Outbreak Investigation and Response: Two Fatal Cases of Avian Influenza A(H5N1) Detected in Humans in October 2023, Cambodia

In October 2023, Cambodia reported two fatal human cases of influenza A(H5N1) from two provinces. The national and subnational rapid response teams investigated the outbreak to describe its characteristics, identify potential linkages between the cases, assess the outbreak magnitude, understand the local perspective and response. Medical records were reviewed, and contact tracing and active case finding were conducted in the affected areas. Laboratory investigation and environmental survey were performed. Local authorities were interviewed. The two cases, confirmed to have influenza A(H5N1) clade 2.3.2.1c, were a 50-year-old man from Svay Rieng Province and a 2-year-old girl from Prey Veng Province. Both cases had direct contact with sick and dead poultry at their house before developing respiratory symptoms. We identified 65 close contacts and 15 suspected cases who tested negative for influenza A, influenza B and SARS-CoV-2. Inappropriate practices of handling sick and dead poultry and allowing free-roaming backyard poultry within houses were identified in the affected villages. There was no linkage between the two cases and no additional cases were found during the investigation. During the response, there was a lack of awareness about avian influenza among communities and health workers. Appropriate medication (e.g., oseltamivir) should be stockpiled at the district level. A lack of coordination and communication among One Health sector was identified. We recommended promoting a joint multisectoral coordination for investigations, strengthening surveillance systems, increasing avian influenza awareness, allocating resources, and holding daily coordination meetings among stakeholders for effective planning and communication.