Disneyland has shut down two cooling towers after people who visited the California theme park came down with Legionnaires disease.
Health officials say an outbreak of the bacterial lung infection has sickened 12 people.
All of them spent time in Anaheim during the month of September.
Nine of the victims were guests or employees at Disneyland.
One patient, who had not visited the park, has died.
Legionnaires, which is caused by exposure to contaminated water or mist, can cause potentially fatal respiratory illness and pneumonia.
Older people and those with health problems are particularly at risk.
Park officials say the two cooling towers have been decontaminated and there is no longer any risk to those who visit or work at the park.