Dr. Richard Webby, The director of the World Health Organization Collaborating Center for the Study of Influenza Ecology in Animals and Avians and the Director of the Host-Microbial Interactions Department of Virology at St. Jude Children’s Research Hospital predicts a milder H5N1 (avian) influenza season.
“I think it’s clear now that the H5 virus is settling more into a seasonal pattern, where we’re seeing increased activity as migratory birds fly south and increased spillover from poultry to wild mammals,” Webby said. “This time last year we saw the emergence of a very suitable virus that spread very widely and infected many birds. That’s essentially what the prediction was based on.”
And he said wild birds, the main vectors, are likely immune.
Learn more about the migration patterns of these animals:
“We’ve seen a lot of activity in the last year, so it’s likely that a lot of wild birds have been exposed to this virus. Certainly adult birds and those that haven’t succumbed to the infection build up an immunity to it,” Webby said. “So theoretically, there should be quite a bit of immunity to the H5 virus in the population this season. We’re certainly seeing infections in poultry and wild species as the season starts, but there’s the idea that population immunity is a little bit higher in wild bird populations, which means there may be a little bit less virus circulating.”
Avian influenza surveillance
Virus surveillance remains key, and Webby’s institution, St. St. Jude has a long-standing partnership with the World Health Organization (WHO) and says it has the tools and strategies to remain vigilant in monitoring the spread and severity of potential outbreaks.
“St Jude Children’s Research Hospital is a World Health Organization Collaborating Center within the Global Influenza Programme, which has been given this designation since 1975. There is a network of laboratories within the Global Influenza Programme. They are just the Risk or Global Influenza Surveillance and Response System. There are currently more than 130 odd laboratories around the world that collect information, primarily during the seasonal flu season, and that information is used to recommend seasonal flu shots. But there is also a lot of work within these discussions. H5 “We need a lot of information and data sharing about animal strains, including these.”
Webby also says he utilizes the WHO’s Tool for Influenza Pandemic Risk Assessment (TIPRA).
“This mirrors a similar tool the U.S. CDC has that essentially assesses the relative risk of many emerging flu strains, including H5N1,” he said. So this tool contains a lot of very basic research information about these viruses. What diseases do viruses cause? Is there mass herd immunity in humans? How widespread is it in animal populations? “All of this information flows into this tool, and at the other end it produces a relative ranking of all these threats, ranking them according to their likelihood of presenting themselves to humans and the expected impact if they appear to humans.”
Webby also said they are monitoring what types of mammals are infected with the virus and what rates of transmission to humans are occurring.
“If we start to see transmission in other mammalian hosts, we would have some concerns. Likewise, if we see an increase in human cases, that would certainly be very direct evidence that something may be changing. From a more virological perspective, we are also monitoring H5 viruses that are spreading not only in the United States or the Americas, but also in other parts of the world.
We know some of the molecular signatures. This means that when these viruses are sequenced, there are certain changes in the virus that are likely to increase the threat or potential risk to humans. One thing is very clear, and that is how the influenza virus interacts with host receptors. Influenza viruses also bind to host receptors that are sugars, but they bind to one form of that sugar. “Human-adapted viruses bind to the same sugars, but they bind those sugars in a slightly different way, and we know the markers on the virus that regulate that switch, so that’s one of the things we’re looking for.”
Not only is the possibility of a mild season good news, but the way the virus behaves in general is also encouraging, Webby says.
“While the H5 virus is circulating in birds, there does not seem to be much pressure for the virus to change to become more infectious to humans,” Webby said.
