WASHINGTON -- It was the nation's largest salmonella outbreak. The culprit, contaminated ice cream, was recalled amid headlines about food poisoning. Many consumers dismissed the threat, ate the tainted ice cream -- and got sick.
The lesson? Health workers must do a much better job warning the public when they discover tainted foods, doctors reported Wednesday in the first study of how effective recalls of unsafe food truly are.
"What ... customers didn't know did hurt them," concluded Dr. Barbara Mahon, who investigated the salmonella outbreak for the Centers for Disease Control and Prevention.
Because of changes in the nation's food supply, "the risk of widespread outbreaks like this one seems to be increasing," she said. "It's probably never going to be possible to get 100 percent of the people to hear a (warning) message or to believe it. But I suspect we can do a lot better."
A consumer advocate said preventing further illness as soon as tainted foods are discovered is a constant struggle. "What we have here is a time bomb. If recalls aren't done quickly and well, people will get sick, and some people will die, unnecessarily," said Michael Jacobson of the Center for Science in the Public Interest.
Yet government regulators don't have the legal authority to mandate recalls of suspect foods. Even when manufacturers voluntarily recall tainted foods, they often do not adequately warn that continuing to eat the product is dangerous, Jacobson said.
Although a recall removes unsafe food from store shelves, public warnings are necessary to alert customers who already have the food in their homes.
Mahon investigated a 1994 salmonella outbreak blamed for sickening 224,000 Americans who ate bacteria-tainted Schwan's ice cream. The contamination was traced to a trucking firm that carried ice cream mix to the Schwan's Inc. factory in the same tanks it used to carry raw eggs, a common salmonella culprit.
This outbreak was unique: The Minnesota company delivers frozen foods directly to customers' houses, so, unlike in most food-poisoning cases, scientists could test whether consumers heard and heeded the recall.
In October 1994, two weeks after Schwan's recalled the suspect ice cream, workers from CDC and Georgia's health department surveyed 179 Georgia households that bought Schwan's products.
Despite warning letters mailed by Schwan's and widespread news coverage, 9 percent of customers still had not heard of the salmonella risk. Customers who had heard reported first learning of the warning a median of five days after the recall.
Worse, "a very high percentage didn't really think (the recall) applied to them," Mahon said. "Basically, they just didn't believe it."
Thirty-six percent of those surveyed did not understand that recalled ice cream should not be eaten. And in 31 percent of the households, someone ate the ice cream after hearing about the salmonella threat, she reported in Wednesday's American Journal of Public Health.
Mahon estimated that about 51,000 Georgians ate the ice cream, and 11,000 took ill. About 1,760 of those cases occurred after the recall, she said, "and therefore might have been prevented" by better warnings.
Because the media are the main vehicle for public health warnings to reach consumers, Mahon also examined news coverage of the outbreak. Of 64 news reports published or aired in Georgia, only 6 percent actually said not to eat the recalled ice cream. So Mahon, now with New Jersey's University of Medicine and Dentistry, advised health workers subject to media interviews about outbreaks to communicate clearly how consumers can protect themselves.
In addition, the government should ensure that manufacturers thoroughly communicate the risk when a food is recalled, she said.