A New Bird Flu Jumps to Humans. So Far, It’s Not a Problem

When an avian flu virus hit a large poultry farm in Russia earlier this year, it was a reminder that the coronavirus that caused the pandemic wasn’t the only dangerous virus out there.

Authorities quickly tested the birds and put them into high gear, killing 800,000 chickens, disposing of the carcasses and cleaning up the farm to stop the potential spread to other chicken farms. But they were also concerned about people.

They tested the birds and sequenced the virus, finding it to be the H5N8 strain of avian flu, which was very dangerous to both wild and domestic birds. It is established in Asia and has caused increasingly fatal outbreaks in birds in Europe. H5N8 viruses have infected some poultry flocks in the United States, but the viruses come from a different, albeit related, virus line that differs from the current H5N8 viruses in Asia and Europe. Influenza viruses often combine and mutate in unpredictable ways.

In the short period from December 25, 2020 to January 14 of this year, more than seven million birds were lost to H5N8 outbreaks in Europe and Asia. In Europe alone there have been 135 outbreaks in poultry and 35 in wild birds. To put the numbers into context, humans consume around 65 billion chickens each year, and one estimate is that the number of chickens around the world is 23 billion at the same time.

As harmful as H5N8 was to birds, it never infected humans. Until February. Russian health authorities also tested about 200 of the people involved in cleaning up the Astrakhan farm for antibodies with nasal swabs and subsequent blood tests. They reported that H5N8 jumped to humans for the first time. Seven of the workers appeared to be infected with the virus, although none of them got sick. However, only one of these seven cases was confirmed by genetic sequencing of the virus.

However, the potential danger of the new virus and its leap to humans raised alarm bells for Dr. Daniel R. Lucey, a doctor and pandemic specialist at Georgetown University.

For Dr. Lucey did not seem to regard human infection with H5N8 as “of concern” to anyone else. He added, “I think it’s worrying.”

Updated

April 21, 2021 at 8:06 a.m. ET

Other scientists said they weren’t that concerned.

Dr. Florian Krammer, a flu researcher at the Icahn School of Medicine on Mt. Sinai, said he was more concerned about other avian flu viruses like H5N1, which have already been shown to be dangerous to humans. Another bird flu virus, H7N9, first infected humans in 2013. Since then, more than 1,500 cases have been confirmed and more than 600 people have been killed. There have only been three confirmed cases as of 2017 and the virus doesn’t jump from person to person easily.

It is always possible for any virus to develop human-to-human transmission and become more dangerous. But H5N8 would have to jump both hurdles. Compared to other viral threats, Dr. Krammer: “I’m not worried.”

Dr. Richard J. Webby, flu specialist at St. Jude Graduate School of Biomedical Sciences and director of the WHO Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, said all H5 viruses are cause for concern, some of them have infected humans and killed. But he said, “They all have the same kind of binding capacity to human cells, which is limited,” he said. Influenza viruses use a slightly different method of attaching to cells in birds than they do to cells in humans. Being good at one usually means not being good at the other.

Dr. Webby also said seven infections would certainly be of concern, but only one infection has been confirmed. The other six tests included nasal swabs and blood antibody tests. In people with no symptoms, he said, nasal swabs can simply indicate that they have inhaled virus. That wouldn’t mean it infected her.

Blood antibody tests could also be prone to error and may not be able to differentiate exposure to one flu virus from another.

He also saw no scientific basis that H5N8 was more likely than any other avian flu to develop human-to-human transmission. But any virus could develop this ability.

Dr. Lucey said he was encouraged to see that the U.S. Centers for Disease Control and Prevention had prepared a vaccine candidate for H5N8 before it infected people. Vaccine candidates are just a first step in planning potential problems and have not yet been tested. They exist for many viruses.

“Humans should be tested for the virus routinely, right at the time of the outbreak in birds,” said Dr. Lucey. He endorses the protocol used in Astrachahn, arguing that whenever there is a bird outbreak, health authorities should test people exposed to sick birds with nasopharyngeal swabs and an antibody test, followed by other antibody tests a few weeks later.

An upcoming editorial in Travel Medicine and Infectious Disease magazine also takes up the incident in Astrakahn and calls for increased surveillance of all H5 viruses.

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