The latest review of records from Cambodia's Ministry of Health turned up enterovirus 71 in a large number of cases looked at as part of the WHO investigation into the unidentified illness that has claimed the lives of 52 children since April.
Enterovirus 71 causes hand, foot and mouth disease in humans and generally effects children. Most of the kids stricken in Cambodia have been under 3 years old.
WHO said in a written statement that some cases turned up other ailments as well, but no evidence of the SARS or H1N1 influenza viruses was detected.
The agency said hand, foot and mouth disease is usually the result of the coxsackievirus A16 virus and is generally mild. EV-71, however, can lead to serious complications.