LOS ANGELES, CA (Catholic Online) - Most of the cases so far have come from southern Cambodia, with no apparent links between the individual cases. The World Health Organization reassures the public that there are no signs yet of contagion.

"To date, there is no report of any staff or any neighboring patients to the cases at the hospitals becoming sick with similar symptoms," the agency said.

Dr. Nima Asgari, a public health specialist for the U.N. body in Cambodia says it was difficult to specify the symptoms, which "include high fever and severe chest disease symptoms, plus in some children there were signs of neurological involvement." Asgari says that the medical investigation is still at an early stage.

The doctor confirmed there was "no cluster of the cases yet" but said the high mortality rate in such a short space of time was worrisome.

"WHO is always concerned about a disease which causes death in such high numbers of children," he told journalists.

The victims to date have all been all seven years of age or younger. The majority of the victims were three years old or younger, Reuters reported. The children were admitted to hospitals in the capital Phnom Penh and the northwestern tourist hub of Siem Reap.

There's no indication that is it spreading from person to person, WHO spokeswoman Aphaluck Bhatiasevi said.

Health workers are trying to determine whether the cases were all the same disease or a collection of various illnesses. Neighboring countries have also been alerted.

The United Nations agency said in a June 30 report that the clinical signs of those afflicted with the disease "appear unusual." No other hospital patients or staff in Phnom Penh had fallen ill with similar symptoms, WHO said.

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