The CDC reports 500 deaths from influenza. (Table 10 of http://www.cdc.gov/nchs/data/dvs/deaths_2010_release.pdf)
The CDC reports flu-associated deaths ranging from from a low of about 3,000 to a high of about 49,000 people.
The CDC says:
It has been recognized for many years that influenza is infrequently listed on death certificates and testing for seasonal influenza infections is usually not done, particularly among the elderly who are at greatest risk of seasonal influenza complications and death. Some deaths — particularly in the elderly — are associated with secondary complications of seasonal influenza (including bacterial pneumonias).
Thompson et al. review the CDC's methodology.
Because a broad range of respiratory and cardiac diagnoses have been associated with influenza virus infections and these infections are often not confirmed by virologic testing, statistical models based on vital statistics data have been used for decades to estimate the overall burden of influenza in the United States.
In general, the estimates from each of these models suggest that seasonal influenza epidemics from 1976 through 2000 were associated with substantial morbidity, including >200,000 annual hospitalizations and an annual average of >30,000 influenza-associated all-cause US deaths.
They review the range of statistical models that have been used to estimate the mortality caused by influenza.
The report mentions:
- a linear-regression approach,
- Serfling-type models, using Poisson regression techniques, and
- simpler models, based on rate differences, [that] have been used for many years to estimate influenza-associated morbidity and mortality.
In my opinion, the CDC is making a sincere attempt to accurately estimate the number of deaths attributable to influenza.
I could find no evidence that the CDC is intentionally over-reporting annual flu deaths.
Thompson, William W. and Comanor, Lorraine and Shay, David K., Epidemiology of Seasonal Influenza: Use of Surveillance Data and Statistical Models to Estimate the Burden of Disease J Infect Dis. (2006) 194 (Supplement 2): S82-S91 doi:10.1086/507558