Swine flu outbreak threatens pandemic

The 2009 swine flu outbreak is the spread of a new strain of H1N1 influenza virus that began in March of 2009. Localized outbreaks of influenza-like illness (ILI) were detected in three areas initially in Mexico and soon after in the United States. Following the discovery of the new strain in the United States, its presence was quickly confirmed in multiple nations across several continents. There have been over 1,600 suspected cases. Because it is not possible to confirm every one of such cases as being caused by an influenza virus, the World Health Organization (WHO) refers to them collectively as influenza-like illnesses (ILI)

The new strain is derived in part from human influenzavirus A (subtype H1N1), and in part from two strains of swine influenza as well as an avian influenza.[19] In April both the WHO and the United States Centers for Disease Control and Prevention (CDC) expressed serious concerns about this novel strain, because it apparently transmits from human to human, has had a relatively high mortality rate in Mexico, and because it has the potential to become a flu pandemic.[20]

On April 25, 2009, the WHO determined the situation to be a formal "public health emergency of international concern", with knowledge lacking in regard to "the clinical features, epidemiology, and virology of reported cases and the appropriate responses".[21] Government health agencies around the world also expressed concerns over the outbreak and are monitoring the situation closely.

As of April 26, 2009, Mexico City Schools remained closed[22] while dozens of other schools and school districts in the US closed due to confirmed cases in students.[23][24] It is feared many US schools will be forced to close within upcoming weeks to prevent the spread of the flu.[25]
Background of outbreak

Prior influenza season

Prior to the outbreak, the Northern Hemisphere winter of 2008-2009 had been a comparatively mild season for flu infections, which typically cause 250,000-500,000 deaths yearly, mostly in the elderly, the very young, and persons with chronic illness.[26] Up to April 8, 2009, the CDC had reported the deaths of 43 children from seasonal flu, compared to 68 in the previous flu season.[27] The improvement was attributed in part to an improved Northern Hemisphere winter of 2008-2009 seasonal flu vaccine, for which a rare decision had been made to update all three strains (H1, H3, and B) simultaneously, which ultimately yielded a very good match to the strains of H1N1 and H3N2 which eventually circulated. (This followed the poor performance of the 2007-2008 vaccine, which offered only 2-20% protection rather than the 70-90% achieved in some years.) The improvement was also attributed to new recommendations including the vaccination of 5-18 year olds, who potentially act as "super-spreaders" due to failure to take precautions such as hand-washing.[28][29]

Furthermore, from December 2005 through February 2009, a total of twelve human infections with swine influenza were reported from ten states in the USA.[30]

Recent influenza outbreak

The outbreak was first detected in the Federal District of Mexico, where surveillance began picking up a surge in cases of ILI starting March 18.[31] The surge was assumed by Mexican authorities to be "late-season flu" (which usually coincides with a mild Influenzavirus B peak[32]) until April 21,[33][34] when a CDC alert concerning two isolated cases of a novel swine flu was reported in the media.[35] The first two cases identified (and confirmed) as swine flu were two children living in the United States, in San Diego County and Imperial County, California, who became ill on March 28 and 30.[36] This new strain was promptly confirmed in Mexico, connecting the new strain to the ongoing outbreak of ILI. The first deadly case seems to go back to the 13th April, some samples being sent to the US based CDC the 18th.[37] News of the connection was broadcast live 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 88 confirmed deaths so far, mostly in Mexico City, but there have also been cases reported in the states of San Luis Potosí, Hidalgo, Querétaro and Mexico State, all in central Mexico;[3] 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.[31][38] The Mexican fatalities are mainly young adults of 25 to 45, a hallmark of pandemic flu.[39][40] A new swine flu strain was confirmed in 16 of the deaths and at least 100 others were being tested as of April 24, 2009.[41] Mexican Health Minister José Ángel Córdova on April 24, said "We're dealing with a new flu virus that constitutes a respiratory epidemic that so far is controllable."[3]

The origins of the new virus 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.[42] The Mexican health agency acknowledged that the original carrier of the virus may have been flies multiplying in manure lagoons of pig farms near Perote, Veracruz, owned by Granjas Carroll,[43] a subsidiary of Smithfield Foods.[44]

Genetics and effects

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, human influenza, and swine influenza virus typically found in Asia and Europe - "an unusually mongrelised mix of genetic sequences."[45] Pigs have been shown to act as a potential "mixing vessel" in which reassortment can occur between flu viruses of several species.[46][47] 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 because their genome is packaged in 8 pieces (see Orthomyxoviridae).

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. Director Schuchat said that the virus was resistant to amantadine and rimantadine, but susceptible to oseltamivir (Tamiflu) and zanamivir (Relenza).[48][49][50][51]

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. While viruses with this genetic makeup had not previously been found to be circulating in humans or pigs, there is no formal national surveillance system to determine what viruses are circulating in pigs in the U.S.[52] The seasonal influenza strain H1N1 vaccine is thought to be unlikely to provide protection.[53]

In an interview on April 24, acting CDC director 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. 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".[54][55] The U.S. embassy reported that a CDC investigative team had arrived in Mexico City on April 25 to work with Mexican counterparts to study the virus.[33]

According to Mike Stobbe of the Associated Press:[56]

A big question is: Just how deadly is the virus in Mexico? The seasonal flu tends to kill just a fraction of 1 percent of those infected. In Mexico, about 70 deaths out of roughly 1,000 cases represents a fatality rate of about 7 percent. The Spanish flu pandemic of 1918-19, which killed an estimated 50 million worldwide, had a fatality rate of about 2.5 percent. The Mexican rate sounds terrifying. But it's possible that far more than 1,000 people have been infected with the virus and that many had few if any symptoms, said Dr. Michael Osterholm, a prominent pandemic expert at the University of Minnesota. U.S. health officials echoed him.

Confirmed cases

Currently, only the Canadian National Microbiology Laboratory (NML) in Winnipeg, Manitoba, and the U.S. Centers for Disease Control and Prevention (CDC) headquarters in Atlanta, Georgia, have developed the reagents necessary to positively identify the A/09(H1N1) swine influenza. Other countries with suspected cases, such as Mexico, have laboratories that can rule out the strain by negative identification (confirmation of another testable strain), but have to send a sample to the NML or CDC to confirm any case.[32]


Four cases of swine flu have been confirmed in Nova Scotia and two in British Columbia.[8]

Nova Scotia's chief medical officer, Dr. Robert Strang, said on 26 April that the National Microbiology Laboratory in Winnipeg confirmed late the previous day, that four young people in the province were recovering from "relatively mild" cases of the disease. The four all attended King's-Edgehill School preparatory school in Windsor; and one of the four infected students had been on a recent school trip to the Yucatan Peninsula.[8][57]

The British Columbia Centre for Disease Control on 26 April confirmed two cases of swine flu involving two people from the province who recently returned from Mexico.


Dr. Jose A. Cordova Villalobos, Mexico's Secretary of Health stated that since March 2009, there have been over 1300 reported cases[58] and put the death toll at 83, with 20 confirmed to be linked to a new swine influenza strain of Influenza A virus subtype H1N1.[59][60][61]

United States

Officials in the United States confirmed that seven people in California, two students from a high school in Texas, and a married couple in Kansas were infected with the A/09(H1N1) swine flu; all have recovered.[62] One additional student from the same high school in Texas is suspected of probably having the influenza strain. New York now has confirmed cases of swine flu.[63] The cases in Kansas and New York are linked to travel to Mexico; most of the cases in California and Texas are not linked and may reflect localized outbreaks of this virus in those areas.[64] One case has been confirmed in Ohio.[5] A public health emergency has been declared, but it was said that this is standard procedure in cases as divergent as the recent inauguration and flooding.[65]

Cases in the USA have been less severe than in Mexico, with no deaths and only one of the eight confirmed cases hospitalized.[66]

Pandemic concern

The U.S. Centers for Disease Control and the World Health Organization are concerned that this outbreak may become a pandemic, because:[67]
New strain The virus is a new strain of influenza, from which human populations have not been vaccinated or naturally immunized.[68]Human transmission 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.[38] 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 almost entirely from direct contact between humans and birds.[69]Virulence 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. Most other influenza strains produce the worst symptoms in young children, elderly adults, and others with weaker immune systems.[70][38]Geography The virus has been detected in multiple areas across North America, with other possible cases reported in Europe, the Middle East, South America, and the South Pacific. This indicates that containment is unlikely.[66][39]Other pointsSome other specificities which are also important to rate, such as the contagiousness setting the percentage of a population susceptible to this virus, are data which are not yet known.

Prevention and treatment

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 or, if they cough in their hand, they should wash their hands immediately.[71]

The previously recommended influenza vaccines for the southern and northern hemispheres, including that for the 2009/2010 flu season, are ineffective against the new strain.[72] Current development, large-scale manufacturing, distribution and delivery of a new vaccine takes several months.[66]

US based medical product company Baxter International has requested a virus sample from the WHO in order to begin development of a new vaccine.[73] Baxter has patented a cell-based technology that may allow the company to develop a vaccine in half the time it usually takes, possibly cutting development time from six months to three.[74]

Of the available antiviral treatments for influenza, the WHO stated that the viruses obtained from the human cases with swine influenza in the United States were sensitive to oseltamivir (Tamiflu)[75] and zanamivir (Relenza) but resistant to amantadine and remantadine.[76]

Tamiflu and Relenza also have a preventative effect against Influenzavirus A.[77] Roche and the US government have extended the shelf-life of stock-piled Tamiflu from the original five years to seven years because studies indicated that the medication continues to maintain its effectiveness.[78]

Some physicians in the US are recommending the use of masks when in public.[79] The purpose of a face mask is to effectively cover a person's mouth and nose so that if a person is around someone who is infected, there is a decreased likelihood of transmission. Recommendations to protect against the avian flu indicated that using a face mask with a rating of N99, N100 or P100 in the United States or a rating of FFP3 in Europe should be effective in protecting against transmission.[80] While face masks with these ratings provide 99% or greater efficiency in protecting against flu transmission, N95 or FFP2 face masks provide about 94% efficiency. N95 and FFP2 rated face masks may therefore also be effective.[81]

UN World Health Organization

The World Health Organization (WHO) 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".[82] 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.[83]

In a statement, the WHO said "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".[38]

The WHO 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 April 25 in Geneva.[21]

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.[82][84]

The WHO decided not to raise the level of the worldwide pandemic alert after the first meeting, which remains at Phase 3 on the six-point scale.[85] A Phase 3 alert means that a new virus has been confirmed but there is no or limited evidence of human-to-human transmission -insufficient to sustain community-level outbreaks. The Phase 3 alert was initially set due to the avian flu.[86][87][88] (Phase 4, "Sustained Human to Human Transmission," entails community-wide outbreaks; Phases 5/6, "Widespread Human Infection," entails human-to-human transmission in at least two counties in one WHO region; Phase 6 is a global pandemic proper.)[89]

The Emergency Committee "identified a number of gaps in knowledge about the clinical features, epidemiology, and virology of reported cases and the appropriate responses", and on its advice, the WHO advised "that all countries intensify surveillance for unusual outbreaks of influenza-like illness and severe pneumonia".[21]

National responses

Many countries confirmed that inbound international passengers will be screened. Typical airport health screening involves asking passengers which countries they have visited and checking whether they feel or look particularly unwell. Thermographic equipment was put into use at a number of airports to screen passengers. In the USA, two confirmed cases were detected through their "border infectious disease surveillance".[66] A number of countries advised against travel to known affected regions.


The General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) of China issued an emergency notice on the evening of 26 April that visitors returning from flu-affected areas who experienced flu-like symptoms within two weeks would be quarantined.[90] The Ministry of Health has started prevention measures and initiated cooperation with the WHO and the relevant departments of the governments of Mexico and the U.S. to help contain the outbreak. According to Wang Jing of the China Inspection and Quarantine Science Research Institute, the measures already in place in China against bird flu are sufficient for this new disease.[91]

Hong Kong and Taiwan said visitors who came back from affected areas with fevers would be quarantined.[92]

The Ministry of Agriculture, Forestry and Fisheries of Japan instructed animal quarantine offices across Japan to examine any live pigs to be brought into Japan to make sure they are not infected with the influenza.[93] Japanese Agriculture Minister Shigeru Ishiba appeared on television to reassure customers that it was safe to eat pork.[92] The Japanese farm ministry said that it would not ask for restrictions on pork imports because the virus was unlikely to turn up in pork, and would be killed by cooking.[94]

South Korea warned against travel to Mexico City and three Mexican states.[92] The government has also stepped up quarantine and safety checks on travellers arriving from the United States and Mexico, and pork imports from those countries. An emergency quarantine system is also in place, with simple tests conducted on people arriving with flu symptoms at airports.[90]

Philippines' Health Secretary Francisco T. Duque III has ordered the Bureau of Quarantine to use thermal imaging equipment at airports to screen passengers coming from the US for flu symptoms.[95] The Philippines may quarantine travelers arriving from Mexico with fevers.[96] Also, 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.[97]

Singapore's minister of health Khaw Boon Wan urged citizens to limit travel to affected areas such as Mexico and the United States. The health ministry advised the public to seek immediate medical attention if they experienced symptoms within seven days after arriving from affected areas, to maintain good hygiene, and for those sick with respiratory illness to avoid crowded areas and wear masks.[94]

According to the Malaysian Health Ministry, health screenings will be carried out on passengers traveling to and from Mexico begining on April 17.[98] The Health Ministry's disease control division has activated its operations room to monitor the swine flu situation and informed medical practitioners who are treating cases with symptoms of influenza-like illness or severe pneumonia and persons had visited Mexico, California or Texas, to inform the district health office immediately for preventive and control measures.[99]


In France, possible cases of swine flu were being investigated in four people who had recently visited Mexico. Other tested cases had proved negative.[16]

The Netherlands National Institute for Public Health and the Environment advised any traveller who returned from Mexico since April 17 and developed a fever of 38.5 degrees Celsius (101.3 degrees Fahrenheit) within four days of arriving in the Netherlands to stay at home.[96]

The Polish Foreign Ministry issued a statement recommending that citizens avoid travel to affected areas until the outbreak is totally contained.[96]

AENA, the Spanish state owned company who manages all Spanish airports and Air Traffic Control established a protocol for the flights coming from and to Spain from the affected areas.[100] Three patients who had just returned from Mexico were under observation in in multiple regions of Spain.[101]

Russia banned the import of meat products from Mexico, California, Texas and Kansas.[2]

Serbia on Saturday banned all imports of pork from North America, despite reassurances from the FAO (Food and Agriculture Organization of United Nations) that pigs appear not to be the immediate source of infection.[2]

Italy's agriculture lobby, Coldiretti, warned against panic reaction, noting that farmers lost hundreds of millions of euros (dollars) because of consumers boycotts during the 2001 mad cow scare and the 2005 bird flu outbreak.[2]

United Kingdom

On April 25, 2009, a member of the cabin crew of British Airways flight number BA242 was taken to Northwick Park Hospital in Harrow and quarantined after falling ill with "flu-like symptoms" on a flight from Mexico City to Heathrow.[102] On April 26 after undergoing testing, Northwick Park Hospital confirmed the crew member did not have the swine flu.[103]

On April 26, two people were admitted to Monklands Hospital in Scotland with mild flu-like symptoms after returning from Mexico,[104] and four people were given medication and advised to stay in their home in Northamptonshire, again after returning from Mexico with flu-like symptoms.[15] In both cases the symptoms were said to be mild. On the same date, passengers were held on planes arriving at Heathrow, from Mexico City, whilst officials carried out health checks.[105]

North America


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.[106] In preparing for and dealing with an influenza pandemic, the Public Health Agency of Canada follows the WHO's categories, but has expanded them somewhat.[107] 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.[108]

On April 26, the Government of Nova Scotia announced, on a live webcast, that four students in Windsor, Nova Scotia have confirmed cases of swine flu.[109] Later that day, the Federal Government confirmed the existence of a total of six cases in Canada; four in Nova Scotia and two in British Columbia. Health minister Leona Aglukkaq said the Canadian federal government would take whatever measures were necessary to keep the public safe, and that as Canada continued to ramp up its surveillance efforts there would likely be more reported cases. She also said she had been in contact with her provincial and territorial counterparts and had ordered the Public Health Agency of Canada to alert border authories, quarantine officers and other officials.[110] However, Canada's Chief Public Health Officer, Dr. David Butler-Jones, stated that the six affected Canadians suffered from only mild symptoms and have already started to recover. Butler-Jones warned against complacency though, stating that the fact that only mild cases have been reported so far "doesn't mean we won't see either some more severe illness or potentially deaths."[111] In both provinces, the cases either involved people who had recently returned from Mexico or those in close contact with them.[112]

The two cases in British Columbia involved two young men aged 25-35 from the B.C. lower mainland who had recently come back from Mexico, according to Dr. Danuta Skowronski, head of flu and respiratory illnesses at the B.C. Centre for Disease Control, run by the provincial government. The cases were discovered by normal flu testing conducted by the disease control center after the men had visited a doctor about flu-like symptoms. Skowronski said the two men have been asked to 'self-isolate' themselves but have not officially been quarantined. He noted the disease seemed 'widespread' in Mexico and should not be mistaken by tourists to be linked only with urban Mexico City.[113] The National Microbiology Laboratory in Winnipeg confirmed on Sunday, April 26 that four students at King's-Edgehill School in Windsor, a small town in Nova Scotia's Annapolis Valley, have a mild case of swine flu. Nova Scotia's chief public health officer, Dr. Robert Strang, said the four students are between the ages of 12 and 18 and were already recovering. Only one of the students had been on a trip to Mexico's Yucatan Peninsula according to Joe Seagram, the headmaster of the private school.[114]

Canadian laboratories assisted the Mexican government in confirming their eighteen confirmed cases.[38]

Two cases in Saskatchewan are currently under investigation.[115]


Soldiers mobilized by the Mexican government have handed out six million surgical masks to citizens in and around Mexico City.[116] 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 neighboring 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.[117] 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.[118] José Ángel Córdova, federal Secretary of Health, said on April 24 that schools will probably be suspended for at least the following week then, and that it will take around ten days to see the evolution of the virus' behavior, and to consider other measures after such.[119] On April 25, President Felipe Calderón declared an emergency which granted him the power to suspend public events and order quarantines.[120] Hours later, Córdova announced classes will be officially suspended through May 6.[121]

On 26 April, the World Bank announced US$ 25 million in immediate aid loans to Mexico, an additional US$ 180 million for long-term assistance to address the outbreak, and advice on how other nations have responded to similar crises[116]

United States

The United States of America has declared a state of Public Health Emergency. According to the New York Times, "the emergency declaration frees resources to be used toward diagnosing or preventing additional cases and releases money for more antiviral drugs," including the transfer of approximately 12 million influenza medications from a federal stockpile to states.[116][122] The U.S. plans to follow a guidebook developed over the past five years to fight a pandemic flu, such as H5N1.

South America


All passengers arriving to the country from Mexico and United States must fill out a form to be located in case they show symptoms of flu according to an Epidemic Alert order issued by The Ministry of Health.[123]


The Health Ministry reported that three people suspected of being infected with swine flu are under observation in the Coyhaique Regional Hospital, the Carlos Van Buren Hospital in Valparaíso and the Hospital del Tórax in Santiago. The Health minister Alvaro Erazo stated that two of the cases have initially tested negative to exams, indicating they are likely not infected, while a third case is under study. Regarding the Chivas de Guadalajara football team, slated to arrive back in Chile from Mexico, the minister stated they will undergo examination as will other passengers.[124]


The Minister of Social Protection, Diego Palacio (in Spanish), announced on April 26, 2009 that 12 suspect cases have been detected, 9 in Bogotá and 3 on the Caribbean coast. Samples of the virus have been sent to the USA for comparisons and analysis and confirmation should be expected in a couple of days.[12]


The Governor of Callao, Alex Kouri ordered that all passengers from any infected country, mainly Mexico and USA, must be checked before their arrival on peruvian territory. Also, any case or syntom of fever must be warned to the peruvian government. This in order to prevent any infections, since the main port and airport of Peru are located on Callao. Also, the government has prepared and especial area for any case of this disease on the Hospital "Daniel Alcides Carrión".[125]


New Zealand

Following a three-week language trip to Mexico, ten students from Rangitoto College, a secondary school in North Shore City, Auckland, exhibited influenza symptoms. All 22 students and three accompanying teachers from the trip are currently in home isolation, with oseltamivir provided to the patients and those in contact with them. 10 students have tested positive for an influenza A virus; further testing is needed to confirm A/09 (H1N1) infection.


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