2009 swine flu pandemic

The 2009 swine flu pandemic, caused by the H1N1/swine flu/influenza virus and declared by the World Health Organization (WHO) from June 2009 to August 2010, was the third recent flu pandemic involving the H1N1 virus (the first being the 1918–1920 Spanish flu pandemic and the second being the 1977 Russian flu). The first identified human case was in La Gloria, Mexico, a rural town in Veracruz. The virus appeared to be a new strain of H1N1 that resulted from a previous triple reassortment of bird, swine, and human flu viruses which further combined with a Eurasian pig flu virus, leading to the term "swine flu".

Unlike most strains of influenza, the pandemic H1N1/09 virus did not disproportionately infect adults older than 60 years; this was an unusual and characteristic feature of the H1N1 pandemic. Even in the case of previously healthy people, a small percentage develop pneumonia or acute respiratory distress syndrome (ARDS). This manifests itself as increased breathing difficulty and typically occurs three to six days after initial onset of flu symptoms. The pneumonia caused by flu can be either direct viral pneumonia or a secondary bacterial pneumonia. A November 2009 New England Journal of Medicine article recommended that flu patients whose chest X-ray indicates pneumonia receive both antivirals and antibiotics. In particular, it is a warning sign if a child seems to be getting better and then relapses with high fever, as this relapse may be bacterial pneumonia.

Some studies estimated that the real number of cases including asymptomatic and mild cases could be 700 million to 1.4 billion people—or 11% to 21% of the global population of 6.8 billion at the time. The lower value of 700 million is more than the 500 million people estimated to have been infected by the Spanish flu pandemic. However, the Spanish flu infected approximately a third of the world population at the time, a much higher proportion.

The number of lab-confirmed deaths reported to the WHO is 18,449 and is widely considered a gross underestimate. The WHO collaborated with the US Centers for Disease Control and Prevention (CDC) and Netherlands Institute for Health Services Research (NIVEL) to produce two independent estimates of the influenza deaths that occurred during the global pandemic using two distinct methodologies. The 2009 H1N1 flu pandemic is estimated to have actually caused about 284,000 (range from 150,000 to 575,000) excess deaths by the WHO-USCDC study and 148,000–249,000 excess respiratory deaths by the WHO-NIVEL study. A study done in September 2010 showed that the risk of serious illness resulting from the 2009 H1N1 flu was no higher than that of the yearly seasonal flu. For comparison, the WHO estimates that 250,000 to 500,000 people die of seasonal flu annually. However, the H1N1 influenza epidemic in 2009 resulted in a large increase in the number of new cases of narcolepsy.

Name

The World Health Organization uses the term "(H1N1) 2009 pandemic" when referring to the event, and officially adopted the name "A(H1N1)pdm09" for the virus in 2010, after the conclusion of the pandemic.

Controversy arose early on regarding the wide assortment of terms used by journalists, academics, and officials. Labels like "H1N1 flu", "Swine flu", "Mexican flu", and variations thereof were typical. Criticism centered on how these names may confuse or mislead the public. It was argued that the names were overly technical (e.g. "H1N1"), incorrectly implying that the disease is caused by contact with pigs or pig products, or provoking stigmatization against certain communities (e.g. "Mexican"). Some academics of the time asserted there is nothing wrong with such names, while research published years later (in 2013) concluded that Mexican Americans and Latino Americans had indeed been stigmatized due to the frequent use of term "Mexican flu" in the news media.

Official entities adopted terms with varying consistency over the course of the pandemic. The CDC used names like "novel influenza A (H1N1)" or "2009 H1N1 flu". The Netherlands National Institute for Public Health and the Environment used the term "Pig Flu" early on. Officials in Taiwan suggested use of the names "H1N1 flu" or "new flu". The World Organisation for Animal Health, an IGO based in Europe, proposed the name "North American influenza". The European Commission adopted the term "novel flu virus". Officials in Israel and South Korea briefly considered adoption of the name "Mexican virus" due to concern about the use of the word "swine". In Israel, objections stemmed from sensitivity to religious restrictions on eating pork in the Jewish and Muslim populations, in South Korea, concerns were influenced by the importance of pork and domestic pigs.

As terminology changed to deal with these and other such issues, further criticism was made that the situation was unnecessarily confusing. For example, the news department at the journal Science produced an article with the humorous title "Swine Flu Names Evolving Faster Than Swine Flu Itself".

History

Analysis of the genetic divergence of the virus in samples from different cases indicated that the virus jumped to humans in 2008, probably after June, and not later than the end of November, likely around September 2008. The research also indicated the virus had been latent in pigs for several months prior to the outbreak, suggesting a need to increase agricultural surveillance to prevent future outbreaks. In 2009, U.S. agricultural officials speculated, although emphasizing that there was no way to prove their hypothesis, that "contrary to the popular assumption that the new swine flu pandemic arose on factory farms in Mexico, [the virus] most likely emerged in pigs in Asia, but then traveled to North America in a human." However, a subsequent report by researchers at the Mount Sinai School of Medicine in 2016 found that the 2009 H1N1 virus likely originated from pigs in a very small region of central Mexico.

Initially called an "outbreak", widespread H1N1 infection was first recognized in the state of Veracruz, Mexico, with evidence that the virus had been present for months before it was officially called an "epidemic". The Mexican government closed most of Mexico City's public and private facilities in an attempt to contain the spread of the virus; however, it continued to spread globally, and clinics in some areas were overwhelmed by infected people. The new virus was first isolated in late April by American and Canadian laboratories from samples taken from people with flu in Mexico, Southern California, and Texas. Soon the earliest known human case was traced to a case from 9 March 2009 in a 5-year-old boy in La Gloria, Mexico, a rural town in Veracruz. In late April, the World Health Organization (WHO) declared its first ever "public health emergency of international concern", or PHEIC, and in June, the WHO and the U.S. CDC stopped counting cases and declared the outbreak a pandemic.

Despite being informally called "swine flu", the H1N1 flu virus cannot be spread by eating pork products; similar to other influenza viruses, it is typically contracted by person to person transmission through respiratory droplets. Symptoms usually last 4–6 days. Antivirals (oseltamivir or zanamivir) were recommended for those with more severe symptoms or those in an at-risk group.

The pandemic began to taper off in November 2009, and by May 2010, the number of cases was in steep decline. On 10 August 2010, the Director-General of the WHO, Margaret Chan, announced the end of the H1N1 pandemic and announced that the H1N1 influenza event had moved into the post-pandemic period. According to WHO statistics (as of July 2010), the virus had killed more than 18,000 people since it appeared in April 2009; however, they state that the total mortality (including deaths unconfirmed or unreported) from the H1N1 strain is "unquestionably higher". Critics claimed the WHO had exaggerated the danger, spreading "fear and confusion" rather than "immediate information". The WHO began an investigation to determine whether it had "frightened people unnecessarily". A flu follow-up study done in September 2010, found that "the risk of most serious complications was not elevated in adults or children." In a 5 August 2011 PLOS ONE article, researchers estimated that the 2009 H1N1 global infection rate was 11% to 21%, lower than what was previously expected. However, by 2012, research showed that as many as 579,000 people could have been killed by the disease, as only those fatalities confirmed by laboratory testing were included in the original number, and meant that many without access to health facilities went uncounted. The majority of these deaths occurred in Africa and Southeast Asia. Experts, including the WHO, have agreed that an estimated 284,500 people were killed by the disease, much higher than the initial death toll.