As long as the terrorists have people believing that everything that happens in the counrty is a result of terrorism, then they are winning.
Norwalk and Norwalk like virus's have been around for thrity something years, with over 180,000 people in the country getting it each and every year. The 180,000 is the confirmed number of cases, the CDC estimates that 23 million people get it a year in this country.
We hear about it from Cruise ships because the cruise ships are required by law to report gastrointestinal complaits to the CDC, and recently tests were developed to be able to confirm it was the Norwalk Virus. Ever have a 24 hour "Stomach Flu"? Probably the Norwalk Virus.
You don't hear about it on the national news from the restaurant in Utah, the hospital on Long Island, the schools in North Carolinia, the Hospital in Toronto, the rafting Camp in Colorado, the two facilities in Michigan that officials won't yet name, the 1,000 people in Minnisota in 25 outbreaks that have suffered from it since November 1, the nursing home in New Hampshire with 4 dozen people sick, and on and on and on.
So unless the terrorists have been working for 30 something years on this, it's not terrorism, it's the news going nuts with something that isn't news.