I look for water systems being tampered with, to achieve scarerism in a very cheap stab at terrorism. One or two real poisoning would produce the desired result. If executed only in towns with mosques, Islam will get the blame and the terrorists will get the blame. Success for terrorism.
Y2K should have taught us all to have stored water in the house, 10 gallons person. The Red Cross's guideline is at a MINIMUM have 10 gallons for two weeks. I'd bet that less than 5% have such survival stores.