A deadly form of a common childhood illness has been linked to the mysterious child deaths in Cambodia that sparked alarm after a cause could not immediately be determined, Cambodian health officials said Monday.

Lab tests have confirmed that a virulent strain of hand, foot and mouth disease known as EV-71 is to blame for some of the 59 cases reviewed since April, including 52 deaths, according to a joint statement from the World Health Organization and the Cambodian Health Ministry.

The numbers were lowered from the initial report of 62 cases.