Last week I talked about some H1N1 numbers from the CDC. The numbers I highlighted were by and large from either the CDC's focused surveillance sites, or based on reports voluntarily submitted by various hospitals, providers, etc.  Carl Zimmer has highlighted the CDC's effort to estimate the big picture - total infections, hospitalizations, and deaths nationwide. At this point, the CDC says there has been no seasonal flu - almost all flu cases have been H1N1.

Here is the estimate of the big H1N1 picture from April to mid-November:

• CDC estimates that between 34 million and 67 million cases of 2009 H1N1 occurred between April and November 14, 2009. The mid-level in this range is about 47 million people infected with 2009 H1N1.

• CDC estimates that between about 154,000 and 303,000 2009 H1N1-related hospitalizations occurred between April and November 14, 2009. The mid-level in this range is about 213,000 H1N1-related hospitalizations.

• CDC estimates that between about 7,070 and 13,930 2009 H1N1-related deaths occurred between April and November 14, 2009. The mid-level in this range is about 9,820 2009 H1N1-related deaths.

The updated estimates show an increase of about 2.5 times the number of cases, hospitalizations and deaths over the first estimates. This increase in the estimates correlates with a four week period of elevated and widespread flu activity in the United States. During this four-week period, influenza-like-illness (ILI) peaked nationally at 7.7 percent during the week ending October 24; continued at 7.5 percent for the week ending October 31; was 6.6 percent for the week ending November 7, 2009 and was 5.3% for the week ending November 14, 2009. The number of states reporting widespread activity was high throughout this time also, with 48 states continuing to report widespread activity from October 24 through November 7, and 43 states reporting widespread activity for the week ending November 14, 2009. Throughout this four week period, flu-associated hospitalizations and deaths were elevated as well. The increases in the latest estimates of cases, hospitalizations and deaths reflect the intense levels of activity that were occurring in the United States between October 18, 2009 and November 14, 2009.

In addition, the data continues to confirm previous findings that this disease primarily affects people younger than 65 years old, with the number of cases, hospitalizations and deaths overwhelmingly occurring in people 64 years and younger. The risk of illness, hospitalization and death related to 2009 H1N1 is very age specific and very different from seasonal influenza. With seasonal influenza, about 60 percent of seasonal flu-related hospitalizations and 90 percent of flu-related deaths occur in people 65 years and older. The proportion of younger people being impacted by 2009 H1N1 is much greater than what occurs during seasonal flu and their risk of serious illness, including hospitalization and death from 2009 H1N1 is much greater than that for seasonal flu. People 65 and older are much less affected by this virus than what routinely occurs with seasonal influenza and therefore the risk of serious illness, hospitalization and death from 2009 H1N1 in people in this age group is much less than that posed by seasonal flu.

The CDC offers some comparisons with seasonal flu: 
- Seasonal flu causes an average of 200,000 hospitalizations per year, with 60% of those occurring in those 65 and older. With H1N1, only about 10% of the hospitalizations have been for patients over 65.

- Seasonal flu causes about 36,000 deaths per year on average, with 90% of those occurring in people over 65.

The upside of H1N1 primarily affecting those under 65 is that there are fewer deaths compared with seasonal flu: taking the H1N1 mid-level estimates, there have been ~10,000 deaths for ~213,000 hospitalizations, compared with an average of 36,000 deaths and 200,000 hospitalizations for seasonal flu.

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