2009 swine flu pandemic

Cases of this strain of influenza by country

Country	Laboratory confirmed cases	Other possible cases*	Deaths from all cases*
Mexico	20	1400+	86
United States	20	100+	0
Canada	6	5	0
New Zealand	0	25+	0
Colombia	0	12	0
Spain	0	8	0
United Kingdom	0	6	0
France	0	4	0
Brazil	0	2	0
Israel	0	1	0
Total	46	1563+	86
(*) 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.

The 2009 H1N1 influenza outbreak is the spread of a new strain of 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 cases are characterized by severe influenza-like symptoms, followed by pneumonia, which has been fatal in some Mexican cases.

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. In April both the WHO and the U.S. Centers for Disease Control (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.

On April 25, 2009, 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". Government health agencies around the world also expressed concerns over the outbreak and are monitoring the situation closely.

Train commuters in Mexico City wearing surgical masks.

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. Up to April 8, 2009, the USA Centers for Disease Control and Prevention (CDC) had reported the deaths of 43 children from seasonal flu, compared to 68 in the previous flu season. The improvement was attributed in part to an improved northern hemisphere 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.

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

New influenza outbreak

  Confirmed deaths.

  Confirmed cases.

  Unconfirmed or suspected cases.

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. The surge was assumed by Mexican authorities to be "late-season flu" (which usually coincides with a mild Influenzavirus B peak) until April 21, when a CDC alert concerning two isolated cases of a novel swine flu was reported in the media. 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. This new strain was promptly confirmed in Mexico, connecting the new strain to the ongoing outbreak of ILI. 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 81 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; 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. The Mexican fatalities are mainly young adults of 25 to 45, a hallmark of pandemic flu. 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. 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."

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 A virus subtype H1N1, and swine influenza virus typically found in Asia and Europe - "an unusually mongrelised mix of genetic sequences." 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).

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. The seasonal influenza strain H1N1 vaccine is thought to be unlikely to provide protection.

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". 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.

According to Mike Stobbe of the Associated Press:

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

Canada

See also: National Responses: Canada

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

Nova Scotia's chief medical officer, Dr. Robert Strang, said Sunday the National Microbiology Laboratory in Winnipeg confirmed late Saturday, April 25, that four young people in the province are recovering from "relatively mild" cases of the disease. The four all attend King's-Edgehill School preparatory school in Windsor, which held a school trip to the Yucatan Peninsula.

B.C.'s Centre for Disease Control on Sunday confirmed two cases of swine flu involving two people from the province who recently returned from Mexico.

Mexico

Mexican police officers with masks on to protect themselves from the swine flu strain.

Mexican officials stated that since March 2009, there have been over 1300 reported cases 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.

United States

Main article: 2009 H1N1 flu outbreak in the 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. 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. 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. One case has been confirmed in Ohio. 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.

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

Pandemic concern

See also: Pandemic Severity Index

A graphical representation of the CDC's Pandemic Severity Index. (This index is unrelated to the six WHO pandemic phases of an influenza pandemic)

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

New strain

The virus is a new strain of influenza, from which human populations have not been vaccinated or naturally immunized.

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. 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.

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.

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.

Other points

Some 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.

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. Current development, large-scale manufacturing, distribution and delivery of a new vaccine takes several months.

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) and zanamivir (Relenza) but resistant to amantadine and remantadine.

Tamiflu and Relenza also have a preventative effect against Influenzavirus A.

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". 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.

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".

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.

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.

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. 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. (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.)

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".

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. In the USA, two confirmed cases were detected through their "border infectious disease surveillance".

Asia

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. 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.

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

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. Japanese Agriculture Minister Shigeru Ishiba appeared on television to reassure customers that it was safe to eat pork. 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.

South Korea warned against travel to Mexico City and three Mexican states. 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.

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. The Philippines may quarantine travelers arriving from Mexico with fevers. 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.

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.

According to the Malaysian Health Ministry, health screenings will be carried out on passengers traveling to and from Mexico begining on April 17. 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.

Europe

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

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.

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

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. Three patients who had just returned from Mexico were under observation in in multiple regions of Spain.

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

Serbia on Saturday banned all imports of pork from North America, despite reassurances from the FAO that pigs appear not to be the immediate source of infection.

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.

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. On April 26 after undergoing testing, Northwick Park Hospital confirmed the crew member did not have the swine flu.

On April 26, two people were admitted to Monklands Hospital in Scotland with mild flu-like symptoms after returning from Mexico, and four people were given medication and advised to stay in their home in Northamptonshire, again after returning from Mexico with flu-like symptoms. 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.

North America

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. 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. 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.

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. 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 out 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. 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." In both provinces, the cases either involved people who had recently returned from Mexico or those in close contact with them.

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.

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

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. 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. 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. On April 25, President Felipe Calderón declared an emergency which granted him the power to suspend public events and order quarantines. Hours later, Córdova announced classes will be officially suspended through May 6.

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."

South America

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.

The Minister of Social Protection, Diego Palacio, 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.

Oceania

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.

See also

CDC conference with the media on the swine flu outbreak on April 25, 2009

• 1918 flu pandemic
• Avian flu
• Hong Kong Flu (1968-1969), killed an estimated one million people worldwide.
• Severe acute respiratory syndrome (SARS)
• Other medical disasters

External links

• Swine influenza, at the World Health Organization
• WHO's Pandemic Influenza Phases
• BioHealthBase Bioinformatics Resource Center Database of influenza genomic sequences and related information.
• Global map of reported H1N1 outbreaks in 2009
• H1N1 outbreak timeline

USA Centers for Disease Control (CDC)

• Swine Influenza (Flu) portal
  • Human Swine Influenza Investigation
  • Interim Guidance on Case Definitions for Swine Influenza A (H1N1) Human Case Investigations for state and local health department investigations
  • RSS feed
• Video podcast
• @CDCemergency twitter account

European Centre for Disease Prevention and Control (ECDC)

• Threat Assessment for Swine Influenza at 19:00 hours 24th April 09
• Information with Daily Update
  • Swine Influenza FAQs

Popular forums

• Twitter #swineflu search