Global fears as bird flu spreads to cattle
The spread of H5N1 bird flu in a growing list of countries and species is “definitely cause for concern”, says a virologist carrying out sampling in New Zealand.
United Nations officials have described avian influenza virus, which has killed tens of millions of poultry since 2020, and spread to 23 countries, as a “significant public health concern”.
Scientists have been surprised at H5N1’s ability to jump to other species, with more than a dozen herds of dairy cows in the United States thought to have been infected via exposure to wild birds.
World Health Organisation chief scientist Dr Jeremy Farrar said the “great concern” was that the virus would develop the ability to infect humans — and ultimately spread between us.
So far, that hasn’t happened — but the case fatality rate among the several hundred people who have caught it, estimated at just over 50 per cent, is worryingly high.
Farrar cautioned vaccine development was not “where we need to be”, and not all the world’s public health agencies had capability to diagnose it.
New Zealand is yet to report a case, and officials have advised our dairy industry the country’s isolation has made the risk of wild birds bringing it here low.
The Ministry for Primary Industries had systems in place to prevent it arriving here through other pathways, and to detect any suspected cases early.
Otago University virologist Dr Jemma Geoghegan said while the risk to humans was still low at the present time, “there’s definitely cause for concern that there are so many different mammalian hosts getting infected”.
“There’s been a massive expansion on the host range of even mammalian spillovers, which is like nothing I have seen before.”
The more often that occurred, she said, the more opportunity the virus had to evolve.
“The rapidity of which [the spread of the virus] has happened is quite outstanding, so it’s definitely something we need to be better prepared for.”
Geoghegan and ESR scientist Dr David Winter have been collecting samples from places plentiful with sea, shore and water birds, including “flyway” sites where birds typically enter the country.
Meanwhile, a new study coauthored by Geoghegan has revealed New Zealand’s native long-tailed and lesser short-tailed bats harbour a surprising diversity of viruses, despite living in isolation for millions of years.
The study, which sampled bat droppings, also found both species had the same type of coronavirus — meaning the virus had jumped from one to the other in the recent past.
“While we know that viruses can jump to new hosts and cause disease outbreaks, it is usually between closely related hosts,” Geoghegan said. “Since New Zealand isn’t home to too many terrestrial mammals, particularly any that live in large population densities and near these bats’ habitats, the risk for spillover is low. Knowing about these viruses and monitoring their evolution and diversity, especially if any changes to the bat population occurs such as home range and habitat, can allow us to be better prepared for future disease outbreaks.”