Questions & Answers

2009 H1N1 Flu In The News

January 15, 2010 1:00 PM ET

How many 2009 H1N1 cases, hospitalizations and deaths are estimated to have occurred in the United States?

CDC developed a method to provide an estimated range of the total number of 2009 H1N1 cases, hospitalizations and deaths in the United States by age group using data on flu associated hospitalizations collected through CDC’s Emerging Infections Program. On November 12, 2009 CDC provided the first estimates for April through October 17, 2009 and committed to updating those estimates approximately monthly. On December 10, 2009, CDC issued updated estimates for the numbers of 2009 H1N1 cases, hospitalizations and deaths in the United States since the pandemic started in April 2009 through November 14, 2009. On January 15, 2010, CDC again issued updated estimates of the number of 2009 H1N1 cases, hospitalizations and deaths for the United States from April 2009 through December 12, 2009.

• CDC estimates that between 39 million and 80 million cases of 2009 H1N1 occurred between April and December 12, 2009. The mid-level in this range is about 55 million people infected with 2009 H1N1.

• CDC estimates that between about 173,000 and 362,000 2009 H1N1-related hospitalizations occurred between April and December 12, 2009. The mid-level in this range is about 246,000 H1N1-related hospitalizations.

• CDC estimates that between about 7,880 and 16,460 2009 H1N1-related deaths occurred between April and December 12, 2009. The mid-level in this range is about 11,160 H1N1-related deaths.

The latest estimates released on January 15, 2010 incorporate an additional 4 weeks of flu data (from November 15, 2009 through December 12, 2009) from the previous estimates released on December 10, 2009. The latest estimates through December 12 show a modest increase in the total number of 2009 H1N1 cases, hospitalizations and deaths since the 2009 H1N1 virus emerged. The previous estimates of 2009 H1N1 cases, hospitalizations and deaths through November 14 encompassed the peak of 2009 H1N1 activity in the United States.

A table showing this data by age group is available. In addition, background information on these estimates and information about the methodology used to generate these estimates also is available on the CDC web site.