Recently, there have been a rash of stories in the news covering a mysterious disease that has appeared in Cambodia, killing over 50 children in the last few months. Currently, there is evidence that this disease is caused by enterovirus 71, a causative agent of hand, foot, mouth disease. What is interesting is that these children are presenting with symptoms more severe than foot-and-mouth that include encephalitis, high fever, difficulty breathing, and eventual destruction of the alveoli of the lungs leading to death. This is an unusual presentation of enterovirus infection, as this usually causes a mild illness that does not result in hospitalization. However, EV71 has been known to cause neurological disease in the past and would explain the symptoms experienced by patients in this outbreak.
So why did this outbreak start? Why would a virus that normally causes a mild disease kill so many children?My personal theory is that this virus was not endemic in Cambodia prior to this outbreak. What we in fact may be seeing it the “iceberg effect” where only the most severe cases are reported while the majority of those are asymptomatic. Enteroviruses have very similar routes of transmission as poliovirus and both are members of the Picornaviridae family. Months ago there was a large naive population in Cambodia that had never before seen this virus and as a result of low herd immunity and high communicability this virus spread through the population rapidly. It is possible that many thousands of people have been infected and what we are seeing is just the tip of the iceberg. In this particular case the apex of the iceberg is children presenting with severe neurological disease, fever, and extensive lung pathology which can be fatal. What we don’t see are the majority of asymptomatic cases and as a result we focus on those that are obvious, making it appear that the disease is much more pathogenic and lethal than it actually is.
It is my sincere hope that these cases are the major peak of the outbreak and that we see fewer and fewer children contracting this disease as new infections fall. Knowing the virus responsible for this disease is a major step towards understanding how to handle this outbreak from a public health standpoint.
Links: Cambodia’s Outbreak Linked to Hand, Foot, Mouth Virus -Business Week
Cambodian deaths tied to deadly form of common childhood illness – Recordonline.com