Virus World

H5N8 and H5N1 high pathogenicity avian influenza viruses (HPAIVs) caused outbreaks in poultry farms in Japan from November 2021 to May 2022. Hemagglutinin genes of these viruses belong to clade 2.3.4.4B and can be divided phylogenetically into the following groups: 20A, 20E, and 21E. In this study, we compared the infectivity and transmissibility of HPAIVs from three groups of chickens. Representative strains from 20A, 20E, and 21E groups are A/chicken/Akita/7C/2021(H5N8)(Akita7C), A/chicken/Kagoshima/21A6T/2021(H5N1)(Kagoshima6T), and A/chicken/Iwate/21A7T/2022(H5N1)(Iwate7T), respectively.

Fifty percent lethal dose of Akita7C in chickens (103.83 fifty percent egg infectious dose (EID50)) was up to seven times lower than those of Kagoshima6T and Iwate7T (104.50 and 104.68 EID50, respectively). Mean death times for Akita7C- and Kagoshima6T-infected chickens (3.45 and 3.30 days, respectively) were at least a day longer than that of Iwate7T (2.20 days). Viral titers of the trachea and cloaca of Iwate7T-infected chicken were the highest detected. The transmission rate of the Akita7C strain (100%) was markedly higher than those of the two strains (<50%). These data suggest that the infectivity and transmissibility of the Akita7C strain (H5N8) in chickens are higher than those of H5N1 viruses, providing fundamental information needed for formulating effective prevention and control strategies for HPAI outbreaks.

Published in Viruses (jan. 17, 2023):

https://doi.org/10.3390/v15020265 

Russia has registered the first case of a strain of bird flu virus named A(H5N8) being passed to humans from birds and has reported the matter to the World Health Organization (WHO), Anna Popova, head of consumer health watchdog Rospotrebnadzor, said on Saturday.  Outbreaks of the H5N8 strain have been reported in Russia, Europe, China, the Middle East and North Africa in recent months but so far only in poultry. Other strains - H5N1, H7N9 and H9N2 - have been known here) to spread to humans. Russia reported the case of human infection to the WHO “several days ago, just as we became absolutely certain of our results,” Popova said on Rossiya 24 state TV. There was no sign yet of transmission between humans, she added. Seven workers at a poultry plant in Russia’s south had been infected with the H5N8 strain in an outbreak at the plant in December, Popova said, adding that the individuals involved felt fine now. “This situation did not develop further,” she said.

In an email WHO’s European arm said it had been notified by Russia about a case of human infection with H5N8 and acknowledged this would if confirmed be the first time the strain had infected people. “Preliminary information indicates that the reported cases were workers exposed to bird flocks,” the email said. “They were asymptomatic and no onward human to human transmission was reported. “We are in discussion with national authorities to gather more information and assess the public health impact of this event,” the email added.  The majority of human bird flu infections have been associated with direct contact with infected live or dead poultry, though properly cooked food is considered to be safe. Bird flu outbreaks often prompt poultry plants to kill their birds to prevent the virus from spreading, and avoid importing countries having to impose trade restrictions. The vast majority of cases are spread by migrating wild birds, so producing countries tend to keep their poultry indoors or protected from contact with wildlife. Siberia’s Vector Institute said on Saturday it would start developing human tests and a vaccine against H5N8, RIA news agency reported.

The emergence and global spread of the highly pathogenic H5N8 avian influenza virus (AIV), a pathogen that has caused continuous and ongoing outbreaks with massive mortality in both wild and farmed birds across Eurasia and Africa throughout 2020, represents a considerable public health concern — particularly considering the first human cases of H5N8 infection were first reported last December. In a Perspective, Weifeng Shi and George Gao discuss the emergence and zoonotic potential of the H5 AIV lineages. Shi and Gao argue that vigilant surveillance and rigorous infection control measures for these emerging viruses are critical to avoid further human spillovers that could result in new and devastating pandemics.

Perhaps overshadowed by the ongoing global COVID-19 pandemic, over the past year, H5N8 infections in both wildfowl and poultry have been identified in at least 46 countries across Europe, Asia, and Africa. While these outbreaks have led to the death or slaughter of many millions of birds worldwide, they’ve also notably resulted in at least one spillover event in Russia, where seven poultry farm workers tested positive for H5N8 virus. According to the authors, the rapid global spread of this AIV and its demonstrated ability to cross the species barrier, transmitting to humans, makes it a major concern to not only farming and wildlife security, but also global public health. Shi and Gao suggest that the surveillance of highly pathogenic AIVs in poultry farms, live markets, and wild birds must become a global priority.

Cited publication available in Science (May 21, 2021):

https://doi.org/10.1126/science.abg6302