The Bird Flu Virus That Has Infected People in Russia

(Bloomberg) — New strains of influenza are constantly emerging. Although the virus is associated with winter epidemics of respiratory disease in people, wild migratory birds are flu’s main target — and are responsible for much of its global distribution. An avian flu variant that’s been spreading in wild birds and occasionally spilling over and killing poultry for years recently caused the first reported human infections in southern Russia. Authorities have found no sign this particular virus is being transmitted from person to person. But new strains capable of infecting people raise concern because of the potential for them to mutate and become better suited to human respiratory tracts, potentially sparking dangerous epidemics.

Seven workers at a poultry plant in Astrakhan, near where the Volga River reaches the Caspian Sea, became mildly unwell after being infected with the H5N8 strain of bird flu in December, in an area where there had been an outbreak in poultry. The employees developed a sore throat, state media reported on Feb. 21. All are now in good health, after “the disease ended rather quickly,” Anna Popova, the country’s public-health chief, told reporters, adding that the virus spurred an immune response in those infected.

The more flu viruses spread, the more opportunity they have to mutate in ways that may increase their ability to infect people. Although the virus was found to transmit from birds to humans, there’s no evidence that it’s capable of spreading in the coughs and sneezes of infected people. “Time will tell how soon subsequent mutations will allow it to cross this barrier as well,” Popova said.

The poultry production facility where the infected people worked is reported to have been quarantined while poultry and associated products were destroyed, and the premises were disinfected. Scientists have started developing diagnostic tests and a vaccine as a precautionary measure. Virus particles collected from a nasal swab of a 28-year-old woman in Astrakhan have been genetically sequenced, and the information uploaded and shared on the GISAID database, an online portal used to track the evolution and geographic spread of influenza and, more recently, SARS-CoV-2 strains.

The first known H5N8 flu virus was detected in Ireland in 1983. It was found sporadically until 2014, when it emerged in South Korea and resulted in the culling of 600,000 fowl. In the following three years, it caused serious outbreaks on European and North American poultry farms most likely as a result of the intermingling of migrant ducks, swans and geese at their Arctic breeding grounds. The H5N8 strain is now reported in the Northern Hemisphere almost every year and is behind a fresh wave of outbreaks in Europe, Asia and Africa.

Influenza A viruses, the main culprit behind deadly pandemics, are classified into subtypes based on two surface proteins: hemagglutinin (or “HA” for short) and neuraminidase (or “NA”). The H5N8 virus has HA 5 protein and NA 8 protein. At least 16 hemagglutinins (H1 to H16), and 9 neuraminidases (N1 to N9) subtypes have been found in viruses from birds. Avian flu viruses have also been isolated, although less frequently, from mammalian species including rats, mice, weasels, ferrets, pigs, cats, tigers, dogs and horses as well as humans. The H1N1 and H3N2 subtypes are the main influenza A viruses circulating in people.