The number of Americans eating risky foods like undercooked ground beef, raw fish, oysters and runny eggs dropped by a third over a four-year period, according to survey results released on Tuesday.

The survey, made public at the International Conference on Emerging Infectious Diseases in Atlanta, led researchers to conclude that media reporting and public health education efforts on risky eating habits and food-borne illnesses may be working.

But people under 18 years old with compromised immune systems were much more likely - by 21 to 14 percent - to eat high-risk foods than healthy people of the same age, the survey found, leading researchers to believe they may have to target specific groups for education.

The proportion of people eating risky foods dropped from 31 percent in 1998 to 21 percent four years later, according to the results of telephone surveys of 15,000 to 20,000 people conducted by the Foodborne Diseases Active Surveillance Network, known as FoodNet.

The study looked at the consumption of seven foods known to be associated with infections by Escherichia coli, Vibrio, Salmonella and other food-borne pathogens - pink hamburger patties, pink ground beef, raw fresh fish, raw oysters, unpasteurized milk, runny eggs and alfalfa sprouts.

The survey found African Americans were the safest eaters, with only 15 percent consuming risky foods in the week before the surveys. Men ages 18 to 64 were more likely to eat risky foods than women of the same ages, by 38 percent to 30 percent.

Asians and Pacific islanders were more likely to consume risky foods than whites, by 32 percent to 21 percent.

The research was conducted by the U.S. Centers for Disease Control and Prevention along with the California Department of Health Services and other state health services.

The most common risky food people ate was runny eggs, the study found.