Human Exposures to H5N6 Avian Influenza, England, 2018

Pilot of asymptomatic swabbing of humans following exposures to confirmed avian influenza A(H5) in avian species in England, 2021/2022

A programme of asymptomatic swabbing was piloted in 2021/2022 in England to further understand the risk of human infection with avian influenza in exposed individuals and to evaluate this surveillance approach as a public health measure. There were challenges in deploying this pilot that will need to be addressed for future seasons. However, there was one detection of avian influenza A(H5N1) in a human despite low uptake in eligible exposed persons. Future use of asymptomatic swabbing could help provide an evidence base to quantify asymptomatic infection, quickly identify signals of increased animal to human transmission and improve public health preparedness.

WITHDRAWN: Molecular Evolution and Amino Acid Characteristics of Main Antigen Genes of Clinical Duck-Derived H5N6 Subtype Avian Influenza Virus in East China from 2015 to 2019

This article has been withdrawn at the request of the authors. The Publisher apologizes for any inconvenience this may cause.

Genetic diversity, phylogeography, and evolutionary dynamics of highly pathogenic avian influenza A (H5N6) viruses

From 2013 onwards, the spread of novel H5N6 highly pathogenic avian influenza (HPAI) viruses in China has posed great threats to not only poultry industry but also human health. Since late-2016 in particular, frequent outbreaks of clade 2.3.4.4 H5N6 HPAI viruses among wild birds have promoted viral dissemination in South Korea, Japan, and European countries. In response to those trends, we conducted molecular genetic analysis of global clade 2.3.4.4 H5N6 viruses in order to characterize spatio-temporal patterns of viral diffusion and genetic diversity among wild birds and poultry. The clade 2.3.4.4 H5N6 viruses were classified into three groups (Group B, C, and D). During the cocirculation of Group C/D H5N6 viruses from 2013 to 2017, viral movements occurred between close or adjacent regions of China, Vietnam, South Korea, and Japan. In addition, viral migration rates from Guangdong and Hunan to multiple adjacent provinces seemed to have been highly supported by transmission routes (Bayes factors >100), suggesting that southern China was an epicenter for the spread of H5N6 viruses in poultry during that period. Since the introduction of H5N6 viruses originating in wild birds in late-2016, evolving H5N6 viruses have lost most previous genotypes (e.g. G1, G2, and G1.2), whereas some prevailing genotypes (e.g. G1.1, G1.1.b, and G3) in aquatic birds have been dominated, and in particular, the effective population size of H5N6 originating in wild birds dramatically increased; however, the population size of poultry-origin H5N6 viruses declined during the same period, indicating that wild bird migration might accelerate the genetic diversity of H5N6 viruses. Phylogeographic approaches revealed that two independent paths of H5N6 viruses into South Korea and Japan from 2016 to 2018 and provided evidence of Group B and Group C H5N6 viruses were originated from Europe and China, respectively, as regions located in the East Asia-Australian migration flyway, which accelerated the genetic variability and dissemination. Altogether, our study provides insights to examine time of origin, evolutionary rate, diversification patterns, and phylogeographical approach of global clade 2.3.4.4 H5N6 HPAI viruses for assessing their evolutionary process and dissemination pathways.

Avian influenza overview August - November2019

Between 16 August and 15 November 2019, one low pathogenic avian influenza (LPAI) A(H5) outbreak in poultry in France was reported in Europe. Genetic characterisation reveals that the virusclusterswith Eurasian LPAI viruses. No highly pathogenic avian influenza (HPAI) outbreaks in birds were notified in Europe in the relevant period for this report. HPAI A(H5N6) viruswas identified in chickens in Nigeria, this isthe first report of HPAI A(H5N6) from the African continent.FewerHPAI outbreaks in Asia and Africa were reported during the time period for this report compared with the previous reporting period. Apart from the long‐term epidemic of HPAI A(H5N2)in Taiwan, only six HPAI outbreakswere reported in domestic birds from Nepal, South Africa and Taiwan. Furthermore, no HPAI detections fromwild birds were reported worldwide in the relevant time period forthis report.Even if the risk of incursion of HPAI from wild birds into poultryestablishments in Europe is currently assessed as low, it is important to maintain passive surveillance activities. The focus should be on wild bird species that are in the revised list of target species in order to detect any incursion of HPAI virus early and initiate a warning.Despite the decrease in the number of avian influenza outbreaks over recent months, it is important to maintain a high alert level andhigh standard of biosecurity onpoultry establishments.In Europe, no human infections due toHPAI viruses detected in wild bird or poultry outbreaks, have been reported. The risk of zoonotic transmission to the general public in Europe is considered to be very low.

Pandemic potential of highly pathogenic avian influenza clade 2.3.4.4 A(H5) viruses

The panzootic caused by A/goose/Guangdong/1/96‐lineage highly pathogenic avian influenza (HPAI) A(H5) viruses has occurred in multiple waves since 1996. From 2013 onwards, clade 2.3.4.4 viruses of subtypes A(H5N2), A(H5N6), and A(H5N8) emerged to cause panzootic waves of unprecedented magnitude among avian species accompanied by severe losses to the poultry industry around the world. Clade 2.3.4.4 A(H5) viruses have expanded in distinct geographical and evolutionary pathways likely via long distance migratory bird dispersal onto several continents and by poultry trade among neighboring countries. Coupled with regional circulation, the viruses have evolved further by reassorting with local viruses. As of February 2019, there have been 23 cases of humans infected with clade 2.3.4.4 H5N6 viruses, 16 (70%) of which had fatal outcomes. To date, no HPAI A(H5) virus has caused sustainable human‐to‐human transmission. However, due to the lack of population immunity in humans and ongoing evolution of the virus, there is a continuing risk that clade 2.3.4.4 A(H5) viruses could cause an influenza pandemic if the ability to transmit efficiently among humans was gained. Therefore, multisectoral collaborations among the animal, environmental, and public health sectors are essential to conduct risk assessments and develop countermeasures to prevent disease and to control spread. In this article, we describe an assessment of the likelihood of clade 2.3.4.4 A(H5) viruses gaining human‐to‐human transmissibility and impact on human health should such human‐to‐human transmission occur. This structured analysis assessed properties of the virus, attributes of the human population, and ecology and epidemiology of these viruses in animal hosts.

Avian influenza overview November 2019- February2020

Between 16 November 2019 and 15 February 2020, 36 highly pathogenic avian influenza (HPAI) A(H5N8) virus outbreakswere reported in Europe in poultry (n=34), captive birds (n=1) and wild birds (n=2), in Poland, Hungary, Slovakia, Romania, Germany, Czechiaand Ukraine,one HPAI outbreakcaused by a simultaneous infection with A(H5N2) and A(H5N8) was reported in poultry in Bulgaria, andtwo low pathogenic avian influenza (LPAI) A(H5) virus outbreaks were reported in poultryin the United Kingdom and in Denmark. Genomic characterisation of the HPAI A(H5N8) viruses suggests that they are reassortants of HPAI A(H5N8) viruses from Africa and LPAI viruses from Eurasia. It is likely that this reassortment occurred in wild migratory birds in Asia during the summer and then spread to eastern Europe with the autumnmigration. This is the first time that wild bird migration from Africa to Eurasia has been implicated in the long-distance spread of HPAI viruses to the EU. Given the late incursion of HPAI A(H5N8) virus into the EU in this winter season (first outbreak reported on 30 December 2019), its overall restriction to eastern Europe, and the approaching spring migration, the risk of the virus spreadingfurther in the west via wild birds is decreasing for the coming months. Genetic analysis of the HPAI A(H5N2) and A(H5N8) viruses detected in the Bulgarian outbreak reveals that these virusesare both related to the 2018-19 Bulgarian HPAI A(H5N8) viruses and not to the HPAI A(H5N8) viruses currently circulating in Europe.An increasing number of HPAI A(H5N1), A(H5N2), A(H5N5) and A(H5N6) virus outbreaks in poultry in Asia were reported during the time period for this report compared with the previous reporting period. Single outbreaks of HPAI A(H5N8) virus were notified by Saudi Arabia and South Africa. Furthermore, in contrast to the last report, HPAI virus-positive wild birds were reported from Israel and one of the key migration areas in northern China.Two human cases due to A(H9N2) virus infection were reported during the reporting period.

Avian influenza overview February- August 2019

Between 16 February and 15 August 2019, five HPAI A(H5N8) outbreaks at poultry establishments in Bulgaria, two low pathogenic avian influenza (LPAI) A(H5N1) outbreaks in poultry in Denmark and one in captive birds in Germany, one LPAI A(H7N3) outbreak in poultry in Italy and one LPAI A(H7N7) outbreak in poultry in Denmark were reported in Europe. Genetic characterisation reveals that viruses from Denmark cluster with viruses previously identified in wild birds and poultry in Europe; while the Italian isolate clusters with LPAI viruses circulating in wild birds in Central Asia. No avian influenza outbreaks in wild birds were notified in Europe in the relevant period for this report. A decreased number of outbreaks in poultry and wild birds in Asia, Africa and the Middle East was reported during the time period for this report, particularly during the last three months. Furthermore, only six affected wild birds were reported in the relevant time period of this report. Currently there is no evidence of a new HPAI virus incursion from Asia into Europe. However, passive surveillance systems may not be sensitive for early detection if the prevalence or case fatality in wild birds is very low. Therefore, it is important to encourage and maintain passive surveillance in Europe encouraging a search for carcasses of wild bird species that are in the revised list of target species in order to detect any incursion of HPAI virus early and initiate warning. No human infections due to HPAI viruses - detected in wild birds and poultry outbreaks in Europe - have been reported during the last years and the risk of zoonotic transmission to the general public in Europe is considered very low.