The Food Detectives

When an outbreak caused by contaminated spinach spread across the U.S. last summer, Ali Khan’s new CDC center was on the case / Mary J. Loftus

In the fifteen years that Ali Khan 00MPH has worked for the Centers for Disease Control and Prevention (CDC)—the federal agency responsible for safeguarding the public’s health—he has been to Singapore to track the SARS outbreak, led an anthrax response team to Washington, D.C., and traced monkeypox to prairie dogs in Indiana.

He was one of the main architects of the CDC’s public health bioterrorism preparedness program, and he flew to New Orleans on the agency’s jet just days after the levees broke and flooded the city.

Khan is now acting deputy director of the newest center at the CDC, the National Center for Zoonotic, Vector-borne, and Enteric Diseases, which was created last year to address health threats that exist at the juncture of humans, animals, and the environment.

These threats include diseases such as rabies, malaria, avian flu, and West Nile virus, agricultural terrorism, and water and foodborne illnesses such as those transmitted by undercooked hamburgers, suspect sprouts . . . or tainted spinach.

“I used to talk about Sherlock Holmes and Watson when I described my job, but now I say it’s like CSI,” says Khan, a native of Brooklyn who still has a hint of a New York accent. “You have a dead body, you have to find the clues, and new tools and technologies bring the package together. It’s not one person, it’s a team of people working collaboratively.”

Last summer, Khan and his center were faced with an outbreak that affected nearly every American who eats leafy greens: the fresh spinach Escherichia coli 0157 (E. coli) infections of August and September 2006.

Before it was over, there would be at least three confirmed deaths and hundreds sick or hospitalized with symptoms ranging from stabbing abdominal pains and bloody diarrhea to kidney failure.

A two-year-old boy died after drinking a spinach-fruit smoothie. The front page of the New York Times described parents standing vigil beside their nine-year-old’s hospital
bed, “watching his skinny, lanky body” endure dialysis and
blood transfusions. An active, seventy-seven-year-old former bank clerk from Wisconsin, whose son said she was fond of lettuce, spinach, and fresh fruit, died of kidney failure. All tested positive for the implicated strain of E. coli.

But many thousands more were protected by the quick action of CDC scientists, state public health officials, and food distributors and retailers.

“Producers and processors are as committed to good health as we are,” says Khan, discussing the case while taking a rare break in his office at the CDC’s main campus on Clifton Road. “No one out there wants to sell contaminated food.”

More than two hundred and fifty different foodborne diseases have been described in scientific literature, most caused by bacteria, viruses, and parasites. Some involve poisoning by harmful toxins or chemical contaminants. The CDC estimates that 76 million people get sick each year from food-related illnesses, more than 300,000 are hospitalized, and 5,000 die.

Although these statistics can be alarming, they shouldn’t deter anyone from eating produce and other nourishing foods, says Khan.

“We have one of the healthiest food supplies in the world,” he says. “The difference is that outbreaks used to be local and self-contained, such as potato salad at a church supper that made lots of people in the same town sick. That’s changed. Food can now be shipped thousands of miles from where it’s grown, and an outbreak can occur diffused across the country. We needed updated tools and tracking methods to keep up with these changes in the food landscape.”

Such high-tech tools and computer-based networks have been evolving at the CDC, as well as state health departments, for the past decade.

After a 1993 outbreak of E. coli in undercooked hamburgers from a fast-food chain in the western United States, PulseNet was developed—a national database coordinated by the CDC that allows public health officials to compare quickly the genetic “fingerprint” of disease-causing bacteria isolated from victims.

Groups of illnesses in different areas caused by the same strain should, in theory, become quickly apparent. On September 8, 2006, quick recognition of one such food outbreak is exactly what happened.

Wisconsin’s health department called the CDC about a small cluster of E. coli 0157 cases with matching subtypes. That same day, Oregon identified two E. coli 0157 cases that matched the strain. By September 13, the cases in Wisconsin had increased to seventeen, with six in Oregon.

The next day, thirteen states reported forty-five cases. State health departments, by comparing victims’ recollections and the contents of their refrigerators, already had established the common link: bagged spinach. The Food and Drug Administration (FDA) advised consumers not to eat bagged fresh spinach.

“Eighty percent of the cases occurred before September 8,” says Khan. “Quick detection allows us to shut down any new cases, to take preventive measures. In this case, there was a voluntary recall of all fresh spinach.”

The detective work involved at the front lines of public health, as well as the focus on education and prevention, are what drew Khan—a doctor who completed his residency in internal medicine and pediatrics—to the CDC. After joining the Epidemic Intelligence Service (EIS) in 1991, he is now a captain in the U.S. Public Health Service.

“It’s very rewarding to work at a population level, where you could be helping hundreds of thousands of people at a time,” he says. “I still practice clinical medicine one-on-one, because I enjoy my patients and like the satisfaction of making a diagnosis. In some ways, public health is an expansion of that.”

As an adjunct professor of epidemiology at Emory’s Rollins School of Public Health, Khan tells his students that, in Atlanta, they sit at the epicenter of public health in the nation.

“Geography can be destiny,” he says. “The CDC and Emory cross-pollinate. It took me five years to get my master’s of public health degree while working here, but I came out with a set of skills I didn’t have from my medical education.”

These skills include those used to trace a foodborne illness back from outbreak to victims to food source to suppliers. Tracking contaminated foods takes a massive, highly coordinated effort, from the teams that hit the ground running with household surveys in hand (“What fresh fruits and vegetables have you consumed in the last three weeks?”) to labs standing by to ID the strain.

The spinach that killed three and sickened more than two hundred was determined to have come from a Salinas Valley, California, spinach field. Public health officials believe it was likely contaminated by wild pigs in the area that tested positive for the same strain of E. coli.

Even though this outbreak is over and spinach is back on the market, other foodborne illnesses continue to make the news. In the last four months of 2006, federal health officials dealt with five multistate outbreaks of produce-related illnesses, including an October outbreak of salmonella associated with tomatoes in eighteen states and a December outbreak of E. coli caused by lettuce at several Taco Bell restaurants in the Northeast.

“I can’t say enough about the hard-working professionals in our foodborne diseases group,” says Khan. “Two of the outbreaks occurred simultaneously and the third followed on the heels of the other two; it was great work by a strong team.”

Overall, the CDC reports that rates of most forms of foodborne illnesses have dropped in the U.S. since the mid-1990s, including incidents involving the dangerous 0157 strain of E. coli, which fell by 29 percent. Khan (top, at an Ebola isolation ward in Uganda) hopes this engenders a certain level of confidence in the food chain.

“Please do not be afraid of your food,” says Khan, who admits to loving spinach—although he likes it cooked with some chili garlic sauce. “People should be more afraid of obesity and overeating. We need to encourage people to eat more fruits and vegetables, not to avoid them.”





 © 2007 Emory University