A wildlife biologist at Grand Canyon National Park likely died from the plague through his exposure to wild animals that can carry the disease, the National Park Service said Friday.

Eric York, 37, was found dead in his home Nov. 2. Following his death, about 30 people who came in contact with him were given antibiotics as a precaution.

While authorities were uncertain about how York became infected, officials said that the biologist was at a greater risk to the sometimes-fatal disease through his exposure to wild rodents and mountain lions.

Park Service officials initially said they suspected the plague or hantavirus, another sometimes-fatal disease endemic to the Southwest, because of York's interests and hobbies.

Health officials in Arizona warned in September that the plague appeared to be on the rise and that more cases were likely after an Apache County woman was infected with the disease.

While Arizona health officials say the disease appears to be on the rise in the state, CDC spokeswoman Lola Russell said plague cases weren't on the rise nationally.

Plague is transmitted primarily by fleas and direct contact with infected animals. When the disease causes pneumonia, it can be transmitted from an infected person to a non-infected person by airborne cough droplets.

Cases are treatable with antibiotics, but the Centers for Disease Control and Prevention reports that up to 50 percent are fatal if the disease causes pneumonia. The Coconino County Medical Examiner has said York's lungs were filled with fluid and his body showed signs of pneumonia.