influenza pandemic (H1N1) of 2009

Introduction
Symptoms and transmission
Early stages of the outbreak
Pandemic status and response
The H1N1 virus
Treatment and prevention

References & Edit History Quick Facts & Related Topics

Images

influenza pandemic (H1N1) of 2009; Sebelius, Kathleen

Kathleen Sebelius addressing the media about the federal response to the spread of the swine flu (influenza A[H1N1]) virus, April 28, 2009.

Kathleen Sebelius being briefed on the swine flu (influenza A[H1N1]) epidemic by Deputy National Security Adviser John Brennan, April 28, 2009.

Infographic bar graph comparing U.S. death tolls from major events, with COVID-19 at over 1.1 million deaths, the Civil War and 1918-19 flu pandemic each above 675,000, and smaller bars for wars, pandemics, and disasters such as World War II, the Vietnam War, and September 11.

Quizzes

Warm water fuels Hurricane Katrina. This image depicts a 3-day average of actual dea surface temperatures for the Caribbean Sea and Atlantic Ocean, from August 25-27, 2005.

Disasters of Historic Proportion

Related Questions

How are strains of H1N1 different from one another?
How did acquired immunity help reduce H1N1 outbreaks after the pandemic?
How did single-dose H1N1 vaccines change vaccination efforts during the pandemic?
How did the 2009 H1N1 outbreak spread from Mexico to other countries?
How did the death toll of the 2009 H1N1 pandemic compare with the 1918–19 influenza pandemic?
How does antigenic shift increase the risk of an influenza pandemic?
How many H1N1 illnesses and hospitalizations did the CDC estimate occurred in the United States?
How many countries had been affected by H1N1 by mid-January 2010?
How was the 2009 H1N1 virus transmitted between people?
How was the Pandemrix vaccine linked to narcolepsy cases in some countries?
What did a level 5 H1N1 pandemic alert mean in April 2009?
What did a level 6 pandemic alert mean during the 2009 H1N1 outbreak?
What did the World Health Organization declare on April 25, 2009?
What genetic material did the 2009 H1N1 virus contain?
What symptoms were common in people infected with the 2009 H1N1 virus?
When did clinical trials of a 2009 H1N1 vaccine begin?
When did the World Health Organization declare that the 2009 H1N1 pandemic had ended?
Which antiviral drugs were used to treat H1N1 infection in 2009?
Which countries reported H1N1 cases soon after the outbreak began in Mexico?
Which countries were targeted for donated H1N1 vaccine doses through the World Health Organization?
Which people faced the greatest risk of severe illness from 2009 H1N1 infection?
Which severe symptoms could occur during H1N1 infection?
Who was identified as the first known H1N1 case in La Gloria, Mexico?
Why are pigs thought to play a role in the emergence of new influenza A viruses?
Why did H1N1 activity increase in the United States during autumn 2009?
Why did confirmed H1N1 case and death totals underestimate the pandemic's true impact?
Why did the 2009 H1N1 virus spread around the world so quickly?
Why did the CDC change its method for estimating H1N1 cases and deaths in the United States?
Why did the World Health Organization declare H1N1 a pandemic on June 11, 2009?
Why is the exact origin of the 2009 H1N1 virus uncertain?

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External Websites

World Health Organisation - Pandemic (H1N1) 2009
World Health Organisation - What is the pandemic (H1N1) 2009 virus?
Centers for Disease Control and Prevention - Pandemic (H1N1) 2009 Influenza

influenza pandemic (H1N1) of 2009

Also known as: H1N1 flu, swine flu

Written by

Kara Rogers

Kara Rogers is the senior editor of biomedical sciences at Encyclopædia Britannica, where she oversees a range of content from medicine and genetics to microorganisms. She joined Britannica in 2006 and...

Kara Rogers

Fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

History

influenza pandemic (H1N1) of 2009, the first major influenza outbreak in the 21st century, noted for its rapid global spread, which was facilitated by an unusually high degree of viral contagiousness. Global dissemination of the virus was further expedited by the unprecedented rates of passenger travel that characterize the modern era. The pandemic virus caused a respiratory disease typical of that resulting from infection with seasonal influenza. However, despite local, national, and international efforts to...