Australia: SA Reports 1st H5N1 Detection in a Marine Mammal (long-nosed fur seal)

 

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Less than a year ago HPAI H5N1 was detected on Heard Island - an Australian external possession 4000 km south west of Perth - resulting in the the deaths of thousands of marine mammals and seabirds (see Preprint: Mass mortality of southern elephant seals during multi-species outbreak of HPAI H5N1 on sub-Antarctic Heard Island).

Drone surveys revealed mass mortality in southern elephant seals, with 8,573 pups (62%) recorded dead across Heard Island by the final surveys. Mortality increased at an average rate of 5.6% per day in a subset of harems, and the highest observed mortality in a harem was 97%. Based on the average (76%) mortality in the final surveys, total estimated pup mortality at Heard Island was 13,359 (from a total population of 17,364 pups), though this may be an underestimate as mortality was ongoing at this time. 

Just over 2 months ago HPAI H5N1 arrived - via migratory birds - to the Australian mainland. Since then we've been watching as thousands of birds - both migratory and local - have succumbed to the virus.  

While all previous detections have been limited to birds, overnight Australia confirmed HPAI finding in a first mammalian casualty in the following brief announcement. 

23 August 2026

Attributable to Australian Chief Veterinary Officer, Dr Beth Cookson:

Testing at CSIRO’s Australian Centre for Disease Preparedness (ACDP) has confirmed H5 high pathogenicity avian influenza (bird flu) in a long-nosed fur seal, found at Beachport in South Australia. This is the first detection of H5 bird flu in a mammal species in Australia.

Although this is a concerning development, it is not unexpected that H5 bird flu has been detected in other wildlife, particularly marine mammals, in areas where there are high levels of infection in wild birds.

From 12 August 2026, we have changed how we report on H5 bird flu detections. Reporting will be based on events, rather than individual detections. See birdflu.gov.au for the latest information.

There remain no detections in poultry or in our agricultural production system.

The risk to human health remains low.

We get a few more details from the SA August 23rd update, which reads in part:

The long-nosed fur seal was found dead with no signs of injury and reported to the EAD hotline by a member of the public on Wednesday, 19 August. It was not reported as a suspect detection initially as state-based testing was inconclusive. However, samples were dispatched to ACDP for urgent testing which confirmed the H5 bird flu detection.

Based on the HPAI carnage we've seen among marine mammals elsewhere in the world (see UC Davis: High pathogenicity Avian Influenza in Pinniped conservation), today's announcement likely only heralds a much larger impact. 

And while the Australian government still reminds the public that poultry and agricultural livestock remain unaffected, how long that happy status quo will stand is anyone's guess. 

That Touch of Mink Flu (H5N1 in Utah Edition)

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Mink are members of the Mustelidae family of carnivorous mammals, which also includes otters, badgers, weasel, martens, ferrets, and wolverines. Many of these species are susceptible to flu viruses – most notably ferrets – which are often used in influenza research.

Over the past 20 years we've looked a a number of concerning spillovers, including:

• 2009's That Touch Of Mink Flu, where at least 11 mink farms in the Holstebro municipality of Denmark were reported to be infected with a variant of the human H3N2 virus.

• In 2007, an antigenically distinct H3N2 Swine Influenza was detected in Canadian Mink, reported in a 2009 Journal of Clinical Microbiology study called Characterization of a Canadian Mink H3N2 Influenza A Virus Isolate Genetically Related to Triple Reassortant Swine Influenza Virus.

• A year earlier CIDRAP reported on a European mink found infected with an aggressive form of the H5 flu virus in the Blekinge region of southern Sweden near where H5N1 had been detected in wild birds.

• And even as far back as 1984, a large outbreak in Swedish mink farms was found to be due to the H10N4 avian virus.

We've seen literally dozens of reports of spillovers into mink since, including the generation of mink-variant COVID strains which - at least temporarily - circulated in humans in Europe back in 2020 (see Preprint: Emergence & Spread of SARS-CoV-2 Variants from Farmed Mink to Humans and Back - Denmark, June-November 2020).  

New alarms were raised in the fall of 2022 when H5N1 began spreading rapidly through a large mink farm in Spain (see Eurosurveillance: HPAI A(H5N1) Virus Infection in Farmed Minks, Spain, October 2022).

This mink-derived H5N1 virus from Spain carried a rare mutation (PB-T271A), which is believed to `enhance the polymerase activity of influenza A viruses in mammalian host cells and mice'. In 2023 the CDC issued an IRAT Risk Assessment On Mink Variant of Avian H5N1, finding it's scores had risen in 6 of the 10 parameters used to evaluate their zoonotic potential.

In 2023 we saw scores of fur farms (both mink & fox) in Finland hit by HPAI, resulting in massive culls.      

During that protracted outbreak, in PNAS: Mink Farming Poses Risks for Future Viral Pandemics, we looked at an opinion piece by Professor Wendy Barclay & Tom Peacock on why fur farms - and mink farms in particular - are high risk venues for both flu and SARS.

Spillovers into farmed animals are particularly worrisome, because they allow for serial transmission across a large number of hosts, which may result in host adaptation.

Since then, new studies have continued to emerge highlighting the risks, including:

• January 2025's Zoonosis & Public Health: Detection of a Reassortant Swine- and Human-Origin H3N2 Influenza A Virus in Farmed Mink in British Columbia, Canada.

• Last December's Viruses: Replication and Transmission of Influenza A Virus in Farmed Mink

Yesterday the USDA updated their Detections of Highly Pathogenic Avian Influenza in Mammals dashboard to include 6 captive American Mink in Utah infected with EA H5N1 (see below).

1 To protect data confidentiality, the county and mapped locations of these detections represent the approximate location of the State capitol.

Details are extraordinarily scant (even the county location is `masked'), but the dates of collection and confirmation all are quite recent (8/7 & 8/17).  This is presumably a fur farm, but no details are provided. 

I've found no media reports on this event, and there appears to be nothing publicly available on the Utah Agriculture Department Website. As of this writing, I don't find anything on the WOAH WAHIS website, either. 

Whether these mink were sick, or died, or how many others might be infected on the premises or at risk, and what steps are being taken to contain this outbreak, or protect farm workers, isn't stated. 

Utah has already been having a rough H5N1 summer, with 16 cattle herds reportedly infected since June, and nearly 1.5 million chickens culled due to the virus. 

There are disappointingly far too few details provided to make any reasonable assumptions about the size, or potential impact, of this outbreak.  Hopefully we'll get more details sooner rather than later. 

Note: After I posted this blog I noticed Hogvet51 has posted his own thoughts. If you aren't reading his substack, you should add it to your list.

CDC FluView Week 32: Two H1N2v Human Infections Reported in Michigan

 

Credit Wikipedia

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Nine days ago, in  Kent County MI Health Department Bulletin on Swine Flu (in pigs) at Local Fair, we learned of the death (and several illnesses) of pigs at a local county fair due to swine flu, and a health alert issued for possible human cases. 

Two days later, on Aug. 15th, we learned of one confirmed human infection with H1N2v from the Michigan Department of Health and Human Services (see Michigan DOH Confirms H1N2v (swine flu) in Fair Exhibitor).

While there were rumors of more than one `flu-like illness' among attendees to the county fair, until now we've heard of no other cases.  Today, the CDC announced a total of two confirmed H1N1v swine flu infections linked to this county fair. 

Novel Influenza A Virus Infections

Two human infections with influenza A(H1N2) variant (A(H1N2)v) virus were reported by the Michigan Department of Health and Human Services.

The patients, who are <18 years of age, initially developed illness and sought healthcare during the week ending August 15, 2026 (Week 32). The patients were not hospitalized, one patient received influenza antiviral treatment, and both are recovering from their illnesses.

Investigation by local and state public health officials identified that both patients, who have not had contact with one another, had attended the same agricultural fair where ill swine were present prior to their illness onset. No additional cases of human infection with A(H1N2)v virus associated with these cases or the fair have been identified.

These are the third and fourth human infections with a variant influenza virus reported in the 2025-2026 season; all four have been influenza A(H1N2)v viruses.

When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant” influenza virus. Most human infections with variant influenza viruses occur following exposure to swine, but human-to-human transmission can occur. It is important to note that in most cases, variant influenza viruses have not shown the ability to spread easily and sustainably from person to person.

No additional notification to WHO of this case is required per International Health Regulations (IHR). More information regarding IHR can be found at http://www.who.int/topics/international_health_regulations/en/.

Although it is possible there were other infections linked to this fair, most people who experience minor or even moderate flu-like symptoms never see a doctor, or are tested, for novel flu viruses. 

The CDC regularly advises people who are at higher risk of serious flu complications (including children under 5, adults over 65, pregnant women, and those with certain chronic medical conditions), to avoid pigs and the swine barn altogether.

Although the pandemic risk from swine variant viruses is currently regarded as low, the H1N1 pandemic of 2009 demonstrated just how quickly the status quo can change. 

Nature Comms: Trimester-dependent vertical transmission of H5N1 influenza virus through placental and mammary routes impairs offspring development

Photo Credit – CDC

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In late 2024, in EID Journal: Systematic Review of Avian Influenza Virus Infection and Outcomes during Pregnancy - among 30 pregnant women diagnosed with avian flu (H5N1 n = 16, H7N9 n = 13, and H5N6 n = 1) - researchers reported high mortality rates for both mothers (90.0%, 27/30) and their babies (86.7%, 26/30).

As we've discussed often (see Pregnancy & Flu: A Bad Combination), novel flu often exacts a heavy toll on expectant mothers and their unborn children.

Even during the relatively mild H1N1 pandemic of 2009, we saw studies (see BMJ: Perinatal Outcomes After Maternal 2009/H1N1 Infection) where pregnant women who were admitted to the hospital with an H1N1 infection experienced a 3 to 4 times higher rate of preterm birth, 4 to 5 times greater risk of stillbirth, and a 4 to 6 times higher rate of neonatal death.

We also know that during the 1918 pandemic an abnormally high number of pregnant women died from the influenza, and those that survived endured a very high miscarriage rate. Again, during the much milder 1957 Asian Flu, pregnant women reportedly suffered disproportionately higher mortality rates than non-pregnant women of the same age.

Historical reviews of both events are available in a Perspective, written by 3 CDC physicians (Sonja A. Rasmussen, Denise J. Jamieson, Joseph S. Bresee) and published in the CDC Journal of EID article, Pandemic Influenza and Pregnant Women in February of 2008.

As bad as they were, most of these effects have been attributed to the mother's immune response (fever, cytokine production, etc.) to the infection; not the vertical transmission of the virus to the fetus in utero.

A 2012 CDC study, however (Effects of influenza on pregnant women and infants) does cite H5N1 as potentially being an exception, due to its ability to cause extrapulmonary infection & viremia. Their conclusion, however:

"Therefore, the limited evidence to date suggests that vertical transmission of influenza viruses can occur but is likely to be very rare."

Last November we looked at a preprint (see Vertical Transmission of Bovine H5N1 Influenza Virus during Pregnancy and Lactation in Mice) which demonstrated that in (lab inoculated) pregnant mice (2nd Trimester), the bovine B3.13 H5N1 virus crossed the placenta (in a subset of litters) and, in a separate late-gestation experiment, spread through milk, infecting pups.

Exposed offspring were typically smaller, reached developmental milestones later, and showed lasting behavioral changes into adolescence.

Interestingly, they used two different isolates (A/bovine/Texas/98638/2024 and A/bovine/Ohio/B24OSU-439/2024), which produced different clinical courses and pathology in mice. 

The Texas isolate produced a faster, more lethal course and higher viral burdens in several tissues—including mammary, ovarian, and CNS tissues—than the Ohio isolate in mice. The authors elected to use the slower-progressing Ohio virus for their pregnancy experiments.

That (revised and renamed) preprint has now been published in Nature Comms, and is offered early (subject to additional edits) at the link below.  The full study is  lengthy, and at times, highly technical. 

Those wanting a deeper dive should download the PDF. I'll have a postscript after the break.

Trimester-dependent vertical transmission of H5N1 influenza virus through placental and mammary routes impairs offspring development

Brittany A. Seibert, Maclaine A. Parish, Sattya N. Talukdar, Tianle Zhang,

Jennifer A. Liu, Sabal Chaulagain, Jaiprasath Sachithanandham, Oscar Hernandez,

Cosette Schneider, Lynda Coughlan, Andrew S. Bowman, Richard J. Webby,

Jack R. Harkema, Andrew Pekosz & Sabra L. Klein

Nature Communications (2026) Cite this article 

We’re sharing this article early to provide faster access to peer-reviewed, accepted research. It is citable and carries a permanent DOI. This version is subject to further edits and will be replaced automatically by the final Version of Record. All legal disclaimers apply.

Abstract

Avian influenza H5N1 has pandemic potential and historically causes more severe disease in pregnant women than the general population. With increasing transmission of H5N1 detected among placental mammals, animal models are necessary for testing countermeasures, including during pregnancy. Pregnant outbred mice infected with a contemporary strain of bovine H5N1 during the second trimester equivalent causes in utero transmission, with infectious virus detected in the uterus, placenta, and fetus. Birth following third trimester infection results in offspring with decreased size, neurodevelopmental delays, and adolescent behavioral impairments, with infectious virus detected in the neonatal milk ring and lungs, as well as mammary tissues. H5N1 viral protein colocalizes with trophoblast cells in the placenta and epithelial cells in mammary tissue that spatially overlap with lectins for α2,3-linked SA. With the pandemic potential of H5N1, our vertical transmission model in placental mammals is essential for understanding viral spread and evaluating treatments during pregnancy.

       (Continue . . . )

The usual caveats apply; including a) mice have anatomical and immunological differences from humans. b) this study only looked at genotype B3.13, and c) and it is unknown how much these findings will actually translate to humans.

But even without vertical transmission, pregnant women and their offspring are presumed at higher risk during any flu outbreak.

Last February, in Viruses: Avian Influenza H5N1 Infection During Pregnancy: Preparing for the Next Flu Pandemic and Improving Perinatal Outcomes, we looked at a review article published in Viruses that looked at the limited data we have on novel flu and pregnancy, and argued that H5N1 could be particularly dangerous to pregnant women and their offspring if it should begin to spread in humans.

The authors proposed a basic algorithm for initial clinical management of suspected H5N1 in pregnancy and lobbied for prioritizing both antivirals and vaccines (when available) for high-risk patients, including those who may be pregnant.

While an H5Nx pandemic is by no means assured, pandemic history has not been kind to pregnant women and their offspring, making it imperative that we consider the risks - and how we might handle them - now, while we still have the luxury of time.

New Zealand Reports 3rd H5N1 Detection in a Wild Bird

Credit Wikipedia

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It has been just over a month since New Zealand reported their second H5N1 detection in a local bird (a swamp harrier hawk) found in the sparsely populated Wairarapa region on the north island (see map above).

Today, New Zealand has confirmed a 3rd detection - this time in a northern giant petrel, found dead on a remote Cape Palliser beach (also in the Wairarapa).

While it is likely there are other, as-yet undetected cases in New Zealand, they don't appear to have seen the same level of influx that Australia has had to deal with.   How long that will last is anyone's guess.

First the NZ announcement, then a brief update on Australia's numbers. 

Situation update: 21 August 2026

New Zealand has 3 confirmed detections of H5 high pathogenicity avian influenza (H5 bird flu).

New Zealand’s third case of H5 bird flu was confirmed on 21 August in a northern giant petrel, found dead on a remote Cape Palliser beach in the Wairarapa.

There is no evidence of any mass mortality in wildlife. There has been no detection in poultry.

Chicken and eggs remain safe to eat and bird flu is a very low risk to human health.

New Zealand is well prepared to respond to H5 bird flu and is working to protect poultry production and reduce impacts on wildlife and communities. Response and surveillance work has intensified in close coordination with industry partners and other agencies.

The Department of Conservation is implementing a vaccination programme for 300 core breeding birds from 5 of our most endangered birds – kākāpō, takahē, tūturuatu/shore plover, kakī/black stilt, and kākāriki karaka/orange-fronted parakeet.

Be alert and use good habits to limit the impact of bird flu

Keep your distance. Stay away from sick or dead wildlife. Keep pets away too.

Keep clean. Wash your hands and clean your gear after being outdoors.

Know when to report. If you see 3 or more sick or dead wild birds in a group, report it immediately to the exotic pest and disease hotline on 0800 80 99 66 or online at report.mpi.govt.nz

If you report online, select the ‘dead or dying wild birds’ option from the dropdown list and then the type of bird you have found. Don’t handle or move the birds.

Meanwhile, in Australia, the flow of information continues to be a bit confusing.

Depending on which DAFF (Department of Agriculture) page you land on (here or here), the last updated national bird flu numbers (as of this writing) are listed as being either 27 or  51 hours old (see double screenshot below).

The last avian flu update from Australia's Chief Veterinary Officer was on August 14th, and - while reporting formats are not uniform across the individual states - a quick perusal suggests that the national tallies are lagging a day or two behind local reporting. 

With the number of hotline reports of dead or sick birds now approaching 25,000 - far exceeding their ability to investigate and test - these sorts of delays are not unexpected. 

The DAFF bird flu site offers the following caveats:

Data disclaimer

Data reflects information provided by state and territory governments to the Australian Government as at 17:00 AEST daily. The Australian Government publishes this information for national reporting purposes. Responsibility for the accuracy, completeness and currency of the data remains with the relevant state or territory government. Due to differences in reporting timing, information on the national dashboard may differ from information published on state or territory government websites.

Approach to reporting

From 12 August 2026, we have changed how we report on H5 bird flu detections.

Reporting is now based on events, rather than individual bird detections.

An event may involve one or more birds. The new number of positive events captures all previously reported individual confirmed detections.

Definitions

Investigation: An event where one or more wild birds or wild mammals showing signs of H5 bird flu have been reported to state or territory authorities and samples have been collected for laboratory testing.

Positive event: An investigation where H5 bird flu has been confirmed through laboratory testing.

Hotline report: A report to relevant state or territory authorities through the Emergency Animal Disease Hotline or other official sources.

While continued surveillance is important to track the geographic spread - and increasing host-range - of H5N1 in Australia, the numbers posted each day become less significant over time.  

A reminder of how quickly an unprecedented event - like the first arrival of HPAI H5 to Oceania 2 months ago - can become the `new normal'.

Louisiana DOH Reports Naegleria fowleri infection in Louisiana resident

 Credit CDC

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Nearly every year we see a handful of rare - mostly fatal - brain infections caused by free living amoebas (Naegleria fowleri) that inhabit warm, fresh water (see A Reminder About Naegleria Season - 2019).

Dubbed the `brain eating amoeba' by the press - this infection is called PAM (Primary amebic meningoencephalitis) - and occurs when the amoeba enters the brain through the nasal passages, usually due to the forceful aspiration of contaminated water into the nose.

Not every PAM case is due to Naegleria, as Balamuthia mandrillaris and Acanthamoeba - and other non-Naegleria amoebic infections - can cause similar pathologies.

Last year the CDC's MMWR carried a report on a fatal 2024 case from Texas, which involved a previously healthy 71-year old woman who used unsterilized water to perform nasal irrigation.  

This is a common way that people around the world have become infected (see 2011's Neti Pots & Naegleria Fowleri).  The CDC and state health departments have long warned on the dangers of using tap water to perform nasal irrigation, and offer advice on safer alternatives. 

But most U.S. cases occur while swimming, often in warm stagnant freshwater lakes, rivers, canals, and ponds.  Less commonly, we've  seen infections attributed to water parks, private swimming pools, and even the public water supply. 

• In 2013, in Louisiana: St. Bernard Parish Water Supply Tests Positive For Naegleria Fowleri, we saw the tragic story of a 4-year-old Mississippi child visiting a St. Bernard Parish home, who (according to this NOLA.COM report) appears to have contracted the amoeba while playing with a water hose and a slip-and-slide.

• Five years ago we looked at an MMWR: Epidemiological Investigation Into A Case Of Primary Amebic Meningoencephalitis in California which suggested a poorly chlorinated spring-fed swimming pool was the likely source of infection and death of a 21 year old woman.

•  In 2013, in Arkansas: Naegleria fowleri Shuts Water Park, we saw the second suspected case in 3 years from the same recreational venue.

Only 3 or 4 cases are reported in the United States each summer, but in 2017 a research letter written by epidemiologists at the CDC (see EID Journal: Estimation of Undiagnosed Naegleria fowleri (PAM), United States) estimated the yearly number PAM cases in the United States probably averages closer to 16 (8 males, 8 females).

Meaning that 70%-80% likely go unrecognized. But even so, your odds of contracting PAM are exceedingly low.

 Louisiana Health Department report follows:

LDH reports Naegleria fowleri infection in Louisiana resident 

Rare infection most likely acquired while swimming in Lake Claiborne

Baton Rouge, Louisiana, Aug 19, 2026 - The Louisiana Department of Health is reporting a confirmed Naegleria fowleri infection in a Louisiana resident. The resident most likely acquired the infection while swimming in Lake Claiborne, located in Claiborne Parish, shortly before illness.

Naegleria fowleri, often referred to as a brain-eating amoeba, is commonly found in warm freshwater lakes, rivers, canals, and ponds throughout the United States. It can cause primary amebic meningoencephalitis (PAM), a brain infection that may result when water containing the amoeba rushes up the nose and reaches the brain. The infection is extremely rare, but nearly always fatal.

Naegleria fowleri cannot infect people if swallowed and is not spread from person to person. The amoeba is not found in salt water or in properly maintained and chlorinated pools. Symptoms of Naegleria fowleri infection typically start with severe headache, fever, nausea and vomiting and progress to stiff neck, seizures, and coma that can lead to death. Symptoms usually begin about five days after infection but can start within one to 12 days.

Naegleria fowleri thrives in warm, fresh water and grows best at higher temperatures up to 115°F. The amoeba is naturally occurring, and there is no routine environmental test for Naegleria fowleri in bodies of water.

A Health Alert Network (HAN) was shared to all state providers from Louisiana Department of Health on August 18, 2026, advising on symptoms and reporting.

Though the risk of infection is low, recreational water users should always assume there is a risk when they enter warm fresh water. You can reduce your risk of infection by limiting the amount of water that goes up the nose. Recommended precautions include:

• Use caution when engaging in water-related activities in warm freshwater during periods of extended extreme heat. Naegleria fowleri usually occurs when temperatures increase for prolonged periods, resulting in higher water temperatures and lower water levels.
• Swimmers can reduce their risk by keeping their heads out of the water and using nose clips or plugging their noses when going underwater.
• Avoid submersing your head in hot springs and other untreated fresh thermal water.
• Avoid digging in or stirring up the sediment while taking part in water-related activities in shallow, warm freshwater areas.

​Naegleria fowleri infections are rare, with only 180 known cases of PAM in the U.S. (between zero and eight cases annually) from 1937 through 2025. Louisiana had three Naegleria fowleri cases during that time period.

For more information regarding Naegleria fowleri, please visit Naegleria fowleri Infections | Naegleria fowleri Infection | CDC.

For more information on the Naegleria parasite, you can also visit the CDC’s Naegleria webpage.