July 25, 2024

WHO Reports First Human Case of Avian Influenza A (H5N1) in Chile Due to Environmental Exposure

The 151st session of the Executive Board on 30 May 2022. This second shorter meeting of the year is a follow-up to the World Health Assembly. The Executive Board is composed of 34 technically qualified members elected for three-year terms. The main functions of the Board are to implement the decisions and policies of the Health Assembly, and advise and generally to facilitate its work.

According to the World Health Organization (WHO), a human in Chile has been diagnosed with avian influenza A (H5N1). The patient, a 53-year-old man from the Region of Antofagasta, did not have any pre-existing medical conditions or recent travel history. It is believed that he contracted the virus through environmental exposure due to the large number of dead sea mammals and wild birds found in the vicinity of his home.

The patient started experiencing symptoms on March 13, including a cough, sore throat, and hoarseness. He went to a local hospital on March 21 and was later transferred to a regional hospital on March 22 due to his worsening condition. He was then admitted to the intensive care unit, where he remains under close supervision and mechanical ventilation because of pneumonia.

The case was detected through routine severe acute respiratory infection (SARI) surveillance, with a negative SARS-CoV-2 result from a nasopharyngeal swab collected by reverse transcription-polymerase chain reaction (RT-PCR) test. A bronchoalveolar sample was collected on March 27 and tested positive for an unsubtypeable influenza A virus by PCR, which was later confirmed as avian influenza A(H5N1) on March 29.

The Chilean Institute of Public Health completed genomic sequencing on April 5, which identified avian influenza virus A(H5N1) phylogenetic clade 2.3.4.4b. The genomic sequencing had a 99.9% match with H5 hemagglutinin sequences from Chilean birds, and complete neuraminidase (NA) had a 100% match with N1 sequences from Chilean birds.

A total of 12 close contacts, including healthcare workers, were identified and tested negative for influenza. They have completed the monitoring period, and no further cases in Chile have been identified so far.

Avian influenza infection in humans can cause severe disease and is notifiable under the International Health Regulations (IHR, 2005). The WHO is collaborating closely with the Ministry of Health of Chile to provide technical support and guidance for the public health response, including infection prevention and control measures, clinical management, and contact tracing.

Avian influenza A (H5N1) was first detected in the Region of the Americas in birds in December 2014. Highly pathogenic avian influenza (HPAI) has been detected in wild aquatic birds, pelicans, penguins, and sea lions in the Antofagasta Region between December 2022 and February 2023.

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