Avian influenza overview December 2022 – March 2023

Abstract

Between 3 December 2022 and 1 March 2023 highly pathogenic avian influenza (HPAI) A(H5N1) virus, clade 2.3.4.4b, was reported in Europe in domestic (522) and wild (1,138) birds over 24 countries. An unexpected number of HPAI virus detections in sea birds were observed, mainly in gull species and particularly in black-headed gulls (large mortality events were observed in France, Belgium, the Netherlands, and Italy). The close genetic relationship among viruses collected from black-headed gulls suggests a southward spread of the virus. Moreover, the genetic analyses indicate that the virus persisted in Europe in residential wild birds during and after the summer months. Although the virus retained a preferential binding for avian-like receptors, several mutations associated to increased zoonotic potential were detected. The risk of HPAI virus infection for poultry due to the virus circulating in black-headed gulls and other gull species might increase during the coming months, as breeding bird colonies move inland with possible overlap with poultry production areas. Worldwide, HPAI A(H5N1) virus continued to spread southward in the Americas, from Mexico to southern Chile. The Peruvian pelican was the most frequently reported infected species with thousands of deaths being reported. The reporting of HPAI A(H5N1) in mammals also continued probably linked to feeding on infected wild birds. In Peru, a mass mortality event of sea lions was observed in January and February 2023. Since October 2022, six A(H5N1) detections in humans were reported from Cambodia (a family cluster with 2 people, clade 2.3.2.1c), China (2, clade 2.3.4.4b), Ecuador (1, clade 2.3.4.4b), and Vietnam (1, unspecified clade), as well as two A(H5N6) human infections from China. The risk of infection with currently circulating avian H5 influenza viruses of clade 2.3.4.4b in Europe is assessed as low for the general population in the EU/EEA, and low to moderate for occupationally or otherwise exposed people.

High pathogenicity avian influenza A (H5N1) clade 2.3.4.4b virus infection in a captive Tibetan black bear (Ursus thibetanus): investigations based on paraffin-embedded tissues, France, 2022

“…This finding was further confirmed by the phylogenetic analysis performed on the other viral segments, which showed that both strains were closely related to strains circulating in Belgium at that time ( Supplementary Figure 5 ). The whole genome analysis revealed both strains belonged to the AB genotype (H5N1-A/duck/Saratov/29-02/2021-like), the main circulating genotype at that time in Europe [6].…”

“…Thus, the occasions on which mammals have been exposed to the virus have become more frequent in turn. Infection generally occurs following exposure to contaminated feces or water, or animal carcasses [6]. Sporadic infections of wild mammals have been described in the past, but have never been as frequent as in recent years.…”

Serological exposure to influenza A in cats from an area with wild birds positive for avian influenza

“…Reports have confirmed the presence of a high number of positive for the HPAIV H5N1 virus, clade 2.3.4.4b, in Europe between 3 December 2022 and 1 March 2023 (EFSA et al, 2023). In Spain, an outbreak of HPAIV between May 2022 and March 2023 was reported, and the Spanish authorities also reported 100 cases in wild birds and one in poultry (WOAH, 2023).…”

Geographic, ecological, and temporal patterns of seabird mortality during the 2022 HPAI H5N1 outbreak on the island of Newfoundland

“…A wide range of birds and a number of mammalian species have been found to be infected with HPAIVs, though mortality rates depend in part on differences in taxa- and species-specific traits (European Food Safety Authority et al 2023a; Teitelbaum et al 2023; Alkie et al 2023). For example, unusual mortality among dabbling ducks has not been largely attributed to HPAIV despite its detection in apparently healthy birds, though some species of diving ducks, such as Tufted Ducks ( Aythya fuligula ), are particularly susceptible to HPAIVs and often exhibit high mortality rates (Keawcharoen et al 2008; Kleyheeg et al 2017; Caliendo et al 2022).…”