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2009 swine flu pandemic

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The outbreak of a new strain of influenza virus in March and April of 2009 is infecting many people in Mexico City, other regions of Mexico, and parts of the United States. In Mexico, in some cases it causes severe influenza-like illness, followed by pneumonia, which furthermore has in some cases resulted in death. The new strain is derived in part from human influenzavirus A (subtype H1N1), and in part from several strains of influenza virus usually found only in swines (see Swine flu). In April both the World Health Organization (WHO) and the U.S. Centers for Disease Control (CDC)[1] expressed serious concerns that this novel strain, which apparently transmits from human-to-human and which to date appears to have a relatively high mortality rate in Mexico, has the potential to become a flu pandemic. Government health agencies around the world, including the European Centre for Disease Prevention and Control (ECDC), the UK Health Protection Agency and the Public Health Agency of Canada, have also expressed concerns over the outbreak and are monitoring the situation closely.

Cases of this strain of influenza by country or state.
Country or State Confirmed laboratory cases Other possible cases* Deaths from all cases*
Mexico 18[2] 1300+[3] 81[4]
New York 8[5] 200[5] 0
California 7[6] 0 0
Texas 3[6] 0 0
Kansas 2[6] 0 0
United Kingdom 0 1[7] 0
Total 37 1500+ 81
(*) Not all cases have been confirmed as due to this strain. Possible cases are cases of influenza-like illness (ILI) that have not been confirmed through testing to be due to this strain.

Background of outbreak

Train commuters in Mexico City wearing surgical masks.

The outbreak was first detected in the Federal District of Mexico, where surveillance began picking up cases of ILI starting 18 March.[8] The first two cases identified as swine flu were two children living in San Diego County and Imperial County, California, who became ill on March 28 and 30.[9] A CDC alert concerning these two isolated cases was reported in the media on April 21.[10] The story of the outbreak was broadcast live first in Mexico on April 23, 2009.

In March and April 2009, over 1000 cases of suspected swine flu in humans were detected in Mexico and the southwestern United States. The strain was unusually virulent in Mexico, causing more than 60 deaths, mostly in Mexico City and central Mexico;[3] In the United States, virulence apparently was below average. Some cases in Mexico and the United States have been confirmed by the World Health Organization to be a never-before-seen strain of H1N1.[8][2] The Mexican fatalities are mainly young adults, a hallmark of pandemic flu.[11] A new swine flu strain has been confirmed in 16 of the deaths and at least 100 others are being tested as of April 24, 2009.[12] Mexican Health Minister José Ángel Córdoba on April 24, said "We’re dealing with a new flu virus that constitutes a respiratory epidemic that so far is controllable."[3]

On 25th April 2009, the World Health Organization agreed that the current situation constitutes a public health emergency of international concern.[13]

Genetics and effects

Influenza (flu)
H1N1 virus
Types
Vaccines
Treatment
Pandemics
Outbreaks
See also

Anne Schuchat, director of CDC's National Center for Immunization and Respiratory Diseases, 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, human influenza A virus subtype H1N1, and swine influenza virus typically found in Asia and Europe - "an unusually mongrelised mix of genetic sequences."[14] For two cases a complete genome sequence had been obtained. This complete genome is presently being worked with by U.S. scientists to prepare it for transition to become a vaccine. She said that the virus was resistant to amantadine and rimantadine, but susceptible to oseltamivir (Tamiflu) and zanamivir (Relenza).[15][16][17][18] 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.[19] The seasonal influenza strain H1N1 vaccine is thought to be unlikely to provide protection.[20]

In an interview on April 24, acting CDC director Dr. Richard Bessar said that it was still not understood why the American cases were primarily mild disease while the Mexican cases had led to multiple deaths. Differences in the viruses or co-infection were being considered. Only fourteen samples from Mexico had been tested by the CDC, with seven found to match the American strain, and the CDC was still in discussions with Mexico about plans to send an American investigative team. He said that the virus had likely passed through several cycles of infection with no known linkages between patients in Texas and California, and that containment of the virus is "not very likely".[21][22]

Countries affected

Mexico

Mexican officials state that since March 2009, there have been over 1000 reported cases and put the death toll at 81, with 20 confirmed to be linked to a new swine influenza strain of Influenza A virus subtype H1N1.[23][24][25]

United States

Main article: 2009 H1N1 flu outbreak in the United States

Officials in the United States said that eight people were infected with swine flu in California and Texas and all have recovered.[26] Eight school children in New York City are believed to be infected after a school trip to Mexico. The New York case has been confirmed as Influenza A Virus, which meets the Centers for Disease Control and Prevention (or CDC) definition of a probable case of swine flu. Tests are still underway to determine if this flu virus is the new strain of H1N1. Two cases have been confirmed in Kansas. Kansas state health officials confirmed the two cases as swine flu on April 25th 2009, just minutes after New York health officials said they had eight probable cases.

Pandemic concern

The U.S. Centers for Disease Control and the World Health Organization are concerned that this outbreak may become a pandemic, because:[27]

  • The virus is a new strain of influenza, from which human populations have not been vaccinated or naturally immunized.[28]
  • The virus has produced severe disease in Mexico, and some deaths. Furthermore, in Mexico (but not in the United States) the illness has primarily struck young, healthy adults, much like the deadly Spanish Flu of 1918. This is unlike most influenza strains which produce the worst symptoms in young children, elderly adults, and others with weaker immune systems.[29][2]
  • The virus appears to infect by human-to-human transmission. Investigations of infected patients indicate no direct contact with swine, such as at a farm or agricultural fair.[2] In contrast, for example, disease transmission in the last severe human outbreak of influenza, the bird flu that peaked in 2006, was determined to be entirely or almost entirely from direct contact between humans and birds.[30]
  • The virus has been detected in multiple regions within Mexico and multiple areas in the United States.

Response

Canada

Dr. Michael Gardam, director of infectious disease prevention and control at Ontario's public health agency, said in an interview with the CBC that an outbreak of swine flu in Ontario, Canada's most populous province, would not be as serious as the 2003 SARS epidemic.[31] In preparing for and dealing with influenza pandemic, the Public Health Agency of Canada follows the WHO's categories, but has expanded them somewhat.[32] Despite initial reports of two swine influenza cases in a Montreal hospital, an official on the Montreal regional health board confirmed negative results for all quarantined patients at the hospital and that no quarantines were currently in effect at the hospital.[33] Canadian laboratories assisted the Mexican government in confirming their eighteen confirmed cases.[2]

Denmark

Kåre Mølbak, department manager at Statens Serum Institut under the Danish Ministry of Health and Prevention, said the agency monitors developments in Mexico and are already able to identify the virus if any Danes should have been unfortunate enough to have become infected on a trip to Mexico. Hospitals have also been notified and instructed in what signs to look for.[34]

Ireland

Head of Health Protection with the HSE Dr Kevin Kelleher said: “The ECDC and the World Health Organisation has confirmed that no cases of this illness have occurred in Europe, but that we should continue to closely follow the emerging situation.”[35]

Mexico

Mexican soldiers distributing protective masks to citizens.

On April 24, 2009, schools (from pre-school to university level) as well as libraries, museums, concerts, and any public gathering place, were shut down by the government in Mexico City and the neighbouring State of Mexico to prevent the disease from spreading further; the schools in Mexico City, the State of Mexico, and the state of San Luis Potosí will remain closed through at least 5 May.[36] Marcelo Ebrard, Mexico City's mayor, has also asked all night-life operators to shut down their places for ten days to prevent further infections.[37] José Ángel Córdoba, federal Secretary of Health, said on April 24 that schools will probably be suspended for at least the following week, and that it will take around ten days to see the evolution of the virus' behavior, and to consider other measures after such.[38] On April 25, President Felipe Calderón declared an emergency which granted him the power to suspend public events and order quarantines.[39]

Philippines

The Secretary of the Department of Agriculture of the Philippines issued an order banning the importation of hogs from the U.S. and Mexico, and the retraction of the restriction of swine influenza vaccine use.[40]

Peru

In response to the outbreak, Alex Kouri, governor of Callao, announced that the Callao Regional Government took precautionary steps to prevent entry of the virus by declaring a state of maximum air and sea alert.[41]

United Kingdom

The Health Protection Agency said on 24 April: "No cases of swine flu have been identified in the UK or anywhere in Europe. The reported events in the US and Mexico are unusual and warrant further investigation and vigilance on the part of other countries. More investigation and testing is needed to determine the severity of the disease and the ease with which it can spread."[42]

On 25 April 2009, a British Airways member of the cabin crew of British Airways flight number BA242 was taken to hospital and quarantined after falling ill with "flu-like symptoms" on a flight from Mexico City to Heathrow.[43] The man, who was not named, was taken to Northwick Park Hospital in Harrow for further testing and treatment under quarantine .

United Nations

The United Nations agency saw no need at this point to issue travel advisories warning travellers not to go to parts of Mexico or the United States. The spokesperson said that the situation might change "depending on what the situation in the field is".[44] WHO Director-General Margaret Chan also said that it was too premature to issue such recommendations without better analysis and understanding of the situation at this stage.[45]

United States

An official for the White House said, "The White House is taking the situation seriously and monitoring for any new developments. The president has been fully briefed." [46] Gov. Arnold Schwarzenegger and the state of California activated the Joint Emergency Operations Center of the Department of Public Health, and are coordinating with the California Emergency Management Agency, the CDC, and the Mexican government. They have additionally stepped up other preparations to lessen the flu's threat.[47]

World Health Organization

The World Health Organization (WHO) said in a statement "Because there are human cases associated with an animal influenza virus, and because of the geographical spread of multiple community outbreaks, plus the somewhat unusual age groups affected, these events are of high concern" and "WHO acknowledges the United States and Mexico for their proactive reporting and their collaboration with WHO and will continue to work with Member States to further characterize the outbreak".[2]

The WHO has established an Emergency Committee for emergency discussions to assess the situation and to formulate appropriate responses. The first meeting of the committee was held on 25 April in Geneva. [13] The WHO is highly concerned on the cases of swine influenza and expressed that all countries should intensify surveillance for unusual outbreaks of influenza-like illness and severe pneumonia. [13]

Before the first meeting, WHO Director-General Margaret Chan said that the Emergency Committee could make recommendations including whether to change the pandemic alert level or not.[44][48] The WHO stated that the viruses obtained from the human cases with swine influenza in the United States were sensitive to oseltamivir (Tamiflu)[49] and zanamivir (Relenza) but resistant to amantadine and remantadine. [50]

See also

References

  1. ^ "CDC Press Briefing Transcripts April 24, 2009". Cdc.gov. 2009-01-23. Retrieved 2009-04-25.
  2. ^ a b c d e f "Influenza-Like Illness in the United States and Mexico". World Health Organization. 2009-04-24. Retrieved 2009-04-25.
  3. ^ a b c Lacey, Marc (April 24, 2009). "Fighting Deadly Flu, Mexico Shuts Schools". The New York Times. {{cite news}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ Reuters. Swine flu may have killed up to 81 in Mexico. (April 25, 2009).
  5. ^ a b "Up to 200 possibly infected with swine flu at Queens high school". New York Times. 2009-04-26. Retrieved 2009-04-25.
  6. ^ a b c Dobnik, Verena (2009-04-25). "2 swine flus in Kan., US total 11; 8 likely in NY". Associated Press. Retrieved 2009-04-25.
  7. ^ "Cabin crew member in hospital after flight from swine flu-struck Mexico". The Guardian . 2009-04-25. Retrieved 2009-04-25.
  8. ^ a b "Q&A: Swine flu". BBC News.
  9. ^ David Brown (April 22, 2009). "New Strain of Swine Flu Investigated: Two Children in San Diego Area Had No Contact with Pigs". Washington Post. Retrieved April 24, 2009.
  10. ^ Mike Stobbe (April 21, 2009). "Officials alert doctors after 2 California children infected with unusual swine flu". Associated Press. Retrieved April 24, 2009.
  11. ^ "Deadly new flu virus in US and Mexico may go pandemic", New Scientist, April 24, 2009
  12. ^ "Experts probe deadly Mexico flu". BBC News. 2009-04-24. Retrieved 2009-04-25.
  13. ^ a b c http://www.who.int/mediacentre/news/statements/2009/h1n1_20090425/en/index.html "Swine influenza". WHO. 2009-04-25.
  14. ^ http://www.newscientist.com/article/dn17025-deadly-new-flu-virus-in-us-and-mexico-may-go-pandemic.html
  15. ^ Steven Reinberg (2009-04-24). "Swine Flu Cases Now Total 7: CDC". ABC News.
  16. ^ Rob Stein (2009-04-23). "In California and Texas, 5 New Swine Flu Cases". Washington Post.
  17. ^ "CDC Briefing on Public Health Investigation of Human Cases of Swine Influenza". CDC online newsroom. 2009-04-23.
  18. ^ "Influenza-like illness in the United States and Mexico". WHO. 2009-04-24.
  19. ^ "Swine Influenza A (H1N1) Infection in Two Children --- Southern California, March--April 2009". CDC MMWR. 2009-04-22.
  20. ^ "Update: Swine Influenza A (H1N1) Infections --- California and Texas, April 2009". CDC MMWR. 2009-04-24.
  21. ^ "CDC Briefing on Public Health Investigation Reuters of Human Cases of Swine Influenza (transcript)". CDC. 2009-04-24.
  22. ^ "CDC says too late to contain U.S. flu outbreak". Reuters. 2009-04-24.
  23. ^ "Q&A: Swine flu". BBC News.
  24. ^ "CDC: Swine flu viruses in U.S. and Mexico match". {{cite web}}: Text "publisher:CNN" ignored (help)
  25. ^ "Influenza-Like Illness in the United States and Mexico". World Health Organization.
  26. ^ "Human Swine Influenza Investigation". US Centers for Disease Control (CDC).
  27. ^ Besser, Richard, Acting Director CDC. CDC Press Transcript April 24, 2009 (unedited): "there are really three things we want to look for when we’re thinking about whether a virus is causing a new pandemic...".
  28. ^ U.S. Centers for Disease Control. Morbidity and Mortality Weekly Report Dispatch, April 21, 2009.
  29. ^ Stein, Rob and Brown, David. Washington Post (April 25, 2009). Swine Flu Found in Mexican Outbreak
  30. ^ Global spread of H5N1
  31. ^ "Swine flu not as serious as SARS: Canada's Ontario".
  32. ^ Public Health Agency of Canada: The Canadian Pandemic Influenza Plan for the Health Sector
  33. ^ "Swine-flu fears at Lakeshore General unfounded". The Gazette (Montreal). 2009-04-25. Retrieved 2009-04-25.
  34. ^ http://www.dr.dk/Nyheder/Udland/2009/04/25/161845.htm
  35. ^ Irish Times: Irish authorities issue swine flu warning
  36. ^ "AP Top News at 9:11 p.m. EDT". Associated Press. 2009-04-25. Retrieved 2009-04-25.
  37. ^ [Pide Ebrard parar 10 días vida nocturna "Estima SSA 10 dias de alerta por influenza"]. Reforma. 2009-04-25. {{cite web}}: Check |url= value (help)
  38. ^ "Estima SSA 10 dias de alerta por influenza". El Universal. 2009-04-25.
  39. ^ "Mexico's Calderon Declares Emergency Amid Swine Flu Outbreak". Bloomberg. 2009-04-25.
  40. ^ "RP bans pork, hogs from US, Mexico". ABS-CBN. 2009-04-26. Retrieved 2009-04-26.
  41. ^ "Peru: Callao on maximum alert over swine flu". Living In Peru. 2009-04-25. Retrieved 2009-04-25. {{cite web}}: |first= missing |last= (help)
  42. ^ http://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1240646410227 Health Protection Agency ]
  43. ^ Cabin crew member in hospital after flight from swine flu-struck Mexico
  44. ^ a b "WHO ready with antivirals to combat swine flu". Reuters. 2009-04-24.
  45. ^ "Virtual press briefing - swine influenza (25 April 2009)". WHO.
  46. ^ "White House closely following U.S. swine flu outbreak".
  47. ^ "Gov. Schwarzenegger Directs State Swine Flu Response". 2009-04-24. Retrieved 2009-04-25.
  48. ^ "WHO calls emergency meeting on swine flu".
  49. ^ "WHO Says Initial Findings Show Swine Flu Responds To Tamiflu". Nasdaq.com. Retrieved 2009-04-25.
  50. ^ "Swine influenza questions and answers" (PDF). WHO.
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