BEIJING, Nov. 12 (Xinhuanet) -- A wildlife biologist who was found dead at Grand Canyon National Park probably died of pneumonic plague, according to media reports Monday.

    Eric York, 37, was believed to contract the disease from a mountain lion carcass he worked with in a remote area of the park, which had probably died of the plague a week earlier.

    It is the first case of human plague infection recorded at the Grand Canyon, park officials said.

    Pamela Walls, parks spokeswoman, emphasized that York had limited contact with visitors and that, in any event, person-to-person transmission of the potentially fatal disease was highly unlikely.

    As a precaution, 49 of York's coworkers and others who had come near him were placed on antibiotics. Officials said no symptoms manifested in any of these individuals on medication.

    Pneumonic plague is one of the most deadly yet least common forms of the bacterial disease. It is most commonly transmitted to humans by flea bites and direct contact with infected animals. The last U.S. case of human-to-human transmission was in 1924.

    Medical literature states the early symptoms of pneumonic flu are virtually indistinguishable from less serious respiratory infections.

    Plague is caused by the bacterium Yersinia pestis; the disease killed millions across Europe in the Middle Ages.

    Today, just 10 to 15 cases are reported annually in the United States, primarily contained in the southwest.

    (Agencies)