If a patient entered the Yale-New Haven Hospital emergency room with symptoms of acute diarrheal illness, odds were that doctors would not be able to tell the patient what caused them.

The Emerging Infectious Program of the Yale University Medical School, which recently received a $1.2 million grant, just finished a two-year study looking strictly at viral gastroenteritis, trying to solve the mystery surrounding this illness.

“There are approximately between two and four million episodes of diarrheal illness that occur in the United States each year, and of these, of the food-borne illnesses, we can only explain about 50 percent of the cases,” project coordinator Terry Rabatsky-Ehr said.

Awarded by the Association of American Medical Colleges and the Centers for Disease Control and Prevention, the three-year grant will help the Emerging Infectious Program establish a surveillance system for the causes of acute diarrheal illness in New Haven.

Dr. Robert Heimer, an associate professor of Epidemiology and Public Health and Pharmacology, will lead the study with other professors in various departments within the medical school.

“The grant really focuses on the burden of infectious diarrheal illness and that much of what we know about the illness is unexplained,” Rabatsky-Ehr said.

The newly funded Acute Diarrheal Disease Surveillance Study will look at patients with the illness and allow researchers to collect specimens from those patients and do both rudimentary and atypical laboratory tests. About two dozen causes of the illness are currently known, but they can account for no more than half the reported food-borne cases, leading the research team also to develop a bank of stored specimens for testing newly discovered pathogens in the future.

“We want to explain what’s causing this illness so that we can take effective control measures,” Rabatsky-Ehr said.

Once a suitable database of samples is established and proper testing methodologies are developed, these methodologies, if effective, could make their way to the state Department of Public Health for further development and use elsewhere.

But these types of studies are not new to Yale. Food-borne illness research, which is one branch of the Emerging Infectious Program, has been conducted since 1995, when the Emerging Infectious Program received its first grant from the CDC to work in connection with the Public Health Department. The program was instituted to conduct population-based epidemiological research on emerging and recurring infectious diseases.

“It really embodies a lot of what we’ve done already,” Rabatsky-Ehr said.

New Haven is also a prime place for such a study due to its rich diversity and Yale-New Haven Hospital.

“New Haven mirrors what we see throughout the United States, so it’s a good place to do this study,” Rabatsky-Ehr said.

The next big step in the project will be setting up the groundwork for the surveillance system in the primary care center of Yale-New Haven Hospital. Then potential patients can be identified and comprehensive testing may begin.