The Swine Flu Pandemic of 2009

The 2009 flu pandemic is a global outbreak of a new strain of an influenza A virus subtype H1N1, referred to as the novel H1N1, first identified in April 2009, and commonly called swine flu. It is thought to be a reassortment of four known strains of influenza A virus: one endemic in (normally infecting) humans, one endemic in birds, and two endemic in pigs (swine). Transmission of the new strain is human-to-human, with cooked pork products safe to eat as the virus cannot be transmitted by eating foods.

The outbreak began in Mexico, with evidence that Mexico was already in the midst of an epidemic for months before the outbreak was recognized. Soon after, its government closed down most of Mexico City's public and private offices and facilities to help contain the spread. In early June, as the virus spread globally, the World Health Organization (WHO) declared the outbreak to be a pandemic, but also noted that most illnesses were of moderate severity. The virus later spread to the Southern Hemisphere which entered its winter flu season. Because the virus was spreading with unprecedented speed, many clinics were overwhelmed testing and treating patients, and WHO and the CDC stopped reporting all cases while focusing more on large outbreaks.

The virus spreads via coughing, sneezing or touching contaminated surfaces and then touching the nose or mouth. Symptoms, which last up to a week, are similar to those of seasonal flu, and can include fever, sneezes, sore throat, coughs, headache, and muscle or joint pains. The U.S. Centers for Disease Control and Prevention (CDC) noted that although this was a very serious virus, cases worldwide were usually mild, and most hospitalizations and deaths had been of persons that also had underlying conditions such as asthma, diabetes, obesity, heart disease, or a weakened immune system.

To prevent spreading the infection, the CDC recommends that those with symptoms stay home from school, work and crowded settings. Wearing facial masks is of "limited benefit" as they are designed for industrial workplace use and do not filter out viral or other biological agents. A number of countries in Asia have also quarantined airline passengers with flu symptoms to slow its spread. A vaccine to help prevent infection will become available this fall, but will first be given to healthcare workers, pregnant women, and other higher risk groups. One injection is still required for the "seasonal flu" and early tests indicate that only one injection will likewise be needed for swine flu.