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When it comes to food poisoning, people usually blame the last thing they ate for making them sick. That's a common mistake, says Barbara Mahon, an epidemiologist with the Centers for Disease Control and Prevention (CDC) and a former faculty member in the Boston University School of Public Health (BUSPH) Department of Epidemiology.
"It is impossible to know what food made any individual person sick," said Mahon, MD, MPH, who spoke about foodborne illnesses at the Feb. 10 BUSPH Public Health Forum, "What Not to Eat: Foodborne Illness Update 2010." The incubation time of a pathogen or toxin can take anywhere from one day to a month, she said, making it a challenge to figure out what made someone sick.
Recently, foodborne illnesses, like cookie dough contaminated with E. coli or infections from Salmonella linked to peanut products, have been making national headlines and unsettling the public. Last spring, President Obama announced an overhaul of the current food safety system and created a Food Safety Working Group to modernize food contamination laws.
"I think we've certainly come a long way," said Mahon, but added, "we still have a major problem with foodborne illness."
There are approximately 76 million cases of foodborne illnesses reported each year, said Mahon. Annually, there are 325,000 hospitalizations and 5,000 deaths related to foodborne diseases, according to CDC estimates.
For the last year, Mahon, a pediatrician and an adjunct assistant professor of epidemiology at BUSPH, has been head of the FoodNet and Outbreak Surveillance Team in the Enteric Diseases Epidemiology Branch at the CDC. Mahon's team is not only in charge of the FoodNet active foodborne disease surveillance system, but also tracks outbreaks of food-borne disease across the country.
"The challenges keep coming," Mahon said. "We keep learning."
A broad range of foods -- from oysters to bagged spinach to tomatoes to alfalfa sprouts -- can be contaminated, normally with animal feces, causing illness, she said.
Foodborne illnesses have been affected by several trends, Mahon explained. Decades ago, food was largely locally produced and consumed, making foodborne illnesses easier to detect. But today, in the United States, food is centrally produced. Four companies control 50 percent of the chickens and 80 percent of the beef in the country. Food is also distributed widely, making it hard to trace the outbreak's origin and figure out what went wrong. Also, more than 250 pathogens and toxins are transmitted by food.
"When things go wrong, there's the potential for very big outbreaks," Mahon told the audience of faculty and students.
PulseNet, a new foodborne disease surveillance network, is an "absolute breakthrough" in enabling quick pinpointing of disease outbreaks, said Mahon. PulseNet epidemiologists perform DNA "fingerprinting" on disease-causing bacteria isolated from humans and from suspected food. These "fingerprints" are collected in a database at the CDC. It allows real-time communication between epidemiologists and can help them quickly identify the source of an outbreak.
In order to prevent more people from getting sick in the future, Mahon suggested improving public health surveillance of foodborne diseases, more thoroughly investigating new outbreaks of illness and translating the lessons learned into public policy. The current economic recession, however, has resulted in cut backs to public health staffing and fewer public epidemiologists, she said. There are fewer public health officials to take advantage of resources like PulseNet.
"The capacity to investigate outbreaks is in a decline," Mahon said. "It's a shame because these are missed opportunities for prevention."
From 2002 to 2007, Mahon was a full-time faculty member in the Department of Epidemiology, which sponsored the forum.