Most of the children who contracted the illness have come from the south of Cambodia, though officials did not find a "cluster" -- a lot of cases in one area.
The World Health Organization has determined that a combination of pathogens -- disease-causing micro-organisms -- caused the illness. The WHO reached the conclusion in conjunction with the Cambodian Ministry of Health, CNN said.
Inappropriate use of steroids, which can suppress the immune system, made the illness worse in a majority of the patients, the doctors told CNN.
The broadcaster said the pathogens include enterovirus 71, known to cause neurological disease, as well as streptococcus suis, known to cause infections like bacterial meningitis in those who have close contact with pigs or pork products. The pathogens also include dengue, transmitted by mosquitoes.
CNN said the WHO sources wanted to remain unidentified because the results of the health organization's investigation have not yet been made public.