Chile has reported the first case of avian influenza A(H5N1), a highly pathogenic virus that mainly affects birds but can also infect humans in rare cases. The patient, a 53-year-old male from the Region of Antofagasta, developed symptoms on March 13, 2023, and was admitted to the intensive care unit on March 23.
The virus’s phylogenetic clade 2.3.4.4b closely resembles Chilean birds, and the most probable mode of transmission was through environmental exposure. The patient is currently in respiratory isolation under multidisciplinary management, with mechanical ventilation due to pneumonia.
The World Health Organization (WHO) suggested Healthcare authorities promptly notify any human cases of avian influenza to enable immediate public health actions, including timely investigation and response to prevent further transmission.
Since the first confirmation of avian influenza A(H5N1) in the Region of the Americas in 2014, three human infections caused by avian influenza A(H5) have been reported. The Region of the Americas has seen an increasing number of highly pathogenic avian influenza A(H5) outbreaks in backyard and farm poultry, wild birds, and wild mammals during 2022 and 2023.
Globally, 873 human infections with A(H5N1) viruses have been reported to the World Health Organization (WHO) since 2003, resulting in 458 deaths. The likelihood of human-to-human spread of A(H5) viruses, including H5N1, is low as the virus has yet to acquire the ability for sustained transmission among humans. However, people should avoid contact with sick or dead animals from unknown causes and report the occurrence to the authorities.
The Ministry of Health of Chile, the Agricultural and Livestock Service (SAG), and the National Fisheries and Aquaculture Service of Chile (SERNAPESCA) are conducting intersectoral activities to follow up on the avian influenza outbreaks in Antofagasta Region and other regions.
Active monitoring of persons with respiratory symptoms and exposure to wild birds, poultry, and sea mammals is being undertaken. Seasonal influenza vaccination is being conducted in risk groups according to the guidelines of the National Immunization Program. The public has been informed about this case and prevention measures through messaging for different target audiences.
The WHO highlights the significance of worldwide monitoring to identify and track virological, epidemiological, and clinical variations linked with emerging or circulating influenza viruses that could potentially harm human or animal health. It also stresses the importance of promptly sharing virus samples for risk assessment.
Given the range of zoonotic influenza viruses that have caused human illnesses, heightened surveillance is necessary in both animal and human populations, and all zoonotic infections must be thoroughly investigated. Additionally, pandemic preparedness planning is critical. The WHO recommends vaccinating poultry workers with the seasonal influenza vaccine to prevent a viral mutation that might make human-to-human transmission easier.
The emergence of avian influenza A(H5N1) in Chile highlights the importance of continued surveillance and public health preparedness for emerging infectious diseases. Healthcare professionals should maintain a high index of suspicion for avian influenza when patients with severe respiratory disease have a history of exposure to sick or dead birds. Timely measures must be implemented to prevent further transmission and minimize the pandemic risk.
