I'm not buying it. There are too many outside variables. And as one commenter points out, this disease seems unusually concentrated in the USA. Also, any animal in constant proximity to humans is likely less lean than its wild counterparts.
And HIV is unusually concentrated in Africa. And cholera is endemic in south Asia (thus leading to suspicions that UN troops from Nepal are the source of the cholera outbreak in Haiti). It's not unheard of for infectious agents to be geographically localized.