Three factors primarily are responsible for the jump: increased imports of fresh produce, increased consumption, and better detection and reporting of food-borne illnesses, food safety experts said.
"There's clearly a trend of produce outbreaks," said Caroline Smith DeWaal, director of food safety for the Center for Science in the Public Interest, a nonprofit consumer advocacy group in Washington, D.C. "One of the things that is quite striking in the produce outbreaks is the (number of cases of) illnesses are quite large."
Between 1990 and 2002, produce caused 293, or 15.3 percent, of 1,925 food-borne outbreaks. The fruit and vegetable outbreaks sickened 28 percent of those infected -- more than 18,000 people, according to Center for Science in the Public Interest reports.
Mexican-grown green onions caused last fall's hepatitis A outbreak at Chi-Chi's at the Beaver Valley Mall, state and federal public health officials said. Sickened were 660 people, including three who died, in the nation's largest food-borne outbreak of hepatitis A tied to a single restaurant.
Each produce outbreak sickens, on average, about 60 people, said Smith DeWaal.
"I think it's critical to note that most produce doesn't make you sick, and there's huge benefits to eating fruits and vegetables," she said. "We want the problems cleaned up before they get to consumers," a task that is "incumbent on the government."
The U.S. Food and Drug Administration, which inspects produce and traces its origins in outbreak investigations, is developing a produce safety plan focusing on research, risk assessment and education, said Nega Beru, director of the FDA's division of plant product safety.
"It is a high priority for us this year, mainly to reduce the number of outbreaks from produce," he said.
Consumption of fresh fruits and vegetables rose 16.4 percent in the United States from 1990 to 2000, then dropped 3 percent from 2001 to 2002, according to the Produce Marketing Association, a global trade association.
Produce imports rose 45.7 percent between 1993 and 2000, according to the organization.
Sixty-nine percent of imported vegetables come from Mexico. Chile, at 19 percent, is the largest fruit supplier, followed by Mexico and Costa Rica, each with 18 percent, according to the Produce Marketing Association.
The North American Free Trade Agreement, implemented on Jan. 1, 1994, eased trade barriers among the United States, Canada and Mexico. But FDA officials can't regulate foreign businesses. The agency does stop imports from specific companies from getting into this country after a problem has been discovered.
"FDA needs significant new authority to actually look at food safety issues on the farms, both foreign and domestic," Smith DeWaal said.
The agency should be able to certify foreign farms and processors who export food to the United States, she said.
About 40 percent of produce outbreaks are caused by the same hazards found in meat outbreaks, such as E. coli or salmonella, she said.
The FDA generally does not announce the source of a produce outbreak until investigators trace it to the grower, she said.
"That may have been the case in the past, but that may be changing," the FDA's Beru said. "That whole issue is being revisited."
In September, more than 300 people were infected with hepatitis A in Tennessee, Georgia and North Carolina.
Federal authorities and officials in those states announced Oct. 9 that green onions were the likely cause of the Georgia and Tennessee outbreaks even before they had traced the onions to Mexican growers.
Most people sickened by hepatitis A in the Beaver County outbreak ate at Chi-Chi's between Oct. 6 and 9, but did not get sick for several weeks.
Smith DeWaal said the FDA's emphasis should be on protecting the public.
"The policy today is designed to protect the industry, but it clearly is costly to the public. In Pennsylvania, three people died. It's possible those might have been prevented if information was known earlier about the cause of the three earlier outbreaks," she said.
"We always look at what the best time is to notify the public," said an FDA spokesman. "I think the policy is whenever there is a danger, we're going to let the public know."
Since 1998, the FDA has been testing small numbers of imported and domestic produce for potential hazards, including salmonella, E. coli and shigella, to try to determine how prevalent contamination might be, Beru said.
This month, the agency sent letters to companies that handle or grow lettuce and tomatoes, warning them to follow proper growing and handling procedures or face enforcement actions.
The letter was prompted by 14 outbreaks linked to those vegetables since 1996, making 859 people ill.
The FDA is asking Congress for $7 million to increase inspections of foreign produce, part of the FDA's $1.8 billion budget request for fiscal 2005 and part of $65 million slated for defending the nation's food supply against bioterrorism.
This would enable the agency to do 97,000 inspections in 2005, a 60 percent increase from fiscal 2003.
In fiscal 2005, the FDA plans to inspect 26,000 domestic firms, nearly 11 times the inspections during fiscal 2001.
Even when a vegetable or fruit is linked to an outbreak, the product usually is not recalled, as in outbreaks caused by meat or poultry, Smith DeWaal said. Recalls should be considered, she said.
"In outbreaks involving vegetables and fruits, the food is rarely recalled because by the time they discover the source, FDA says the food is usually consumed. ... That clearly was not the case in Pennsylvania."