Australia reported its first human case of highly pathogenic H5N1 avian influenza today. The Victorian Department of Health reported that a young child in Victoria became sick with the virus after returning from a trip to India. While the child's illness was severe and required hospitalisation, they fortunately made a full recovery. The department advises there is no evidence of infection in the child's family members, and that the risk to the general public is considered very low due to the low transmissibility of this type of influenza. Despite the infection occurring back in March, the necessary testing to confirm the viral subtype was only completed last weekend, according to the Victorian chief health officer, Dr Clare Looker, who was interviewed on ABC Melbourne today.
Cases of bird flu in humans thankfully remain incredibly rare despite the global spread of H5N1 in birds and other animals, though infections can be very serious and the reported mortality rate can be up to 50%. Other human cases have included an infection in a Texas dairy farmer, whose clinical signs were limited to a mild conjunctivitis. There are currently more than 50 dairy herds affected by bird flu in the US. So far, no other human cases have been reported in that country, though some public health figures are concerned that additional human cases could be missed due to a lack of testing.
In an unwelcome coincidence, highly pathogenic avian influenza was reported on an egg farm in Meredith, Victoria, on the same day. While this is terrible news for the farm owners (and the hundreds of thousands of chickens that will need to be culled to eradicate the risk of the infection spreading), the viral subtype is reported as H7N3 rather than the H5N1 subtype that has devastated poultry and wildlife globally in recent years and was the cause of the Victorian child's infection. The H7 subtype is the usual influenza subtype seen in Australian poultry outbreaks, according to Dr Graeme Cooke, Victoria's chief veterinary officer, also speaking on ABC Melbourne this afternoon. This subtype circulates naturally in wild birds (typically waterbirds such as ducks) and sometimes causes disease outbreaks if it spreads to farmed poultry. Dr Cooke also noted that as the infection has only just been identified, the risk to surrounding poultry farms is still uncertain. Unlike H5N1, the H7 subtype does not usually infect animals besides birds.
Avian influenza remains a disease of enormous concern to Australian wildlife, agriculture and public health. While highly pathogenic H5N1 remains exotic to Australia, a future incursion in birds or wild aquatic mammals is considered likely. Public awareness will play a critical role in detecting the virus. You can report any unusual wild bird mortalities to the national Emergency Animal Disease hotline on 1800 675 888.
You can read more about the current global avian influenza panzootic in this dontlickthatduck feature article.
This post was edited to correct the influenza subtype from H7N7 (according to initial reports) to H7N3 (confirmed 23/5/24).
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