drugs amantadine and rimantadine in H3N2 in humans has increased[14] to 92% in 2005.[15]

Chairul Nidom, a virologist at Airlangga University's tropical disease center in Surabaya, East Java, conducted an 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.[16][17]

Pathophysiology

Influenza viruses bind through hemagglutinin onto sialic acid sugars on the surfaces of epithelial cells; typically in the nose, throat and lungs of mammals and intestines of birds (Stage 1 in infection figure).[18]

Swine flu in humans

People who work with poultry and swine, especially people with intense exposures, are at increased risk of zoonotic infection with influenza virus endemic in these animals, and constitute a population of human hosts in which zoonosis and reassortment can co-occur.[19] Transmission of influenza from swine to humans who work with swine was documented in a small surveillance study performed in 2004 at the University of Iowa.[20] This study among others forms the basis of a recommendation that people whose jobs involve handling poultry and swine be the focus of increased public health surveillance.[19] The 2009 swine flu outbreak is an apparent reassortment of several strains of influenza A virus subtype H1N1, including a strain endemic in humans and two strains endemic in pigs, as well as an avian influenza.[21]

The US CDC reports that the symptoms and transmission of the swine flu from human to human is much like seasonal flu, commonly fever, lethargy, lack of appetite and coughing. Some people with swine flu also have reported runny nose, sore throat, nausea, vomiting and diarrhea.[22] It is believed to be spread between humans through coughing or sneezing of infected people and touching something with the virus on it and then touching their own nose or mouth.[23] Swine flu cannot be spread by pork products, since the virus is not transmitted through food.[23] The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days. Diagnosis can be made by sending a specimen, collected during the first five days, to the CDC for analysis.[24]

The swine flu is susceptible to four drugs licensed in the United States, amantadine, rimantadine, oseltamivir and zanamivir, however, for the 2009 outbreak it is recommended it be treated with oseltamivir and zanamivir.[25] The vaccine for the human seasonal H1N1 flu does not protect against the swine H1N1 flu, even if the virus strains are the same specific variety, as they are antigenically very different.[26]

Prevention

Recommendations to prevent infection by the virus consist of the standard personal precautions against influenza. This includes frequent washing of hands with soap and water or with alcohol-based hand sanitizers, especially after being out in-public. People should avoid touching their mouth, nose or eyes with their hands unless they've washed their hands. If people do cough, they should either cough into a tissue and throw it in the garbage immediately, cough into their elbow, or, if they cough in their hand, they should wash their hands immediately.[27]

Veterinary vaccines

Swine influenza has become a greater problem in recent decades as the evolution of the virus has resulted in inconsistent responses to traditional vaccines. Standard commercial swine flu vaccines are effective in controlling the infection when the virus strains match enough to have significant cross-protection, and custom (autogenous) vaccines made from the specific viruses isolated are created and used in the more difficult cases.[28][29]

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 nonreactive H3N2 SIV variants suggests that current commercial vaccines might not effectively protect pigs from infection with a majority of H3N2 viruses.[30][31]

Treatment

The CDC recommends the use of Tamiflu (oseltamivir) or Relenza (zanamivir) for the treatment and/or prevention of infection with swine influenza viruses. The virus isolates that have been tested from the US and Mexico are however resistant to amantadine and rimantadine.[32] If a person gets sick, antiviral drugs can make the illness milder and make the patient feel better faster. They may also prevent serious flu complications. For treatment, antiviral drugs work best if started soon after getting sick (within 2 days of symptoms).

Epidemiology

Outbreaks in swine

2007 Philippine outbreak

On August 20, 2007 Department of Agriculture officers investigated the outbreak of swine flu in Nueva Ecija and Central Luzon, Philippines. The mortality rate is less than 10% for swine flu, unless there are complications like hog cholera. On July 27, 2007, the Philippine National Meat Inspection Service (NMIS) raised a hog cholera "red alert" warning over Metro Manila and 5 regions of Luzon after the disease spread to backyard pig farms in Bulacan and Pampanga, even if these tested negative for the swine flu virus.[33][34]

Outbreaks in humans

1918 Influenza

Main article: 1918 flu pandemic

The "Spanish" influenza pandemic of 1918–1919 infected one third of the world's population (or ≈500 million persons at that time) and caused ≈50 million deaths.[35] In the U.S., approximately 675,000 people died of the disease.[36] The impact of this pandemic was not limited to 1918–1919. All influenza A pandemics since that time, and indeed almost all cases of influenza A worldwide (excepting human infections from avian viruses such as H5N1 and H7N7), have been caused by descendants of the 1918 virus, including "drifted" H1N1 viruses and reassorted H2N2 and H3N2 viruses. The latter are composed of key genes from the 1918 virus, updated by subsequently incorporated avian influenza genes that code for novel surface proteins, making the 1918 virus indeed the "mother" of all pandemics.[37]

Before and after 1918, most influenza pandemics developed in Asia and spread from there to the rest of the world. Confounding definite assignment of a geographic point of origin, the 1918 pandemic spread more or less simultaneously in 3 distinct waves during an ≈12-month period in 1918–1919, in Europe, Asia, and North America (the first wave was best described in the United States in March 1918).[38]

1976 U.S. outbreak

On February 5, 1976, an army recruit at Fort Dix said he felt tired and weak. He died the next day and four of his fellow soldiers were later hospitalized. Two weeks after his death, health officials announced that swine flu was the cause of death and that this strain of flu appeared to be closely related to the strain involved in the 1918 flu pandemic. Alarmed public-health officials decided that action must be taken to head off another major pandemic, and they urged President Gerald Ford that every person in the U.S. be vaccinated for the disease. The vaccination program was plagued by delays and public relations problems, but about 24% of the population had been vaccinated by the time the program was canceled.

About 500 cases of Guillain-Barré syndrome, resulting in death from severe pulmonary complications for 25 people, were probably caused by an immunopathological reaction to the 1976 vaccine. Other influenza vaccines have not been linked to Guillain-Barré syndrome, though caution is advised for certain individuals, particularly those with a history of GBS.[39][40]

2009 swine flu outbreak

Main article: 2009 swine flu outbreak
  Confirmed cases followed by death
  Confirmed cases
  Unconfirmed or suspected cases
See also: Live map of swineflu, H1N1 live map

The new strain of influenza involved in the 2009 swine flu outbreak strain is a reassortment of several strains of influenza A virus subtype H1N1 that are, separately, endemic in humans and in swine. Preliminary genetic characterization found that the hemagglutinin (HA) gene was similar to that of swine flu viruses present in U.S. pigs since 1999, but the neuraminidase (NA) and matrix protein (M) genes resembled versions present in European swine flu isolates. Viruses with this genetic makeup had not previously been found to be circulating in humans or pigs, but there is no formal national surveillance system to determine what viruses are circulating in pigs in the U.S.[14]

The origins of this new strain remain unknown. One theory is that Asian and European strains traveled to Mexico in migratory birds or in people, then combined with North American strains in Mexican pig factory farms before jumping over to farm workers.[41] The Mexican health agency acknowledged that the original disease vector of the virus may have been flies multiplying in manure lagoons of pig farms near Perote, Veracruz, owned by Granjas Carroll,[42] a subsidiary of Smithfield Foods.[43]

See also

References

Wikimedia Commons has media related to Swine flu.
  1. ^ Heinen PP (15 September 2003). "Swine influenza: a zoonosis". Veterinary Sciences Tomorrow. ISSN 1569-0830. Influenza B and C viruses are almost exclusively isolated from man, although influenza C virus has also been isolated from pigs and influenza B has recently been isolated from seals.
  2. ^ http://www.cnn.com/2009/HEALTH/04/25/swine.flu/index.html
  3. ^ a b c "Swine Influenza". Swine Diseases (Chest). Iowa State University College of Veterinary Medicine.
  4. ^ Shin JY, Song MS, Lee EH, Lee YM, Kim SY, Kim HK, Choi JK, Kim CJ, Webby RJ, Choi YK (2006). "Isolation and characterization of novel H3N1 swine influenza viruses from pigs with respiratory diseases in Korea". Journal of Clinical Microbiology. 44 (11): 3923–7. doi:10.1128/JCM.00904-06. PMID 16928961.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ Ma W, Vincent AL, Gramer MR, Brockwell CB, Lager KM, Janke BH, Gauger PC, Patnayak DP, Webby RJ, Richt JA (26 December 2007). "Identification of H2N3 influenza A viruses from swine in the United States". Proc Nat Acad Sci U S A. 104 (52): 20949–54. doi:10.1073/pnas.0710286104. PMC 2409247. PMID 18093945.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ Yassine HM, Al-Natour MQ, Lee CW, Saif YM (2007). "Interspecies and intraspecies transmission of triple reassortant H3N2 influenza A viruses". Virol J. 28 (4): 129. doi:10.1186/1743-422X-4-129. PMC 2228287. PMID 18045494. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
  7. ^ Heinen PP (15 September 2003). "Swine influenza: a zoonosis". Veterinary Sciences Tomorrow. ISSN 1569-0830. Influenza B and C viruses are almost exclusively isolated from man, although influenza C virus has also been isolated from pigs and influenza B has recently been isolated from seals.
  8. ^ Centers for Disease Control and Prevention > Key Facts about Swine Influenza (Swine Flu) Retrieved on April 27, 2009
  9. ^ Swine Flu and You, CDC, 2009-04-26, retrieved 2009-04-26
  10. ^ Yu, H. (2008). "Genetic evolution of swine influenza A (H3N2) viruses in China from 1970 to 2006". Journal of Clinical Microbiology. 46 (3): 1067. doi:10.1128/JCM.01257-07. PMID 18199784. {{cite journal}}: Unknown parameter |month= ignored (help)
  11. ^ "Bird flu and pandemic influenza: what are the risks?". UK Department of Health.
  12. ^ Lindstrom Stephen E, Cox Nancy J, Klimov Alexander (15 October 2004). "Genetic analysis of human H2N2 and early H3N2 influenza viruses, 1957–1972: evidence for genetic divergence and multiple reassortment events". Virology. 328 (1): 101–19. doi:10.1016/j.virol.2004.06.009. PMID 15380362.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  13. ^ World Health Organization (28 October 2005). "H5N1 avian influenza: timeline" (PDF).
  14. ^ a b "Swine influenza A (H1N1) infection in two children --- Southern California, March--April 2009". Morbidity and Mortality Weekly Report. Centers for Disease Control. 22 April 2009.
  15. ^ Advisory Committee on Immunization Practices (8 August 2008). "Prevention and Control of Influenza". MMWR. 57(RR07) (1–60). Centers for Disease Control.
  16. ^ "Indonesian pigs have avian flu virus; bird cases double in China". University of Minnesota: Center for Infectious Disease Research & Policy. 27 May 2005. Retrieved 2009-04-26.
  17. ^ Roos Robert, ed. (31 March 2009). "H5N1 virus may be adapting to pigs in Indonesia". University of Minnesota: Center for Infectious Disease Research & Policy. Retrieved 2009-04-26. report on pigs as carriers
  18. ^ Wagner, R (2002). "Functional balance between haemagglutinin and neuraminidase in influenza virus infections". 12 (3): 159–66. doi:10.1002/rmv.352. PMID 11987141. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |journapi9juuj9il= ignored (help); Unknown parameter |month= ignored (help)
  19. ^ a b Gray GC, Kayali G (2009). "Facing pandemic influenza threats: the importance of including poultry and swine workers in preparedness plans". Poultry Science. 88 (4): 880–4. doi:10.3382/ps.2008-00335. PMID 19276439. {{cite journal}}: Unknown parameter |month= ignored (help)
  20. ^ Gray GC, McCarthy T, Capuano AW, Setterquist SF, Olsen CW, Alavanja MC (2007). "Swine workers and swine influenza virus infections". Emerging Infectious Diseases. 13 (12): 1871–8. PMID 18258038. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  21. ^ "Deadly new flu virus in US and Mexico may go pandemic". New Scientist. 2009-04-24. Retrieved 2009-04-26.
  22. ^ "Q & A: Key facts about swine influenza (swine flu) - Symptoms". Centers for Disease Control and Prevention. 24 April 2009. Retrieved 2009-04-26.
  23. ^ a b "Q & A: Key facts about swine influenza (swine flu) – Spread of Swine Flu". Centers for Disease Control and Prevention. 24 April 2009. Retrieved 2009-04-26.
  24. ^ "Q & A: Key facts about swine influenza (swine flu) – Diagnosis". Centers for Disease Control and Prevention. 24 April 2009. Retrieved 2009-04-26.
  25. ^ "Q & A: Key facts about swine influenza (swine flu) – Treatment". Centers for Disease Control and Prevention. 2009-04-24. Retrieved 2009-04-26.
  26. ^ "Q & A: Key facts about swine influenza (swine flu) – Virus Strains". Centers for Disease Control and Prevention. 24 April 2009. Retrieved 2009-04-26.
  27. ^ "CDC - Influenza (Flu) | Swine Influenza (Flu) Investigation". Cdc.gov. Retrieved 2009-04-27.
  28. ^ "Swine flu virus turns endemic". National Hog Farmer. 15 September 2007.
  29. ^ "Swine". Custom Vaccines. Novartis.
  30. ^ Gramer Marie René, Lee Jee Hoon, Choi Young Ki, Goyal Sagar M, Joo Han Soo (July 2007). "Serologic and genetic characterization of North American H3N2 swine influenza A viruses". Canadian Journal of Veterinary Research. 71 (3): 201–206. PMID 1899866.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  31. ^ Myers KP, Olsen CW, Gray GC (2007). "Cases of swine influenza in humans: a review of the literature". Clin Infect Dis. 44 (8): 1084–8. doi:10.1086/512813. PMC 1973337. PMID 17366454. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  32. ^ "Antiviral Drugs and Swine Influenza". Centers for Disease Control. Retrieved 2009-04-27.
  33. ^ "DA probes reported swine flu 'outbreak' in N. Ecija". Gmanews.tv. Retrieved 2009-04-25.
  34. ^ "Gov't declares hog cholera alert in Luzon". Gmanews.tv. Retrieved 2009-04-25.
  35. ^ [http://www.cdc.gov/ncidod/eid/vol12no01/05-0979.htm#1/ Frost WH. Statistics of influenza morbidity. Public Health Rep. 1920;35:584–97
  36. ^ Pandemics and Pandemic Threats since 1900. U.S. Department of Health & Human Services
  37. ^ Taubenberger JK, Morens DM (2006). "1918 Influenza: the mother of all pandemics". Emerg Infect Dis. 12 (1). Centers for Disease Control and Prevention (CDC). {{cite journal}}: Unknown parameter |month= ignored (help)
  38. ^ [http://www.cdc.gov/ncidod/eid/vol12no01/05-0979.htm#whe/ 1918 Influenza: the Mother of All Pandemics
  39. ^ Haber P, Sejvar J, Mikaeloff Y, Destefano F (2009). "Vaccines and guillain-barré syndrome". Drug Saf. 32 (4): 309–23. doi:10.2165/00002018-200932040-00005. PMID 19388722. {{cite journal}}: Unknown parameter |doi_brokendate= ignored (|doi-broken-date= suggested) (help)CS1 maint: multiple names: authors list (link)
  40. ^ "Influenza / Flu Vaccine". University of Illinois at Springfield. Retrieved 26 April 2009.
  41. ^ David Kirby, [http://www.huffingtonpost.com/david-kirby/swine-flu-outbreak----nat_b_191408.html Swine Flu Outbreak – Nature Biting Back at Industrial Animal Production?], The Huffington Post, 26 April 2009
  42. ^ [http://www.jornada.unam.mx/2009/04/06/index.php?section=estados&article=030n1est Granjas Carroll provocó la epidemia de males respiratorios en Perote, según agente municipal], La Jornada, 5 April 2009. Template:Es icon
  43. ^ "Swine-flu outbreak could be linked to Smithfield factory farms, by Tom Philpott". Grist.org, 25 April 2009. Retrieved 2009-04-27.

Further reading

Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Swine_influenza&oldid=286521558"