The introduction of foot-and-mouth disease on American soil would have a tremendous effect on the U.S. economy, whether the outbreak is intentional or accidental, said Maureen McCarthy, the Homeland Security Department's senior adviser for weapons of mass destruction.

Speaking at the Association for Intelligence Officers' annual convention, she pointed out that such an outbreak would cost the American agriculture economy "hundreds of billions" of dollars and could shutter some trade borders for "years." 

It will happen immediately even if there are no deaths, she said of the financial and trade impact.

McCarthy said foot-and-mouth disease could be used by terrorists. While there's no proof that such a plot is brewing, domestic agriculture could be a salient target because of the nation's dependence on the sector. She added that simultaneous breakouts of foot-and-mouth disease in several locations could signal an attack.

Acknowledging the potential for disastrous consequences for agriculture and the American economy, Kimothy Smith, DHS chief veterinarian and acting director of national biosurveillance, said that in the event of a foot-and-mouth outbreak, it would be possible to implement import bans on a nation-by-nation basis.

The disease is worrisome to health officials because it is highly contagious, sometimes lethal to humans and can spread even in freezing temperatures. There has not been an outbreak in the United States since 1929. However, infection rates in some other countries have grown to endemic proportions, McCarthy said. Pakistan and Afghanistan have had the highest infection rates. Other regions, including South America and Southeast Asia, also have reported outbreaks, and China reported a case in cattle last month.