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.

1. What happened?

Five women and two men aged 29 to 60 were infected with the H5N8 strain of bird flu while responding to an outbreak on an egg-producing farm in the administrative region of Astrakhan in December 2020. Some 101,000 of 900,000 hens died on the farm from Dec. 3-11, according to the World Health Organization. The affected workers developed no illness as a result of the infection, the WHO said on Feb. 26, contradicting a report by state media five days earlier that said the employees developed a sore throat. All are now in good health, after “the disease ended rather quickly,” Anna Popova, the country's public-health chief, told reporters on Feb. 20, adding that the virus spurred an immune response in those infected. All close contacts of the seven cases were monitored, and no one showed signs of clinical illness, the WHO said.

2. What's the risk?

Infections with similar bird flu viruses have been reported from China since 2014 in people with exposure to infected birds, according to the WHO, which considers the likelihood of human infections with H5N8 flu viruses to be “low.” “Based on currently available information, the risk of human-to-human transmission remains low,” the United Nations agency said.

3. What's the concern then?

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. Due to the constantly evolving nature of influenza viruses, WHO stresses global surveillance of flu viruses that may affect human or animal health. All human infections caused by a novel influenza subtype are notifiable under the International Health Regulations.

4. What are officials doing?

The egg 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.

5. What do we know about the strain?

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.

6. Why is it called H5N8?

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.

The Reference Shelf

• U.N. agencies and World Organization for Animal Health share information on animal influenza strains via their Offlu portal, including H5N8 in migratory birds.
• The Center for Infectious Disease Research and Policy tracks the latest flu news.
• The U.S. Centers for Disease Control and Prevention's latest guidance on influenza.
• The World Health Organization shares information on seasonal flu.
• A QuickTake explainer on influenza viruses and why they pose a pandemic threat, and the swine flu virus in China that has people worried.

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