FRESNO (AP) — Yosemite National Park officials are saying up to 10,000 people who were guests in certain lodging cabins might have been exposed to a deadly mouse-borne virus.

Park concessionaire Delaware North Co. sent letters and emails this week to nearly 3,000 people who reserved the insulated “Signature” cabins between June and August, warning them that they might have been exposed.

The cabins hold up to four people. Spokesman Scott Gediman said Friday that could mean up to 7,000 more visitors might have been exposed.

The park is receiving more than 1,000 calls a day as visitors frightened about a growing outbreak flood phone lines seeking reassurance.

Six people have contracted the virus, two of whom have died.

(Copyright 2012 The Associated Press.)