Cambodian children and their parents sitting at Kantha Bopha children's hospital in Phnom Penh. Medical experts are scrambling to respond to what the Cambodian health ministry and World Health Organization have labelled an "undiagnosed syndrome" that has claimed the lives of at least 56 boys and girls since April. Photograph: AFP PHOTO / Khem Sovannara

Doctors have made a breakthrough in their efforts to identify the unknown and deadly illness that has claimed the lives of dozens of Cambodian children over the past four months.

Enterovirus 71, commonly associated with Hand, Foot and Mouth disease, has been singled out by virologists at Institut Pasteur as the explanation of the outbreak, according to emails from the head of the non-profit institute’s virology unit to the Ministry of Health and Kantha Bopha Children’s Hospital doctors sent on Friday and obtained by the Post yesterday.

HFM is endemic in Vietnam and virologists homed in on the EV71 strain after adapting investigative testing to detect recent mutations of the virus that have appeared in Cambodia’s neighbour.

World Health Organization epidemiologist Dr Nima Asgari said the findings had “demystified” the situation, but added that they are “still looking at the clinical picture”.

Institut Pasteur had tested 24 samples and found 15 exhibited EV71.

“[These results will be further investigated] in the next few days, and then we can say whether a significant majority of these patients had EV71,” Asgari said.

WHO country director Dr Pieter Van Maaren said the strain had not been easy to diagnose and that the investigation was ongoing.

“There is no immediate need for a travel advisory, and WHO has not planned anything as of today,” Van Maaren said, qualifying his remarks with the still-evolving understanding of the illness that the WHO and Ministry of Health say has killed 56 children.

However, Kantha Bopha, which first alerted the ministry of the outbreak, said in a statement yesterday that 64 children had died from the illness in their hospitals alone.

“[Children] develop in the last hours of their life a total destruction of the alveolus in the lungs,” founding doctor Beat Richner said of the atypical EV71 symptom in a statement yesterday.

“Still, we have yet to see what is really causing the deadly pulmonary complication and see if a toxic factor is playing a role too,” added Richner, who remains concerned the deaths may be triggered by maltreatment and drug intoxication in private clinics.

Minister of Health Mam Bunheng said that even though EV71 was not a new disease, it had taken officials a while to “investigate thoroughly before we reveal publicly”.

“All people in Cambodian should be aware of good hygiene,” he added.

Ministry of Health officials said yesterday they were continuing to call on families to exercise good hygiene practices and to report all suspicious illness involving fever to hospitals.

“If children get fever and have a skin rash, please send them to hospital,” Ly Sovann, deputy director of the communicable disease department, said.

EV71 can cause severe complications of HFM disease including neurological, cardiovascular and respiratory problems and fatal cases of encephalitis.

No specific anti-viral therapy is available for EV71, however, the risk of infection is lowered significantly with high standards of personal and environmental hygiene, according to information on the virus published on the WHO website.

In 2011, there was an outbreak of HFM disease in Vietnam that had 98 fatalities.

However, that outbreak was associated with 42,673 non-fatal cases, a much lower mortality rate than appears in Cambodia’s outbreak.

WHO’s Asgari said initial reports of outbreaks would be of the sickest people and were bound to appear to have a higher mortality rate.

“Once you find the disease, you can do the investigation in the community and find there is a whole spectrum of the disease,” he said. “There will be milder cases, a bigger denominator with a lower percentage of mortality.”

Asgari said he personally had never heard of EV71 appearing in Cambodia before.

In Cambodia, according the Ministry of Health and the WHO, out of 74 cases, 56 were fatal.

According to Kantha Bopha, the figure is 66 cases, with 64 fatalities.

To contact the reporters on this story: Bridget Di Certo at [email protected]

Chhay Channyda at [email protected]