The outbreak appears to have been caused by enterovirus 71.
In early July 2012, an outbreak of severe illness with high mortality was reported by the Ministry of Health in Cambodia. According to a WHO report dated July 13, 78 cases in 14 provinces had been identified since April, mostly in children aged ❤ years.
Investigation focused on the 61 children who met the case definition, of whom 54 had died. Illness manifestations included respiratory symptoms, fever, and generalized neurological abnormalities; children who died usually did so within 24 hours after hospital admission. Samples from 31 patients were tested for a variety of pathogens by Institut Pasteur du Cambodge, and “most” tested positive for enterovirus 71 (EV-71); a few also tested positive for dengue virus or Streptococcus suis. On July 15, 2012, authorities announced that no additional cases had been noted in Cambodia. Investigators believed that the use of steroids, which can suppress the immune system, worsened the illness in many of the patients.
Comment: EV 71 — a member of the picornavirus family — was first isolated in the late 1960s. It has been associated with outbreaks worldwide, most recently in Asia. Infection with EV 71, like that with other enteroviruses, ranges from asymptomatic to lethal and can manifest as rashes, diarrhea, respiratory symptoms, meningitis, hand-foot-mouth disease (HFMD), or myocarditis. Less commonly, it has been associated with acute flaccid paralysis, encephalitis, Guillain-Barré syndrome, and pulmonary edema and hemorrhage.
HFMD is most often caused by coxsackievirus A16 (another enterovirus) but is also caused by EV 71. According to the WHO, HFMD usually begins with fever, poor appetite, malaise, and sore throat. One or 2 days after fever onset, painful sores develop on the tongue, gums, and inside of the cheeks, beginning as small red blistering spots and then often becoming ulcers. A nonitchy skin rash develops over 1 or 2 days, with flat or raised red spots that may blister. Usually located on the palms of the hands and soles of the feet, the rash can also appear on the buttocks or genitals. Generally, HFMD is spread from person to person by direct contact with nose or throat discharges, saliva, fluid from blisters, or stool of infected persons. Transmissibility is greatest during the first week of the illness but can last for several weeks. No vaccine or antiviral agent has proven effective in preventing or treating EV 71 infection.