A combination of pathogens is being blamed for the mystery illness that has claimed the lives of scores of children in Cambodia, CNN said Wednesday. Medical doctors familiar with a World Health Organization investigation into the illness told CNN the agency, working with the Cambodian health ministry, had reached that conclusion -- which is yet to be made public. The illness has resulted in the deaths of more than 60 children in Cambodia. The suspect pathogens include enterovirus 71, streptococcus suis and dengue, the sources told CNN. They said inappropriate use of steroids, which can suppress the immune system, worsened the illness in a majority of the patients, the report said. The WHO was expected to advise health care workers to refrain from using steroids in patients with signs and symptoms of the infection, which include severe fever, encephalitis, and breathing difficulties, the report said. Earlier reports had said most of the children stricken by the illness were younger than age 3.