Restaurants are still falling short on several key foodborne illness prevention practices, according to a series of recent reports by the Centers for Disease Control and Prevention.

Restaurant food preparation and handling practices, worker health policies, and basics such as hand washing are factors that are often not reported during an outbreak, despite the fact that about half of the 48 million cases of foodborne illness that occur in the U.S. each year are associated with restaurants or delis, the CDC said. About 3,000 of the annual cases of foodborne illness are fatal.

The problem is in part because too little is known about the overall environmental factors that can lead to a foodborne illness outbreak and how they are investigated, the CDC said.

“Inspectors have not had a formal system to capture and report the underlying factors that likely contribute to foodborne outbreaks or a way to inform prevention strategies and implement routine corrective measures in restaurants, delis and schools to prevent future outbreaks,” said Carol Selman, head of the CDC’s Environmental Health Specialist Network team at the National Center for Environmental Health.

The report, however, pointed to systemic, rather than industry-wide, food safety problems, and are more likely to impact independent restaurants than chains, said Bill Marler, a personal injury attorney and foodborne illness expert who frequently files lawsuits on behalf of victims.

Big players, including multi-state restaurant operators and organizations like the National Restaurant Association have “done a remarkably good job” of improving food safety practices over the past decade, said Marler.

“The number of outbreaks at those sorts of restaurants have diminished substantially,” he said, while independents and smaller chains have become an area of greater concern. “The difference is resources and management,” he said.

According to the CDC report, the common practice of foodservice employees showing up for work when they’re sick continues to present a problem.

In a survey of 491 restaurant food workers, 20 percent said they had worked at least one shift in the past year despite being sick with vomiting or diarrhea, which are symptoms of foodborne illness. Workers expressed concern about leaving co-workers short-staffed and losing their job, the researchers found.

Policies that encourage workers to report illness to managers would mitigate such pressures, the report said.