The World Health Organization on March 11 declared the COVID-19 outbreak a pandemic, the first such declaration in 11 years.
Here's a look back on the 2009 swine flu pandemic with eight key facts from the CDC:
1. The flu strain responsible for the outbreak — influenza A (H1N1)pdm09 — was first detected in America in April 2009.
2. The strain represented a unique combination of influenza viruses never before seen in humans or animals.
3. The virus quickly spread globally, primarily affecting children and adults under 65 who lacked immunity to H1N1.
4. The WHO declared the swine flu outbreak a pandemic on June 11, 2009.
5. Between April 12, 2009, and April 10, 2010, the CDC estimates swine flu caused 60.8 million illnesses, 273,304 hospitalizations and 12,469 deaths in the U.S.
6. On Oct. 5, 2009, the U.S. began administering a newly approved H1N1 vaccine to select Americans, with vaccination coverage expanding nationwide by that December.
7. WHO declared an end to the pandemic on Aug. 10, 2010.
8. Globally, an estimated 151,700 to 575,400 people died from swine flu in the first year of the pandemic.
For reference, the COVID-19 pandemic has sickened 1,323 Americans and killed 38, as of March 12. More than 127,00 cases and 4,700 deaths have been reported globally.