Experts Seek Root of Illness Among Berries
In the highly specialized world of microbiology, Dr. David Relman occupies an unusual niche: He drafts genetic blueprints of “novel organisms”--disease-causing bugs that scientists have been unable to classify because they cannot be grown in the laboratory.
It is a relatively obscure pursuit. So no one was more surprised than the Stanford University researcher at the big news generated by the object of his latest scientific paper: a little-known parasite called cyclospora, which rarely turns up in the United States.
“If we were sitting in Bangkok, I’d tell you, ‘This is an important problem, a threat to all of us,’ ” Relman said. “But as of last year, if you had asked me if this is a problem in the United States, I’d say, ‘Not now, but it could be.’ ”
Today, the American public is getting a quick education in the workings of cyclospora, an exotic microbe that in recent weeks has emerged as the suspected cause of gastrointestinal illness in nearly 1,000 people in 11 states. Federal and state health officials across the country are now racing to find the source of the parasite, which causes severe diarrhea and, authorities suspect, is being spread through contaminated berries.
Although the disease has surfaced only east of the Rocky Mountains, California figures prominently in the investigation. California produces 80% of the nation’s strawberries, the fruit that has generated the most speculation as the source of the parasite. Florida produces roughly 10%, and the rest come from other states.
California health officials said they have turned up no traces of cyclospora after two weeks of testing strawberries, water and soil, and federal officials have been shifting their attention to raspberries and other fruits.
“We’re not really prepared to say it’s this berry versus that berry,” said Dr. Sue Binder, a top official at the federal Centers for Disease Control and Prevention. “We don’t feel we can say confidently which fruit, or even which country or which farm.”
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But strawberry farmers are in an uproar over news accounts on the East Coast that, coming at the height of the summer fruit season, have hurt sales in cities from Boston to Houston to Detroit.
“We’re a victim of coincidence,” said Theresa Thorne, spokeswoman for the California Strawberry Commission, which represents the state’s 600 growers. She said the commission will be convening a panel of scientists to investigate cyclospora. “When consumer confidence is shaken, it is very difficult to restore. We’re going to clear our name through science.”
The investigation is proceeding at a rapid clip. Working nights and weekends, dozens of federal and state epidemiologists are interviewing patients afflicted with cyclospora. U.S. Food and Drug Administration investigators are conducting “trace-back investigations,” in which they examine records to trace suspected foods to their source.
Scientists at both the FDA and the CDC, as well as in various states, are analyzing fruit and samples of water and soil. They are hunting an elusive organism--a one-cell microbe that looks like a glass marble when viewed under a microscope and takes on a fluorescent blue cast when examined under ultraviolet light.
“We’re getting closer to figuring out what the potential causes of these outbreaks are, but we still have lots of questions and we are still early in the investigation,” Binder said.
Tracking the cyclospora bug is tricky. First, the parasite does not produce symptoms until a week after infection. For medical detectives, that lag time often means the trail has gone cold: Patients don’t remember what they ate a week ago and leftovers are rarely available for testing.
Second, testing for cyclospora is difficult. While common in developing countries, the organism has only been identified recently and had caused only three small outbreaks in the United States before the current problem. Thus sophisticated testing techniques such as one recently developed by Relman are not widely available.
The first known cases of cyclospora were diagnosed in 1977 and first reported in 1979. The illness is easily treated with antibiotics, but lack of treatment can lead to severe diarrhea as well as loss of appetite, weight loss, nausea, vomiting, fatigue and fever.
Little is known about cyclospora’s life cycle, or whether it can infect animals as well as humans. Scientists say transmission from person to person is highly unlikely. The illness usually spreads through infected feces that can contaminate either water or food.
The epidemic is the latest in a string of so-called “emerging infections,” diseases such as AIDS, Legionnaire’s and Lyme that are caused by previously unrecognized viruses and microorganisms.
