Sunday, April 26, 2009

US Government Estimates for Influenza Pandemic

Now that everyone is thinking about the possibility of a swine flue pandemic, how bad could it get?

For educated estimates of the morbidity and mortality that the US could experience during an influenza pandemic, we can turn to the HHS Pandemic Influenza Plan, November 2005. This government plan was specifically avian influenza (H5N1) and not the swine flu virus (H1N1), but of course avian influenza remains a threat too, and the characteristics of a new virus are not predictable. The HHS plan provides the following estimates and bounds for the US, based on the statistics of three 20th century pandemics:

  • Number of ill: 90 million (30% of population)
  • Number requiring outpatient medical care: 45 million (45%-50% of the ill)
  • Number hospitalized: 0.865 million - 9.9 million
  • Number of deaths: 209,000 - 1,903,000

Estimates vary with the assumed severity of the disease, with the lesser numbers corresponding to a disease like the influenza pandemics of 1956 and 1968, and with the larger numbers corrresponding to the influenza pandemic of 1918.

Either way, a pandemic of these proportions would have a greatly crippling effect on society in several ways -- the proportion of the population ill and off work, the number of people demanding health care, and the number of deaths. US society is unaccustomed to coping with disruptions of this magnitude, and the consequences for our economy and security are worryingly difficult to estimate.