In a study of restaurant food handling and foodborne illness, about 12 percent of the servers and preparers interviewed told public health researchers they had worked while sick with vomiting and diarrhea.

The busier the restaurant, the more reluctant the employees were to call in sick, the study found.

Titled “Factors Associated with Food Workers Working While Experiencing Vomiting or Diarrhea,” the study was a collaborative effort by universities, federal public health agencies and state and local health departments that participate in the Environmental Health Specialists Network. The EHS-Net states are California, Connecticut, New York, Georgia, Iowa, Minnesota, Oregon, Rhode Island and Tennessee.

The study findings were published in the Feb. 3, 2011 edition of the Journal of Food Protection.

About 20 percent of foodborne illness outbreaks involve pathogens that were transmitted to food by food handlers, the study notes. And while diarrhea and vomiting are common symptoms of some foodborne infections, the study doesn’t mention that infected people are sometimes asymptomatic (or that diarrhea and vomiting don’t always signal foodborne illness).

Efforts by the U.S. Food and Drug Administration to prevent contamination in the food service industry have included encouraging hand washing, gloves to prevent bare-hand contact with ready-to-eat food, and excluding ill workers from the workplace. 

So the study–one of the first of its kind, the authors say–sought to explain why people who prepare and serve food would come to work if they were ill.  

Restaurants were chosen at random within certain areas and interviews were conducted with a kitchen manager and one to two food workers, chosen by the manager. Of the 486 food workers interviewed, 52 percent were female, 55.5 percent had a high school degree, and 40 percent were between 21-30 years old.

According to the findings, 58 (11.9 percent) said that during two or more shifts in the previous year they had served food while they were sick, and their symptoms included vomiting and diarrhea. 

The factor most associated with whether a food handler worked while sick was the restaurants’ workload–restaurants that served more than 300 meals on their busiest days were the most likely to have had sick employees on duty.

Not surprisingly, the lack of a policy requiring workers to report their illness and the lack of on-call substitutes were also contributing factors. 

Lack of manager experience also played a role. The study authors speculate that experienced managers might know their employees better and be better able to determine the nature of their illnesses and whether they should work.  Whether a manager had food safety training or certification made no difference.

Male food handlers were more likely to come to work sick than female food handlers.

Workers who had paid sick leave were approximately twice less likely to say they had worked while vomiting and experiencing diarrhea, but the researchers say the number was not statistically significant.

The authors acknowledge the study’s many limitations: the food workers were not chosen randomly but selected by managers, information about their illnesses was self-reported, some of the interviews took place within the managers’ hearing range, and budget constraints prevented the use of translators, so everyone interviewed spoke English. 

One can’t generalize beyond the restaurants in the study, the authors caution.

But the researchers conclude the obvious–that the number of food handlers who work when they’re sick would be reduced if establishments encouraged employees to acknowledge their illness and if there were no pressures to work while ill.

And the authors suggest that restaurants, especially busy restaurants, should make it acceptable for ill food-handling staff to call in sick given the risk and costs of poisoning customers.

“Investments in such policies may be cost-effective interventions for restaurants, given restaurants’ substantial financial losses associated with foodborne illness outbreaks,” the authors write.  “Given our finding of an increased likelihood that workers in high-volume restaurants will work while ill, such investments could be particularly important for high-volume restaurants.”

Most local food-code regulations require ill food handlers to stay home.