Content on this page was developed during the 2009-2010 H1N1 pandemic and has not been updated. The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide.

The English language content on this website is being archived for historic and reference purposes only.

For current, updated information on seasonal flu, including information about H1N1, see the CDC Seasonal Flu website.

CDC Estimates of 2009 H1N1 Influenza Cases, Hospitalizations and Deaths in the United States

During the pandemic, CDC provided estimates of the numbers of 2009 H1N1 cases, hospitalizations and deaths on seven different occasions. Final estimates were published in 2011. These final estimates were that from April 12, 2009 to April 10, 2010 approximately 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (195,086-402,719), and 12,469 deaths (8868-18,306) occurred in the United States due to pH1N1. These final estimates are available at: Estimating the burden of 2009 pandemic influenza A (H1N1) in the United States (April 2009-April 2010), Shrestha SS, et al., Clin Infect Dis. 2011 Jan 1;52 Suppl 1:S75-82.

Below are links to the different estimates published, including the final estimates.

April – October 17, 2009 Estimates

April – November 14, 2009 Estimates

April – December 12, 2009 Estimates

April 2009 – January 16, 2010 Estimates

April 2009 – February 13, 2010 Estimates

April 2009 – March 13, 2010 Estimates

Final Estimates Published in May 2011