A deadly virus carried by mice - that causes an incurable lung disease known as Hantavirus Pulmonary Syndrome - has been spreading from California's Yosemite National Park, a British media report said Sunday.
Two men have died from the disease, and four have survived, the Daily Express reported citing the US' Centre for Disease Control and Prevention.
Although four million people visit Yosemite every year, the area of contagion is believed to be confined to a popular camping spot known as "Curry Village".
US officials have so far contacted 3,000 out of 10,000 holidaymakers known to have booked tents there during the peak summer months.
People who stayed in tents between June 10 and Aug 24 may be at risk of developing the disease, they said.
Park officials closed 91 tents after discovering infestations of the deer mice.
The mice are able to burrow through pencil-sized holes, nesting between the double walls of the cabins.
Hantavirus is carried in their faeces, urine and saliva. When dried and, once mixed with dust, it is easily inhaled in small, confined and poorly ventilated spaces.
People can also be infected by eating contaminated food, touching surfaces or by being bitten by the mice.
Flu-like symptoms, such as fever, headaches, muscle pains, coughing and breathing difficulty, can appear six weeks or more after exposure.
The virus is, however, not known to be contagious between humans.