US is vulnerable to foodborne bioterrorism, CDC report says

Mar 19, 2002 (CIDRAP News) – The United States isincreasingly vulnerable to bioterrorist attacks on its food supply and needs tostrengthen its public health system to minimize the danger, according to areport published recently in The Lancetby officials from the Centers for Disease Control and Prevention (CDC).

Because the nation's food production system is becoming morecentralized, a bioterrorist attack using food as the vehicle could sicken manypeople over a large area, says the report by Jeremy Sobel, of the CDC'sFoodborne and Diarrheal Diseases Branch, and two CDC colleagues.

Their main theme is that the preparedness requirements forfoodborne bioterrorism are much the same as those for unintentional foodbornedisease outbreaks: robust surveillance, speedy investigation of outbreaks,laboratory-diagnostic capacity, and communication between care providers;local, state, and federal public-health agencies; and the news media.

Deliberate food contamination has occurred more than oncebefore in the United States, the report notes. In 1984, members of a religiouscult contaminated salad bars in The Dalles, Oregon, with Salmonellaenteritidis serotype typhimurium, causing 751 people to get sick. And in 1996, alaboratory worker used food contaminated with Shigella dysenteriae to infect colleagues.

Past accidental foodborne outbreaks have suggested thepotential for large numbers of casualties from foodborne bioterrorism, thereport says. For example, in 1994 an estimated 224,000 people were infectedduring an outbreak of S enteritidiscaused by contaminated liquid ice cream that was transported in tanker trucks.

The authors list the likeliest foodborne bioterror agents asbotulinum toxin, Salmonella, Shigella, Escherichia coli (including E coli O157:H7), and Vibrio cholerae. Iraq disclosed in 1995 that during the Persian GulfWar it had loaded 11,200 L of botulinum toxin into missile warheads, the reportsays. Missing from the list of likeliest agents is anthrax. Foodborne anthraxoccurs, albeit rarely, in developing countries where people eat raw orundercooked meat; it appears that the infectious dose is high and that thoroughcooking reduces the contamination level.

"Detection of outbreaks of foodborne illness depends onthe ability of clinicians and public-health officials to recognize clusters ofillness," the authors say. If patients were geographically dispersed, anoutbreak could escape notice until reports of notifiable diseases were analyzedat the state or national level. But the recent introduction of a Web-basednational foodborne disease outbreak reporting system has speeded reporting.

The article discusses several other surveillance programsand networks that supplement the reporting of notifiable diseases by cliniciansand laboratories to state health departments:

  • Intensive CDC and state surveillance for botulism cases
  • PulseNet, a network of public health and regulatory laboratories that do molecular subtyping of some foodborne pathogens
  • The Public Health Laboratory Information System, used to detect dispersed salmonellosis outbreaks
  • FoodNet, a joint program of the CDC, Food and Drug Administration, and US Department of Agriculture that involves active, population-based surveillance for enteric infections

Discussing the epidemiologic and medical responses tofoodborne bioterrorism, the authors say that a widespread outbreak could leadto shortages of medical supplies and personnel. For example, a botulismoutbreak could trigger shortages of ventilators, which are difficult totransport to scattered locations. To deal with that problem, local healthfacilities should be prepared to provide temporary manual ventilatory support.The article also discusses communication needs and capabilities for coping withfoodborne outbreaks.

The authors conclude that effective responses to foodbornebioterrorism will depend "on increasing awareness in the providercommunity, on building robust public health capacity to identify andinvestigate all outbreaks, and on preparedness to respond to events with manyillnesses."

Sobel J, Khan AS, Swerdlow DL. Threat of a biological terrorist attack on the US food supply: the CDCperspective. Lancet 2002;359(9309):874-80 [Abstract]

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