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New Foodborne Illness Numbers Dramatically Lower: Points To Danger Of Basing Public Policy On Faulty Statistics

For more than a decade, anyone addressing the issue of foodborne illness in the United States has had little choice but to use the so-called Mead estimates:

To better quantify the impact of foodborne diseases on health in the United States, we compiled and analyzed information from multiple surveillance systems and other sources. We estimate that foodborne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year.

Known pathogens account for an estimated 14 million illnesses, 60,000 hospitalizations, and 1,800 deaths. Three pathogens — Salmonella, Listeria, and Toxoplasma — are responsible for 1,500 deaths each year, more than 75% of those caused by known pathogens, while unknown agents account for the remaining 62 million illnesses, 265,000 hospitalizations, and 3,200 deaths.

Overall, foodborne diseases appear to cause more illnesses but fewer deaths than previously estimated.

Everyone in food safety has used these numbers, there has been nothing else, but we always viewed them with some skepticism. After all, the researchers found relatively small numbers of actual reported cases and then estimated multiples many times those reported cases that were unreported. In some cases, the conditions weren’t even reportable. So the Mead researchers found no reported cases of Norwalk-like viruses but estimated there were actually 23 million cases and, estimated again that 40% of these were due to foodborne illness.

The group led by Paul S. Mead was certainly composed of serious researchers — one of the researchers was Robert V. Tauxe, who contributed to the Pundit here — so there is no reason to think they didn’t do their best considering the data and methods available at the time. Still, there was a lot of estimating going on and the accuracy was questionable.

Also the big numbers — 76 million illnesses — lumped together what most people would consider serious problems, like people dying, with people simply getting a stomach ache. So the estimates have tended to warp public-policy decisions.

Now the Centers for Disease Control and Prevention have come out with new estimates:

CDC estimates that each year roughly 1 out of 6 Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die from foodborne diseases. The 2011 estimates provide the most accurate picture yet of which foodborne bacteria, viruses, microbes (“pathogens”) are causing the most illnesses in the United States, as well as estimating the number of foodborne illnesses without a known cause.

They also provided the estimate in great detail.

There is no question that it is a more accurate estimate. Still, the vast majority of the claimed illnesses are not actually known or identified; they remain extrapolations. In fact, more than 80% of the illnesses claimed not only are not known or verified — they are from “unspecified agents.”

Doubtless there is much to learn in studying this report, but three things scream out:

1) If over 80% of all foodborne illness is caused by unspecified agents, how useful can our policies be in preventing such illnesses?

2) Of those foodborne illnesses caused by one of 31 known pathogens, the majority (58%) are caused by Norovirus — what back in the old report were called Norwalk-like viruses. Yet this can be transmitted easily via cooks, waiters, plates, glasses, mom, etc. We cannot find in the study any sensitivity to distinguishing between a problem caused by production agriculture or food producers as opposed to a problem caused by waiters not washing hands properly. Lumping these together makes food safety policy difficult and should be addressed on the next go-around.

3) CDC emphasized over and over again the fact that these numbers are not directly comparable to the 1999 figures. For one thing, the new numbers exclude illnesses in the US that are sourced to travel to a foreign country. So if you go to Haiti and get a foodborne illness, when you return home to Miami and go to the doctor it doesn’t get counted under the new numbers.

This makes sense because the purpose of these numbers is to assist and assess our food safety policies. Nothing we do to the food supply here will help you if you are buying your food from a street vendor in Timbuktu.

Still, the dramatic drop from the 1999 numbers — and remember population has grown by over 30 million people since that study was done so all things being equal, you would expect the number to increase — leaves only two possibilities:

First, that our food safety system works and that food has actually been growing much safer. In this case, with our new food safety law, we just threw out a highly effective system.

Second, that the numbers were wildly inaccurate in 1999, in which case, public policy has been distorted by inaccurate information. There is little reason to think that a decade from now, there won’t be a new study pointing out that the one just announced is also wildly inaccurate.

Here are three articles to help understand the new study:

How Safe Is Our Food?
By J. Glenn Morris, Jr
University of Florida, Gainesville, FL

Foodborne Illness Acquired in the United States — Major Pathogens
By Elaine Scallan,1 Robert M. Hoekstra, Frederick J. Angulo, Robert V. Tauxe, Marc-Alain Widdowson, Sharon L. Roy, Jeffery L. Jones, and Patricia M. Griffin
Author affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia, USA 1Current affiliation: Colorado School of Public Health, Aurora, Colorado, USA.

Foodborne Illness Acquired in the United States — Unspecified Agents
By Elaine Scallan,1 Patricia M. Griffin, Frederick J. Angulo, Robert V. Tauxe, and Robert M. Hoekstra
Author affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Current affiliation: Colorado School of Public Health, Aurora, Colorado, USA.

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