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New Delhi, February 27, 2021 :
Between 3 and 11 December, a total of 101 000 of 900 000 egg laying hens on the farm died. This high mortality rate prompted an investigation. Samples were collected from these birds and an initial detection of avian influenza A(H5N8) was performed by the Russian regional veterinary laboratory. On 11 December, the outbreak was confirmed by the World Organisation for Animal Health (OIE) Reference laboratory, and the Federal Centre for Animal Health (FGBI-ARRIAH), in Vladimir, the Russian Federation. Outbreak containment operations started immediately and continued for several days due to the large size of the poultry farm.
The cases remained asymptomatic for the whole follow up duration (several weeks). Follow-up nasopharyngeal swabs were collected during medical observation period and were tested negative for avian influenza A(H5N8). No obvious clinical manifestations were reported from any farm workers under medical surveillance, their family members, or other close contacts of the seven cases. Additionally, acute and convalescent sera was collected from the seven positive human cases for serological testing. The results were suggestive of recent infection.
Influenza A(H5N8) viruses isolated from this poultry outbreak in Astrakhan belonged to clade 2.3.4.4b of avian influenza A(H5Nx) viruses. In 2020, avian influenza A (H5N8) viruses were also detected in poultry or wild birds in Bulgaria, the Czech Republic, Egypt, Germany, Hungary, Iraq, Japan, Kazakhstan, the Netherlands, Poland, Romania, the United Kingdom, and the Russian Federation.
Public health response :
On receiving the initial signal of a probable outbreak of highly pathogenic avian influenza (HPAI) at the poultry farm on 3 December 2020, the national authorities took immediate measures including cessation of poultry production cycles, and product transportation from the affected farm.
Between 11 and 18 December, several measures including culling and disposing of poultry, eggs, litter and disinfection of contaminated premises were taken as part of outbreak response activities
During and after the culling of all the poultry, nasopharyngeal swabs and serum samples were collected from poultry farm workers and personnel involved in outbreak response at the farm. The surveillance activities, both within and outside of the containment area, was intensified. A total of 24 close contacts of the confirmed cases have been identified and traced. In total, 150 individuals were monitored for clinical indication of respiratory disease and received antiviral prophylaxis therapy. No symptoms were reported among these individuals.
Whole Genome Sequencing of avian influenza A (H5N8) viruses isolated from poultry and from one of the seven human cases was performed and were uploaded to the Global Initiative on Sharing All Influenza Data (GISAID) database on 20 February 2021. Genetic and phenotypic characterization of the virus is ongoing.
WHO is following up with the public health authorities in the Russian Federation, including implementation of public health measures warranted by such events, and with the WHO Global Influenza Surveillance and Response System (GISRS) on further analysis and assessment of the virus materials and serum samples. On 20 February, a special briefing by the head of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing was organized for the state Russian media to inform the public about these cases and the implications.
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