Avian influenza overview February- August 2019

Emerging highly pathogenic avian influenza (H5N8) virus in migratory birds in Central China, 2020

Eleven highly pathogenic avian influenza H5N8 viruses (clade 2.3.4.4b) were detected in migratory birds in Central China between November and December 2020, which were highly homologous to strains isolated in Europe from October to December 2020. Phylogenetic analysis indicated that the strains in the study possibly spread from Siberia by migratory birds. In this study, we found H5N8 virus infection in migratory birds could cause severe pathological damage and high viral load in multiple organs.

A Seasonal Cause of Encephalitis: Influenza Virus A (H3N1) Infection

Influenza virus infection can have a range of presentations, from asymptomatic to life-threatening disease. We present the case of a 57-year-old woman with a known history of schizophrenia (controlled with medication) who presented to our emergency department in a coma after experiencing a seizure. She had reported flu-like symptoms in the previous week, which evolved to dyspnoea and altered mental status culminating in seizures and coma. Influenza virus A (H3N1) was identified in the cerebrospinal fluid. Although a rare cause of encephalitis, the influenza virus should be considered in the differential diagnosis, especially during epidemics.

LEARNING POINTS

Influenza virus encephalitis should be considered in some specific settings, such as during pandemics or seasonal epidemics.Altered mental status in a patient with a history of mental disease may be easily dismissed as secondary to prior disease or medication.Although rare, extrapulmonary manifestations of influenza virus infection can be serious and fatal.

Multiple Reassortants of H5N8 Clade 2.3.4.4b Highly Pathogenic Avian Influenza Viruses Detected in South Korea during the Winter of 2020-2021

During October 2020–January 2021, we isolated a total of 67 highly pathogenic avian influenza (HPAI) H5N8 viruses from wild birds and outbreaks in poultry in South Korea. We sequenced the isolates and performed phylogenetic analysis of complete genome sequences to determine the origin, evolution, and spread patterns of these viruses. Phylogenetic analysis of the hemagglutinin (HA) gene showed that all the isolates belong to H5 clade 2.3.4.4 subgroup B (2.3.4.4b) and form two distinct genetic clusters, G1 and G2. The cluster G1 was closely related to the 2.3.4.4b H5N8 HPAI viruses detected in Europe in early 2020, while the cluster G2 had a close genetic relationship with the 2.3.4.4b H5N8 viruses that circulated in Europe in late 2020. A total of seven distinct genotypes were identified, including five novel reassortants carrying internal genes of low pathogenic avian influenza viruses. Our Bayesian discrete trait phylodynamic analysis between host types suggests that the viruses initially disseminated from migratory waterfowl to domestic duck farms in South Korea. Subsequently, domestic duck farms most likely contributed to the transmission of HPAI viruses to chicken and minor poultry farms, highlighting the need for enhanced, high levels of biosecurity measures at domestic duck farms to effectively prevent the introduction and spread of HPAI.

Avian influenza overview August - December 2020

Between 15 August and 7 December 2020, 561highly pathogenic avian influenza (HPAI) virus detections were reported in 15EU/EEA countries and UK in wild birds, poultry andcaptive birds, with Germany (n=370), Denmark (n=65), the Netherlands (n=57) being the most affected countries.The majority of the detections have been reported in wild birds(n=510), primarily in barnacle goose, greylag goose, andEurasian wigeon. Raptors have also been detected infected, particularly common buzzard. The majority of the birds had been found dead or moribund,however, there are also reports ofHPAI virus infection in apparently healthy ducks or geese.A total of 43 HPAI outbreaks were notified in poultry;with signs of avian influenza infection being observed in at least 33 outbreaks;the most likely source of infection was indirect contact with wild birds. Three HPAI virus subtypes, A(H5N8) (n=518), A(H5N5) (n=17) and A(H5N1) (n=6),and four different genotypes were identified, suggesting the occurrence of multiple virus introductions into Europe.The reassortant A(H5N1) virus identified in EU/EEA countries has acquired gene segments from low pathogenic viruses and is not related to A(H5N1) viruses of e.g. clade 2.3.2.1c causing human infections outside of Europe. As the autumn migration of wild waterbirds to their wintering areasin Europe continues, and given the expected local movements of these birds, there is still a high risk of introduction andfurther spread ofHPAI A(H5) viruses within Europe.The risk of virus spread from wild birds to poultry is high and Member States should enforce in 'high risk areas' of their territories the measures provided for in Commission Implementing Decision (EU) 2018/1136.Detection of outbreaks in breeder farms in Denmark, the Netherlands and United Kingdom, highlight also the risk of introduction via contaminated materials (bedding/straw) and equipment.Maintaining high and sustainable surveillance and biosecurityparticularly in high-risk areas is of utmost importance. Two human cases due to zoonoticA(H5N1) and A(H9N2) avian influenza virus infection were reportedduring the reporting period. The risk for the general population as well as travel-related imported human cases are assessed as very low.

Avian influenza overview May - August 2020

Between 16 May and 15 August 2020, seven highly pathogenic avian influenza (HPAI) A(H5N8) virus outbreaks were reported in Europe in poultry, with one outbreak reported in Bulgaria(n=1) andsix in Hungary (n=6) and one low pathogenic avian influenza (LPAI) A(H5N3) virus outbreak was reported in poultry in Italy. All six outbreaks detected in Hungary were secondary outbreaks and seem to be the tail end of the HPAI A(H5N8) epidemic that wasobserved in poultry over the winter and spring in central Europe from December 2019 (n=334).Genetic analysis of the HPAI A(H5N8) viruses isolated during this reporting period from Bulgaria and Hungary did not identify any major changes compared tothe viruses collected in the respective countries during the first months of 2020. This suggests a persistence of the virus in the two countries rather than new introductions via infectedwild birds. HPAI A(H5N8) virus has been detected in poultry and wild birds in western Russia within the reporting period, and as of the middle of September also in Kazakhstan. The presence of HPAI virus in western Russiaand in north Kazakhstan,spatially associated with autumnmigration routes of wild waterbirds, is of concern due to the possible spread of the virus via wild birds migrating to the EU.It is highly recommended thatMember States take appropriate measures to promptly detect suspected cases of HPAI, including increasing biosecurity measures. According to past experiences (2005-2006 and 2016-2017 epidemic waves), the northern and eastern European areas might be at higher risk of virus introduction in the coming autumn-winter seasonand should be the key regions where prompt response measures to early detect the virusshould be set up. One human case due to A(H9N2) avian influenza virus infection was reported during the reporting period.

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.

Regional Transmission and Reassortment of 2.3.4.4b Highly Pathogenic Avian Influenza (HPAI) Viruses in Bulgarian Poultry 2017/18

Between 2017 and 2018, several farms across Bulgaria reported outbreaks of H5 highly-pathogenic avian influenza (HPAI) viruses. In this study we used genomic and traditional epidemiological analyses to trace the origin and subsequent spread of these outbreaks within Bulgaria. Both methods indicate two separate incursions, one restricted to the northeastern region of Dobrich, and another largely restricted to Central and Eastern Bulgaria including places such as Plovdiv, Sliven and Stara Zagora, as well as one virus from the Western region of Vidin. Both outbreaks likely originate from different European 2.3.4.4b virus ancestors circulating in 2017. The viruses were likely introduced by wild birds or poultry trade links in 2017 and have continued to circulate, but due to lack of contemporaneous sampling and sequences from wild bird viruses in Bulgaria, the precise route and timing of introduction cannot be determined. Analysis of whole genomes indicates a complete lack of reassortment in all segments but the matrix protein gene (MP), which presents as multiple smaller clusters associated with different European 2.3.4.4b viruses. Ancestral reconstruction of host states of the hemagglutinin (HA) gene of viruses involved in the outbreaks suggests that transmission is driven by domestic ducks into galliform poultry. Thus, according to present evidence, we suggest the surveillance of domestic ducks as they are an epidemiologically relevant species for subclinical infection. Monitoring the spread due to movement between farms within regions and links to poultry production systems in European countries can help to predict and prevent future outbreaks. The 2.3.4.4b lineage which caused the largest recorded poultry epidemic in Europe continues to circulate, and the risk of further transmission by wild birds during migration remains.

Avian influenza overview February - May 2020

Between 16 February and 15 May 2020, 290highly pathogenic avian influenza (HPAI) A(H5) virus outbreakswere reported in Europe in poultry (n=287), captive birds (n=2) and wild birds (n=1)in Bulgaria, Czechia,Germany,Hungary andPolandand two low pathogenic avian influenza (LPAI) A(H7N1) virus outbreaks were reported in poultry in Italy. 258 of 287 poultry outbreaks detected in Europe were secondary outbreaks, suggesting that in the large majoryty of cases the spread of the virus was not due to wild birds.Allthe HPAI outbreaks were A(H5N8) apart from three,which were reported as A(H5N2) from Bulgaria. Genetic analysis of the HPAI A(H5N8) viruses isolated from the eastern and central European countries indicates that this is a reassortant between HPAI A(H5N8) viruses from Africa and LPAI viruses from Eurasia. Two distict subtypes were identified in Bulgaria, a novel reassortant A(H5N2) and A(H5N8) that is persisting in the country since 2016. There could be several reasons why only very few HPAI cases were detected in wild birds in this 2019-2020 epidemic season and a better knowledge of wild bird movements and virus-host interaction (e.g. susceptibility of the hosts to this virus) could help to understand the reasons for poor detection of HPAI infected wild birds. In comparison with the last reporting period, a decreasing number of HPAI A(H5)-affected countries and outbreaks were reported from outside Europe. However, there is considerable uncertainty regarding the current epidemiological situation in many countries out of Europe. Four human cases due to A(H9N2) virus infection were reported during the reporting period from China.

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.