The man, who remains unidentified but is believed to be "patient zero" in Michigan, traveled to the Great Lake state from New York in March.
There is a chance for violent storms from Texas to Mississippi on Saturday.
New York City Mayor Bill de Blasio on Tuesday a declared a public health emergency in a heavily Orthodox Jewish section of Brooklyn amid a growing measles outbreak.
Britain's horse racing industry was on tenterhooks on Friday following an outbreak of equine flu with next month's showpiece Cheltenham Festival the focus of attention.
A shutdown in British horse racing due to an outbreak of equine influenza is costing the bookmaking industry tens of millions of pounds, Betfair said on Friday, and could get much worse if the outbreak is prolonged.