First Human Influenza A(H5N1) (Bird Flu) Virus Infections in Cambodia Reported for 2024
February 12, 2024 — Cambodia has reported four recent human infections with highly pathogenic avian influenza (HPAI) A(H5N1) (bird flu) virus. These are the first human infections with HPAI A(H5N1) virus identified in Cambodia in 2024. The four infections occurred in three children, one of whom died, and an adult, all of which were identified in late January and early February. All patients reportedly had a history of recent exposure to sick or dead poultry prior to their illness. Currently, there is no indication of person-to-person spread associated with these four cases of H5N1 virus infection in Cambodia, and they are not thought to pose a threat to the health of the U.S. public.
The first two patients were epidemiologically unrelated and were admitted to different hospitals in Cambodia; they both recovered and were discharged home. The third patient died shortly after transfer to a pediatric hospital in the capital, and the fourth patient was admitted for monitoring and treatment. The third and fourth patients are siblings but lived in different villages; dead poultry were brought from the household of the fourth patient to the household of the third patient, and both siblings were exposed. Investigations are ongoing to monitor their close contacts and to identify any additional infections. The U.S. CDC is working closely with the Ministry of Health’s Cambodia Communicable Disease Control (C-CDC) Department, the National Institute of Public Health in Cambodia (NIPH), the Ministry of Agriculture, Forestry and Fisheries, Institut Pasteur du Cambodge (IPC), the World Health Organization, the United States Agency for International Development, the Food and Agriculture Organization, and the Wildlife Conservation Society of Cambodia in a One Health approach to respond to these sporadic human infections.
Genetic sequencing of the first and third patients’ specimens by IPC and NIPH identified both H5N1 viruses as H5 clade 2.3.2.1c, which has circulated in Cambodia among birds and poultry for many years. This H5 virus clade 2.3.2.1c in Cambodia is different from the H5N1 virus that has caused wild bird and poultry outbreaks in the United States (clade 2.3.4.4b) and other countries. Genetic sequencing of the fourth patient’s specimens is in process.
Six sporadic human infections with HPAI A(H5N1) bird flu virus occurred in Cambodia last year (February, October, and November 2023). Additional sporadic human infections are not unexpected in people with direct or close unprotected exposures to sick or dead poultry infected with HPAI A(H5N1) virus in areas with endemic spread among poultry. Four of the six human infections with HPAI A(H5N1) viruses in Cambodia during 2023 were fatal.
More information on H5N1 bird flu in the United States and globally:
Technical Report: Highly Pathogenic Avian Influenza A(H5N1) Viruses (cdc.gov)
Previous reports of H5N1 bird flu in Cambodia:
Update on H5N1 Bird Flu in Cambodia (cdc.gov)
H5N1 Update: Two Human H5N1 Cases in Cambodia | Avian Influenza (Flu) (cdc.gov)
