The World Health Organization says it's too early to know whether an entirely new disease is responsible for the deaths of more than 60 children in Cambodia.

The mystery disease has killed 61 of the 62 children who have been hospitalized since April. The affected patients, all of them under the age of seven so far, suffer a high fever, followed by a brain infection called encephalitis and severe breathing problems. It’s the respiratory problems that eventually kill the patients, often within 24 hours, doctors report.

Patients have turned up in several provinces in southern and central Cambodia.

But while many fear a new SARS or bird flu could be at hand, there's no indication the illness is spreading from person to person. Indeed, none of the hospital workers who are treating these sick children are becoming ill.

Dr. Nima Asgari of the WHO in Phnom Penh said Thursday that health workers are combing through victims' records to try to determine whether the problem is a combination of known ailments or a new disease.

Infectious diseases expert Dr. Neil Rau, who is not involved in the investigation, says there are too many unanswered questions right now to speculate on a cause. He says the WHO workers need to have a better understanding of the disease’s course.

“The part that I would be most interested in trying to figure out is whether this is kids who have a brain infection, known as encephalitis, or whether it’s kids with a respiratory illness, some of whom end up with encephalitis,” Rau told CTV’s Canada AM.

“If it’s a bad respiratory illness, there’s a possibility this could be something that’s transmitted person to person quite easily, whereas if it’s a brain infection, it’s less likely to be transferred person to person and therefore less likely to be a global concern.”

Rau says it’s interesting that no seniors have arrived in hospital with this illness as well, since most infectious diseases affect the extremes of age -- the very young and the very old – since they typically have weak immune systems.

“I have a feeling that once they start looking into further they will actually start to find more people who are elderly who have the same illness,” he said.

Rau says he’s reassured by comments from the WHO that they’re not seeing clusters of illness, which also suggests it’s not passing person to person.

“I have a feeling it’s more an environmental issue. In other words, kids who are being exposed to sick animals or to mosquitoes that are carrying a new cause of disease,” Rau said.

Dr. Beat Richner, the Swiss physician who first sounded the alarm about the outbreak, told the Phnom Penh Post that it’s possible that “wrong treatment” could be the culprit in the new illness.

“All these children had encephalitis and were hospitalized and treated at private clinics before coming to us,” Richner noted.

“I worry that a wrong treatment and drug intoxication at some private clinics has destroyed the lungs leading to a pneumonia we cannot treat.”

Nima Asgari, a WHO public health specialist also interviewed by The Phnom Penh Post, says there’s lots more investigation to be done.

“It is very early to find the cause. We are still trying to gather data,” Asgari said.