Australia: Updates On Imported H5N1 Case & Two Outbreaks of H7N3 On Farms In Victoria

Victoria : Credit Wikipedia

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We've a bit more on yesterday's belated announcement (see Australia: Victoria Reports Imported H5N1 Case (ex India)) of Australia's first brush with H5N1, along with reports on two poultry farms being hit with HPAI H7N3.  

Via The Conversation we've an article by - By C Raina MacIntyre, Professor of Global Biosecurity, and PhD Candidate Haley Stone, both of UNSW Sydney - providing an excellent overview of both events published overnight in Bird flu is hitting Australian poultry farms, and the first human case has been reported in Victoria. Here’s what we know.

The entire report is worth reading in its entirety, but a few highlights include:

• The imported H5N1 Case is reportedly a 2-year-old girl
• While reportedly `very unwell', she is now fully recovered
• There is no word on where in India the girl returned from, or of any possible exposure risks
• GISAID data shows the was infected with an older H5N1 clade 2.3.2.1a virus, which is known to circulate in poultry in Bangladesh and India
• This clade is different from the clade (2.3.4.4b) affecting the United States, and most of the world, and distinct from the clade 2.3.2.1C  which has caused a dozen cases in Cambodia  over the past 15 months.

There are still a number of gaps in our knowledge, including when this case was finally diagnosed, and why it has taken this long for us to learn about it.

The other avian influenza story out of Australia was the announcement yesterday that a large poultry farm - also in Victoria - had been struck by HPAI H7N3.  

While the Australian continent has never seen H5N1 in wild birds or in poultry, H7 outbreaks have been recorded a number of times since the 1970s.

Yesterday's outbreak in Meredith was confirmed in the following statement from Agriculture Victoria:

Movement controls in place for avian influenza

23 May 2024

Agriculture Victoria has confirmed that the H7N3 high pathogenic strain of avian influenza virus is the cause of a number of poultry deaths at an egg farm near Meredith.

Movement controls are now in place to prevent any spread of the virus while the property is quarantined, all poultry are safely disposed of, and the site is cleared of the infection. Contact tracing is also underway to determine the source and spread of the infection.

This includes a Restricted Area covering a five-kilometre radius around the infected premises and a broader Control Area buffer zone covering an area of 20 kilometres.

This restricts the movement of poultry, poultry products, equipment and vehicles on or off properties in these areas. Penalties apply for those who do not follow these restrictions.

Victoria’s Chief Veterinarian Graeme Cooke said Agriculture Victoria staff are on-the-ground to support the business and working closely with industry to contain and eradicate the virus.

(Continue . . . )

Although the press releases don't specify how large this farm is, the Australian Broadcasting System is reporting `hundreds of thousands' of birds have been culled. 

Despite the quarantine measures mentioned above, a second farm - some 70 miles away in Terang - is now reported to have been infected with H7N3 as well.  Both farms are said to be `linked', although exactly how is not stated.

Although human H7 infections (LPAI & HPAI) had long been regarded as less serious than H5 - the 5 year reign of H7N9 in China (2013-2018) showed what an H7 virus was capable of; infecting more than 1,500 people and killing roughly 40% of them.

H7N9 Epidemic Waves - June 14th 2017 - Credit FAO

In addition to H7N9, we've seen a number of H7 spillovers around the world, including;

• In 2018 a woman in Jiangsu Province, China was seriously infected by an H7N4 virus (see WHO Update & Risk Assessment On Avian H7N4), spending 21 days in the hospital
• NYC's 2016 dramatic H7N2 outbreak in cats, and spillover into animal shelter workers (see J Infect Dis: Serological Evidence Of H7N2 Infection Among Animal Shelter Workers, NYC 2016)
• 3 mild cases of LPAI H7N7 in Italy in 2013 (see ECDC Update & Assessment: Human Infection By Avian H7N7 In Italy).
• In 2006 1 person in the UK was confirmed to have contracted H7N3, and the following year, 4 people tested positive for H7N2 – both following local outbreaks in poultry.
• The Fraser Valley H7N3 outbreak of 2004 resulted in at least two human infections, as reported in this EID Journal report: Human Illness from Avian Influenza H7N3, British Columbia.
• And in 2003 a large outbreak of H7N7 (89 confirmed, 1 fatality) in the Netherlands – with nearly all reported cases having very mild (often just conjunctivitis) symptoms.

Not so very long ago, avian influenza was primarily a seasonal concern.  We'd start seeing reports in October or November, and they would peak over the winter, and pretty much end by April or May.  

That dynamic has changed over the past few years, with HPAI H5 now firmly entrenched in the southern hemisphere, and with the virus showing greater persistence in wild birds and mammals  over the summer.

While avian flu remains highly unpredictable, a summer respite seems unlikely. 

Stay tuned.