2009 swine flu pandemic

A 2009 Mexico and U.S. swine influenza outbreak of an Influenza A virus subtype H1N1 flu which the World Health Organisation has categorized as an ILI (Influenza Like Illness); the strain had an especially high mortality rate in the Mexican cases.

People riding a train in Mexico City wearing masks to protect themselves from receiving swine flu.

Outbreak

In March and April 2009, over 1,000 cases of unusually virulent flu in humans were detected in Mexico and the southwestern United States, causing more than 60 deaths, all in Mexico. Some of these have been confirmed by the World Health Organization to be a never-before-seen strain of H1N1. The story of the outbreak was broadcast live first in Mexico on April 23 2009 at around 23h. A new swine flu strain has been confirmed in 16 of the deaths and 44 others are being tested as of 24 April 2009. The Mexican fatalities are mainly young adults, a hallmark of pandemic flu.

Mexican Health Minister José Ángel Córdoba on April 24th, said "We’re dealing with a new flu virus that constitutes a respiratory epidemic that so far is controllable."

The first two cases detected in the US were two children living in San Diego County and Imperial County, who became ill on March 28 and 30. A CDC alert concerning these two isolated cases was reported in the media on April 21. As of April 24 eight human cases were known, including six in Southern California and two in Texas. The patients have recovered. The acting director of the US Centers for Disease Control (CDC) said that preliminary tests on 7 out of 14 samples from patients in Mexico had matched the virus found in the US, which experts say is a new strain of swine flu. None of the US patients had any contact with pigs, leading CDC officials to believe that human-to-human transmission has been occurring.

On April 24th, New York City health department dispatched a team of investigators to the private St. Francis Preparatory School in Queens after 75 students complained of symptoms consistent with the disease. Several of the students had recently traveled to Mexico.

Pandemic concern

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

• The virus is a new strain of influenza, from which human populations have not been vaccinated or naturally immunized.
• The virus has produced severe disease in Mexico, and some deaths. Furthermore, the illness has primarily struck young, healthy adults, much like the Spanish Flu of 1918 that killed millions, and unlike most influenza which produces graver symptoms in young children, elderly adults, and others with weaker immune systems.
• The virus appears to infect by human-to-human transmission, and has spread within Mexico and into the United States. 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 outbreak of influenza, the bird flu that peaked in 2006–2007, was determined to be almost entirely from direct contact with birds.

Response

International organizations

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".

The WHO will convene a meeting of its Emergency Committee on international health regulations for emergency discussions. WHO Director-General Margaret Chan said that the emergency committee could make recommendations including whether to change the pandemic alert level or not.

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".

Mexico

On April 24, 2009, schools (from pre-school to university level) as well as libraries, museums and any public gathering place, were shut down by the government in Mexico City and neighbouring State of Mexico to prevent the disease from spreading further. Mexico's 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.

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."

Canada

Dr. Michael Gardam, director of infectious disease prevention and control at Ontario's public health agency, said in an interview with the Canadian Broadcasting Corporation that an outbreak of swine flu in Ontario, Canada's most populous province, would not be as serious as the 2003 SARS epidemic.

Genetics and effects

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. For two cases a complete genome sequence had been obtained. She 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. 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. The seasonal influenza strain H1N1 vaccine is thought to be unlikely to provide protection.

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 fatalities. 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".

See also

• Flu
• 1918 flu
• Swine influenza
• Swine influenza 1976 U.S. outbreak
• H1N1
• Avian flu
• H5N1