All poultry and captive birds in England will legally be required to be kept indoors as part of measures to tackle the country's largest-ever outbreak of avian flu.
The British government said on Monday the mandatory measures would be introduced from midnight on November 7.
This is the largest-ever outbreak of avian flu in the UK, with 200 confirmed cases in the past 12 months.
The mandatory housing order will extend measures already in force in parts of eastern England to the whole nation, following an increase in the risk of bird flu in wild birds to "very high", the government said in a statement.
Bird keepers will be required to follow stringent biosecurity measures including disinfecting clothing, footwear, equipment and vehicles and keeping mortality records.
"We are now facing this year, the largest ever outbreak of bird flu and are seeing rapid escalation in the number of cases on commercial farms and in backyard birds across England," UK Chief Veterinary Officer Christine Middlemiss said.
"The risk of kept birds being exposed to disease has reached a point where it is now necessary for all birds to be housed until further notice."
In the same statement, the UK Health Security Agency said it continued to advise that the risk to public health from the virus was very low.
What is bird flu?
Bird flu is caused by a handful of influenza viruses, just like the seasonal flu that circulates each winter.
But while seasonal flu infections rise in cool weather and spread easily in human populations, bird flu is transmitted only between animals or from animals to humans.
Larger birds, such as ducks and geese, tend to ferry bird flu viruses around the world, said Frank Wong, a CSIRO Australian Animal Health Laboratory microbiologist and World Organisation for Animal Health reference expert for highly pathogenic and low pathogenic avian influenza.
However, if smaller migratory birds such as shorebirds are infected with bird flu, they're more likely to delay their migration, or not set out on their journey at all.
"When the birds congregate [to feed and breed] … mixing of birds also results in mixing of viruses, including influenza viruses. Then when the birds fly south or westwards for the winter, they carry those viruses with them," Dr Wong said.
"If those wild birds interact with domestic birds, the viruses they're carrying might spill over and cause outbreaks in domestic poultry."
What's the bird flu situation in Australia?
Australia is in a pretty safe place when it comes to bird flu.
There have been only eight outbreaks of the disease in Australia since the 1970s, with the biggest happening in Victoria last year.
Unlike Europe and Asia, Australia has no large waterfowl seasonal migrations from abroad, which bring in new viruses each year, Dr Wong said.
Australia also has stringent controls around how poultry is shuttled into and around the country.
Among other biosecurity measures, local regulations state that poultry farms cannot be located near lakes or other bodies of water.
"In Australia, we don't want these viruses around, so regardless of if it's a low-pathogenic strain or a high-pathogenic strain, depopulation is the way to go," said Ricardo Soares Magalhães, associate professor in population health and biosecurity at the UQ School of Veterinary Science.
What is depopulation and how does it work?
Depopulation — or culling — may seem an extreme measure, but the disease can quickly cause debilitation and death, especially if it's a highly pathogenic strain.
"The best strategy from an animal welfare perspective is to depopulate the flock," Dr Soares Magalhães said.
"That happens on a radius of 3 kilometres around the affected zone, and then we impose a surveillance zone out to another 7km."
How do humans get bird flu?
For a human to get bird flu, they need direct contact with infected birds, or contaminated feathers or faeces.
It can't be passed on by eating eggs or cooked meat.
So far, there's been very little human-to-human bird flu transmission, but that doesn't mean new strains won't gain that ability, Dr Soares Magalhães said.
"COVID [which probably originated in bats] is a good example of that."
Pigs can be infected with more than one flu virus, and if that happens, they can act as a virus mixing vessel of sorts to produce new viruses.
ABC/Reuters
