Hundreds of thousands of birds at a country egg farm will be euthanised following an outbreak of bird flu, as a child is confirmed as Australia's first human case of a lethal strain spreading around the world.
The child, who returned to Victoria from India in March, experienced a "severe infection" after contracting the H5N1 strain but has made a full recovery, Victoria's chief health officer said.
"This is the first human case of H5N1 avian influenza in Australia," Clare Looker said.
"The avian influenza virus was detected through further testing of positive influenza samples that takes place to detect novel or concerning flu virus strains, as part of Victoria's enhanced surveillance system.
"Contact tracing has not identified any further cases of avian influenza connected to this case."
Dr Looker said the chance of more human cases was low because avian influenza does not spread easily between people.
Agricultural authorities have revealed a different strain of bird flu had been detected at an egg farm in regional Victoria.
Agriculture Victoria has ordered urgent testing after avian influenza was detected at a farm near Meredith, about 40km northwest of Geelong, following a number of poultry deaths.
Victoria's chief veterinary officer Graeme Cooke said the outbreak likely involved the H7N7 strain, different from the highly pathogenic H5N1 variant.
"There is a type of virus which is causing great concern in the USA and other parts of the world and has behaved unusually in that it has infected dairy cattle and some other marine mammals," Dr Cooke told the ABC's Country Hour.
"This is not the strain that we're dealing with. This is a strain that's occurred in Australia before. It's likely not new."
H7N7 was the most common strain of bird flu in Australia, Dr Cooke said.
One of the strains in the last bird flu outbreak in Australia in 2020, which affected one-in-three egg farms in Victoria, was a H7 strain.
Samples of the virus have been sent to the Australian Centre for Disease Preparedness in Geelong for further testing.
"Agriculture Victoria is responding with staff on the ground supporting the business with further laboratory investigations as necessary," Dr Cooke said.
The property has been placed into quarantine with a 5km radius and several hundred thousands of birds at that business will be "depopulated", he said.
"If this disease is allowed to spread, it would very much have an effect on the economic life of the poultry sector but there's also a lot of jobs in rural Victoria which are related to the industry," Dr Cooke said.
Australia's Chief Veterinary Officer Beth Cookson told AAP authorities are still considering the size of the quarantine area.
"The response will attempt to stamp out and eradicate the virus from the affected farm, so that will mean the destruction of the poultry on that premises," Dr Cookson said.
The outbreak has put farmers on high alert with extra biosecurity measures in place.
"For those within that area, we would encourage everyone to increase their level of biosecurity on their farms," Dr Cookson said.
Mary Wu from the Australian Chicken Meat Federation said while the disease appeared to be confined to a single egg farm, meat producers were on alert.
"We are very relieved that it's not the international strain, but we still take it extremely seriously and are acting very quickly," Dr Wu said.
Avian influenza is a highly contagious viral infection which can cause severe symptoms and sudden death in domestic poultry, wiping out entire populations.
Wild birds are the natural host for the disease and it can spread through close contact or contaminated environments.
Authorities have reassured the public that eggs and poultry products in supermarkets do not pose a risk and are safe to consume.
