Carole Sugarman, a former Washington Post food reporter, now covers the Agriculture Department for Food Chemical News, reports that the CDC estimates that there are 76 million cases of food-borne illness a year in the United States, a problem that sends nearly 325,000 people a year to the hospital; 5,000 a year die from it. The young, the old and the immune-compromised are hit hardest.

Patricia Griffin, chief of the food-borne disease branch of the CDC, said that an emergency room physician recently told her that she doesn’t take stool cultures anymore since the results generally don’t come back for a couple of days — after the patient has been discharged. Plus, she said, a positive result wouldn’t affect treatment: Although the type and severity of food-borne disease determines the specific therapy, many infections are not treated with antibiotics or anti-diarrhea medications. That’s because antibiotics can complicate the condition and possibly lead to drug resistance, and anti-diarrheals keep the disease-causing bacteria in the system rather than help get it out. Since in many cases, there’s no treatment other than keeping hydrated, doctors may figure it’s fruitless to take a culture. "In their minds, they’re not going to do anything different," Griffin said.

Although state procedures vary somewhat, the basic protocol for responding to a suspected food-borne illness is this: If a stool sample tests positive for food-borne bacteria, the results are supposed to be reported to the state, which then alerts the CDC. The hospital or private lab is urged to send a sample of the bacteria to the state, which does further testing to determine the serotype — the specific strain of the bacteria identified. Knowing the serotype may help identify the food that caused the problem, since certain serotypes are more common to specific foods. Monitoring serotypes also helps the CDC keep tabs on which strains are increasing in prevalence and which are decreasing.

The state labs may also take a genetic fingerprint of the bacteria and enter it into a CDC database, to see if there are any matches. Since food processors distribute their food nationwide, people in Maine and California could get sick from the same firm’s hamburgers. DNA matches could help spot outbreaks and stop them from spreading.

The good news: E. coli O157:H7, campylobacter, cryptosporidium, listeria and yersinia — underwent significant declines in 2004, compared with 1996-1998. The bad news: Salmonella infections showed the smallest decline. Of 15,806 laboratory-diagnosed cases of food-borne infections from the 10 states under CDC surveillance, more cases — 6,464 — were from salmonella than any other bug, but the CDC estimates that 38 cases occur for every one that’s actually reported.

Figuring out what made an individual person get sick often is impossible. "Sometimes you can, sometimes you can’t," said Donna Rosenbaum, a food safety consultant and the first executive director of Safe Tables Our Priority (STOP), an advocacy group for victims of food-borne disease. "Occasionally you get lucky."