#17,392
Eight days ago Chile became the second South American nation to report a human infection with HPAI H5, reportedly in a 53 year old man from Antofagasta region, who remains hospitalized (and on a mechanical ventilator) with severe pneumonia.
Details remain scant, and while it has been assumed that the virus is the H5N1 strain circulating across both North and South America, today WHO states that its neuraminidase type and clade information have not been firmly established.
Samples have reportedly been sent to both the CDC and the WHO for further analysis.
There is also some ambiguity over how this individual was exposed, although environmental contamination, likely from birds or marine mammals, is considered a possibility.
So far, none of his contacts have tested positive for avian influenza, but yesterday one of them reportedly developed respiratory symptoms, and will be further monitored.
I've only posted some excerpts from the WHO report, so follow the link to read it in its entirety.
Human infection caused by Avian Influenza A (H5) - Chile
6 April 2023
Situation at a glance
On 29 March 2023, the Ministry of Health of Chile notified WHO of a laboratory-confirmed case of human infection caused by avian influenza A(H5) virus in the Region of Antofagasta. This is the first human infection with avian influenza A(H5) virus reported in Chile and the third reported in the Region of the Americas to date. This is a single human infection and there is currently no evidence of the disease spreading among humans. An outbreak investigation is ongoing including determining the exposure of the case to the virus. In recent months of 2023, unprecedented outbreaks of highly pathogenic avian influenza (HPAI) A(H5N1) in animals have been reported from Chile. Avian Influenza A(H5N1) viruses have been detected among backyard poultry, farm poultry, wild birds, and sea mammals.
Avian influenza infection in a human can cause severe disease and is notifiable under the International Health Regulations (IHR, 2005)[1].
Description of the case
On 29 March 2023, the Ministry of Health of Chile notified WHO of the detection of human infection with avian influenza A(H5) virus, confirmed by the Institute of Public Health of Chile (ISP per its acronym in Spanish), which is the National Influenza Centre. The patient is a 53-year-old male from the Region of Antofagasta in the north of Chile. He had no history of comorbidities or recent travel.
On 13 March 2023, he developed symptoms including cough, sore throat, and hoarseness. On 21 March, due to worsening symptoms, he sought care at a local hospital. On 22 March 2023, the case developed dyspnea and was admitted to a Regional Hospital at Antofagasta. A nasopharyngeal swab sample was collected as part of routine severe acute respiratory infection (SARI) surveillance and tested negative for COVID-19 by reverse transcription-polymerase chain reaction (RT-PCR). On 23 March, he was admitted to the intensive care unit. On 24 March, treatment with antivirals (oseltamivir) and antibiotics was initiated. He remains in respiratory isolation under multidisciplinary management, with mechanical ventilation due to pneumonia.
On 27 March, a bronchoalveolar sample was collected and tested positive for an unsubtypeable influenza A virus by RT-PCR. The sample was sent to the ISP and tested positive for avian influenza A(H5) on 29 March. The neuraminidase type is yet to be confirmed and the clade information for the avian influenza A(H5) virus detected in this human case is not yet known. The NIC has forwarded the patient's samples to a WHO Collaborating Centre for further characterization.
Three close contacts of the case were asymptomatic and tested negative for influenza and have concluded the monitoring period. Additionally, a total of nine contacts among health care workers were identified, all concluded the monitoring on 4 April, however on 5 April one of them developed respiratory symptoms, therefore, further testing is ongoing, and the period of monitoring was extended for 7 more days for this contact of the case.
Avian influenza A (H5N1) was first detected in the Americas in birds in December 2014. Between December 2022 and February 2023, highly pathogenic avian influenza (HPAI) was detected in wild aquatic birds (pelicans and penguins) and sea mammals (sea lions) in the Antofagasta Region where the case resides. According to preliminary findings of the epidemiological investigation of this human case, the most plausible route of transmission was through environmental exposure in areas close to the residence of the case where either sick or dead sea mammals or wild birds were found.
Epidemiology of disease
Zoonotic influenza infections in humans may range from asymptomatic or mild upper respiratory infection (fever and cough) to rapid progression to severe pneumonia, acute respiratory distress syndrome, shock, and death, depending on factors related to the virus and the host. Rarely, gastrointestinal, or neurological symptoms have been reported. Human cases of avian influenza are usually the result of direct or indirect exposure to infected live or dead poultry or contaminated environments.
In the Region of the Americas during 2022 and 2023, an increasing number of outbreaks of highly pathogenic avian influenza A(H5) have been reported in backyard poultry, farm poultry, wild birds, and wild mammals. Since the first confirmation of avian influenza A(H5N1) in the region in 2014, three human infections caused by avian influenza A(H5) have been reported: the first in the United States of America, reported in April 2022; the second in Ecuador, reported in January 2023; and this case. Globally, since 2003, 873 human infections, including 458 deaths (CFR 52%), with A(H5N1) viruses have been reported to WHO. Additionally, three human infections with influenza A (H5[2]) viruses, 84 human cases of infection with A(H5N6) viruses, and seven human cases of infection with A(H5N8) viruses have been reported to WHO.
Public health response
- Local authorities are carrying out an epidemiological investigation and conducting contact tracing amongst family members and healthcare workers.
- Intersectoral activities have been carried out by the Ministry of Health of Chile, the Agriculture and Livestock Service of the Ministry of Agriculture of Chile, and the National Fisheries and Aquaculture Service of Chile, among others, in order to follow up on the avian influenza outbreaks in the area.
- Active follow-up is being conducted of persons with respiratory symptoms and exposure to wild birds, poultry, and mammals; as well as cases with suspected influenza due to contact with poultry or who have been exposed to birds.
- Seasonal influenza vaccination is being conducted in risk groups according to the guidelines of the National Immunization Program.
- The population has been informed, through messaging for different target audiences, about the case and about prevention measures.
WHO risk assessment
According to the preliminary findings of the local epidemiological investigation, the most plausible hypothesis about transmission is that it occurred through environmental exposure to areas where either sick or dead birds or sea mammals were found close to the residence of the case. According to the information received thus far, the virus has not been detected in other individuals.
Whenever avian influenza viruses are circulating in poultry, wild birds or mammals, there is a risk for sporadic infection and small clusters of human cases due to exposure to infected animals or contaminated environments.
Public health measures have been implemented by both the human and animal health agencies, including monitoring healthcare workers and other contacts of the laboratory-confirmed case. While further characterization of the virus from this human case is pending, currently available epidemiological and virological evidence suggests that A(H5) viruses have not acquired the capacity for sustained transmission among humans, thus the likelihood of human-to-human spread is low. Based on available information, WHO assesses the risk to the general population posed by this virus to be low.
Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. If this were to occur, further community-level spread is considered unlikely as this virus has not acquired the ability to transmit easily among humans.
The preliminary risk assessment will be reviewed as needed should further epidemiological or virological information become available.
