Avian Flu Diary: Recalculating The H1N1 Death Toll

# 3988

This is something we’ve discussed many times before, most recently last Saturday with When No Number Is Right.

It is impossible to accurately `count’ flu deaths in this country. We don’t count them during a normal flu season, and we certainly can’t count them during a pandemic.

The often parroted number of `36,000' flu deaths annually’ in the United States isn’t the result of a count – it is the result of an averaging of estimated annual excess deaths during flu season over nearly a decade.

That range of estimated excess deaths ran from 17,000 to 52,000.

Here is how the CDC describes the process.

How did CDC estimate that an average of 36,000 people die in the U.S. each year from seasonal flu?

This statistic came from a 2003 JAMA study by CDC scientists [10]. The study used statistical modeling to estimate that during 9 influenza seasons from 1990-91 through 1998-99, an annual average of 36,000 flu-related deaths occurred among people whose underlying cause of death on their death certificate was listed as a respiratory or circulatory disease. A 2009 study that appeared in the journal Influenza and Other Respiratory Viruses made a similar estimate for the 10 influenza seasons from 1993 to 2003 [9].

These numbers are not without their critics, and in 2005 Peter Doshi published a challenge to these models in the BMJ (doi:10.1136/ bmj.331.7529.1412) where he argued that the 36,000 deaths a year is badly overstated.

On Saturday, I alluded to the fact that the CDC was working on new estimates of infections, hospitalizations, and deaths . . . and we ought to be hearing about those in the next few weeks.

These won’t be `count's’ of course, they will be estimates, and they will involve likely ranges. But they should give us a better idea of the impact of the H1N1 virus.

Donald G. McNeil Jr, of the New York Times picks up the story with word that those estimates are under review, and should be released in the next week or two.

Recalculating the Tally in Swine Flu Deaths

By DONALD G. McNEIL Jr.

Published: November 10, 2009

About 4,000 Americans — rather than about 1,200 — have died of swine flu since the disease emerged in April, according to new figures being calculated by epidemiologists for the Centers for Disease Control and Prevention.

The larger number of deaths does not mean the virus is more dangerous. Rather, it is a new estimate made by combining deaths from laboratory-confirmed cases of the flu and deaths that appear to be brought on by flu, even though the patient may have ultimately died of bacterial pneumonia, other infections or organ failure.

The new estimate of deaths — actually a range both larger and smaller than 4,000 — will not be released until sometime next week because the centers’ consultants are still looking over the figures, said Glen Nowak, a C.D.C. spokesman.

The new estimate will be a more accurate comparison to the 36,000 deaths from seasonal flu each year, he said. That estimate is also based on confirmed cases as well as hospital reports of people who appear to have died after a bout of flu. Over 90 percent of seasonal flu victims are over 65, and many are bedridden or in nursing homes or have serious medical problems like cancer or heart disease that the flu worsens.

The new estimate “does sound much more reasonable,” said Ira M. Longini Jr., a flu epidemiologist at the University of Washington. “It doesn’t surprise me that it’s higher.”

(Continue . . . )

For more perspective on the difficulties involved in determining the actual number of H1N1 deaths – or even the death toll from seasonal flu - you may wish to check these blogs from the past 6 months.