#18,499
Today FAO/WHO/WOAH released an updated assessment of the threat posed by HPAI H5, and while they currently gauge the public health impact of such infections globally as minor, a couple of caveats are in order.
- First, this is based on information received by these agencies as of Nov 18th;
- Second, it is based on what is being reported by member nations, which history has shown not always to be complete or timely.
Updated joint FAO/WHO/WOAH public health assessment of recent influenza A(H5) virus events in animals and people
Assessment based on data as of 18 November 2024
20 December 2024
Key points
At the present time, based on available information, FAO-WHO-WOAH assess the global public health risk of influenza A(H5N1) viruses to be low, while the risk of infection for occupationally exposed persons is low to moderate depending on the risk mitigation measures in place and the local avian iwork with national agencies and partners to better understand the exposure to and risk from raw/unpasteurized milk and milk product nfluenza epidemiological situation. Transmission between animals continues to occur and, to date, a growing yet still limited number of human infections are being reported. Although additional human infections associated with exposure to infected animals or contaminated environments are expected to occur, the overall public health impact of such infections at a global level, at the present time, is minor.
This risk assessment from FAO, WHO, and WOAH updates the assessment of the risk of zoonotic transmission (for example, animal to human) considering additional information made available since the previous assessment of 14 August 2024. This update is limited to the inclusion of additional information being made available globally.
Due to the potential risk to human health and the farreaching implications of the disease on the health of wild birds, poultry, livestock and other animal populations, the use of a One Health approach is essential to tackle avian influenza effectively, to monitor and characterize virus circulation, to prevent within species and to new species transmission, to reduce spread among animals, and to prevent human infections from exposure to animals.
(SNIP)
Detections in humans
Since the last joint assessment of August 2024 and as of 27 November 2024, an additional 49 human cases of infection with A(H5) viruses have been reported. Of these, 45 were reported from the USA: 28 in persons with exposure to A(H5N1)-infected dairy cattle in California, 15 in persons with exposure while involved in depopulation of A(H5N1)-infected commercial poultry farms, and two in persons with unknown exposure at the time of reporting. Samples from three cases related to poultry depopulation in the State of Colorado were confirmed to contain A(H5N1) clade 2.3.4.4b, genotype B3.13, virus while cases related to poultry depopulation in the State of Washington contained viruses belonging to the D1.1 genotype.
Intensive epidemiological investigation of the case with unknown exposure in the State of Missouri could not identify any animal or animal product exposure. Five health care workers in contact with the case were shown to be A(H5N1) seronegative, the case and one household contact who reported symptoms with the same onset date were weakly A(H5N1) seropositive. The timing of symptom onsets supports a single common exposure, which at present remains unknown, rather than human-to-human transmission.32
All but one of the detected cases in the USA have reported mild symptoms, including conjunctivitis and mild respiratory symptoms, and recovered without hospitalization. The one exception who had comorbidities reported gastrointestinal symptoms and was hospitalized.33,34
A recent sero-study in 115 persons in Colorado and Michigan working on dairy farms during A(H5N1) outbreaks among dairy cattle found that eight (7.0%) had serologic evidence of recent infection(seropositive, ≥40 antibody titres to H5 2.3.4.4b by both micro-neutralization and hemagglutination inhibition assays). These seropositive individuals reporting working with dairy cattle or in the milking parlour, and four reported being ill when A(H5) was detected among the dairy cattle.35
work with national agencies and partners to better understand the exposure to and risk from raw/unpasteurized milk and milk productThree human cases of clade 2.3.2.1c A(H5N1) virus infection were reported from Cambodia since the last update of August 2024. All were hospitalized; two recovered and the other died. All three cases had exposure to sick or dead backyard poultry.
On 13 November, one human case of domestically acquired A(H5N1) infection was confirmed by Canadian authorities in a young person without underlying conditions. The condition of the case was reported as critical. There are several ongoing investigations to better understand the exposures of this case, and so far investigations have not been able to identify the source of exposure. The virus from the case belonged to clade 2.3.4.4b, specifically the D1.1 genotype, which was similar to viruses concurrently affecting poultry in the region.36
(SNIP)
Recommended actions
It is recommended that Member States and national authorities:
• increase surveillance and vigilance, in human populations, especially amongst occupationally exposed persons, for the possibility of zoonotic infections, particularly through National Influenza Centres (NICs) and other influenza laboratories associated with GISRS;
• assess and reduce the risk among occupationally exposed persons using methods such as active case finding and molecular and serologic methods, reducing environmental exposures, providing adequate and appropriate personal protective equipment;
• conduct active case finding around suspected and confirmed human cases to determine if there are additional cases or indications of human-to-human transmission; and
• work with national agencies and partners to better understand the exposure to and risk from raw/unpasteurized milk and milk product
Under the International Health Regulations (IHR) (2005),55 States Parties are required to notify WHO within 24 hours of any laboratory-confirmed case of human influenza caused by a new subtype according to the WHO case definition. 56 WHO has published the case definition for human infections with avian influenza A(H5) virus requiring notification under IHR (2005).
