The patients presented with fever, neurological and respiratory signs, WHO added. There is an investigation currently underway.
Most of the patients are under three years of age, and mainly from southern and central Cambodia. Many of them have been admitted to Kantha Bopha Children's hospital, Phnom Penh, a reference pediatric hospital.
The Ministry of Health of Cambodia says that many of the kids died within 24 hours, despite all efforts.
Samples have been sent to the Institut Pasteur, Cambodia, for testing. So far, they have all come back negative for influenza viruses, including H5N1 (avian influenza, bird flu), SARS (severe acute respiratory syndrome), and Nipah. Nipah is a virus that infects pigs and can be passed onto humans who have been in close contact with infected pigs. It can cause life-threatening encephalitis (brain inflammation).
Cambodian health officials say they were first alerted to this outbreak by Kantha Botha Children's hospital. The Health Ministry then notified WHO through the International Health Regulations (IHR) notification mechanism. In this case, the criteria for notification was met, because the disease agent was not identified, and neither was its mode of transmission.
WHO informs that other disease are also being investigated, including Chikungunya, hand-foot-mouth, and dengue - all illnesses which are currently prevalent in the country.
National and local authorities in Cambodia are telling parents to seek medical help if they identify any unusual signs and symptoms in children. A "good-hygiene awareness campaign" has also been stepped up.
Dr. Ly Sovann, deputy director of communicable disease control department at the Cambodian Ministry of Health, said:
"The investigation is ongoing. We are looking at detailed information from the hospital records and analyzing each and every case. We hope to have a better picture in the coming days."
WHO says it has responded and is working with the Ministry and other partners. Together they are investigating this mystifying outbreak - the aim is to identify the cause and the source of the illness. Most experts believe this outbreak has one cause, and is not a case of different illnesses.
Cambodia - general health dataAccording to WHO, quality of life in Cambodia over the last ten to fifteen years has improved considerably:
- Life expectancy in 2010 was 60 years for men and 65 years for women, up from 49.8 and 46.8 respectively in 1999.
- Cambodia has a mixture of both public and private health service providers and practitioners.
- 5.8% of Cambodia's GDP (gross domestic product) is spent on health
- The country's infant mortality rate dropped from 115 per 1,000 live births in 1993 to 54 per 1,000 in 2009.
- Under-five mortality dropped from 181 per 1,000 live births to 115 from 1993 to 2009.
- 22.9% of children in Ratanakiri, the province with the worst health indicators, die before they reach their fifth year.
- It is the 3rd most landmined country worldwide. Over 60,000 people have been killed because of land mines since 1970 - many, many more have been injured or maimed. Most of the victims were children when the mines exploded.
The Kingdom of Cambodia is in South East Asia in the Indochina peninsula, and borders Vietnam and Thailand