When a bird flu virus hit a major poultry farm in Russia earlier this year, it reminded us that the coronavirus that caused the pandemic wasn’t the only dangerous virus.
Authorities quickly tested the birds and shifted into high gear, killing 800,000 chickens, discarding the carcasses, and cleaning the farm to stop the possible 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, very dangerous to both wild and domestic birds. It is located in Asia and is increasingly causing deadly outbreaks in birds in Europe. H5N8 viruses have infected some poultry flocks in the United States, but the viruses come from a different but related virus line, different from the current H5N8 viruses in Asia and Europe. Flu viruses often combine and mutate in unpredictable ways.
In the short period from December 25, 2020 to January 14 this year, more than seven million birds were lost to H5N8 outbreaks in Europe and Asia. In Europe alone, there were 135 outbreaks among poultry and 35 among wild birds. To put the numbers into context, humans consume about 65 billion chickens every year, and it is estimated that the number of chickens in the world is 23 billion at any given time.
As harmful as H5N8 is to birds, it has never infected humans. Until February. The Russian health authorities also tested about 200 of the people involved in the clean-up of the farm in Astrakhan, using nasal swabs and later blood tests for antibodies. They reported that H5N8 had jumped to humans for the first time. Seven of the workers were found to be infected with the virus, although none of them became ill. However, only one of those seven cases was confirmed by genetically sequencing the virus.
Nonetheless, the potential danger of the new virus and its leap to humans set alarm bells for Dr. Daniel R. Lucey, a physician and pandemic specialist at Georgetown University.
According to Dr. Lucey, no one else seemed to consider the infection of humans with H5N8 as “concerning”. He added, “I think it is concerning.”
Other scientists said they weren’t that concerned.
Dr. Florian Krammer, a flu researcher at the Icahn School of Medicine in Mt. Sinai, said he was more concerned about other avian flu viruses such as H5N1 that have already proven dangerous to humans. Another bird flu virus, H7N9, first infected humans in 2013. Since then, there have been more than 1,500 confirmed cases and more than 600 deaths. There have been only three confirmed cases since 2017, and the virus doesn’t jump from person to person easily.
It is always possible that any virus can develop human-to-human transmission and also become more dangerous. But H5N8 should overcome both hurdles. Compared to other viral threats, Dr. Krammer said, “I’m not worried.”
Dr. Richard J. Webby, an influenza specialist at the St. Jude Graduate School of Biomedical Sciences and director of the WHO’s Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, said all H5 viruses are of concern because some of them infected and killed people. But, he said, “They all have the same kind of binding capacity to human cells, which is limited,” he said. Flu viruses use a slightly different way of attaching to cells in birds than cells in humans, and being good at one usually means not being good at another.
Dr. Webby also said that while seven infections would certainly be of concern, only one infection has been confirmed. The tests of the other six include nasal swabs and blood antibody tests. In people without symptoms, he said, nasal swabs can simply indicate that they have inhaled a virus. That wouldn’t mean it had infected them.
Blood antibody tests also have a potential for error, he said, and may not be able to distinguish exposure to one flu virus from another.
Nor did he see any scientific basis to suggest that H5N8 is more likely than any other avian flu to develop human-to-human transmission. But any virus could develop that ability.
Dr. Lucey said he was encouraged to see that the U.S. Centers for Disease Control and Prevention had prepared a candidate vaccine for H5N8 before it infected humans. Candidate vaccines are just the first steps in planning for potential problems and have not yet been tested. They exist for many viruses.
“Humans should be routinely tested for the virus right at the time of the outbreak in birds,” said Dr. Lucey. He is in favor of the protocol followed in Astrakahn and states that for any outbreak in birds, public 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.
A forthcoming editorial in the journal Travel Medicine and Infectious Disease also addresses the Astrakahn incident, calling for increased monitoring of all H5 viruses.