Viruses: Epidemiological and Virological Characteristics of H9N2 Avian Influenza Virus in Jiangsu Province, China, 2024

Jiangsu Province - Credit Wikipedia

#19,216

It is not exactly a state secret that the Chinese CDC has become increasingly concerned over the evolution and spread of LPAI H9N2 in both poultry and people, particularly in the eastern provinces of China. 

In addition to a human infection reported 10 days ago in Hong Kong, the CHP's latest weekly Avian Influenza report lists 15 known human infections on the mainland over the past 6 months.

While most (but not all) of these reported cases have been mild or moderate, its true incidence and burden in China is unknown. Most people with mild to moderate flu are never hospitalized, or tested, for novel flu. 

Last October the Chinese CDC Weekly published a detailed report (see Epidemiological and Genetic Characterization of Three H9N2 Viruses Causing Human Infections — Changsha City, Hunan Province, China, April 2025) which found:

Three children infected with H9N2 AIV were identified in Changsha in April 2025, and no epidemiological links were found between these mild and sporadic cases. Genetic analysis showed that the H9N2 viruses had enhanced binding ability to upper respiratory tract receptors, particularly the α2,6-sialic acid receptors.

The report goes on describe some of the notable HA mutations suggesting enhanced mammalian adaptation:

Analysis of receptor-binding sites showed that the HA proteins had mutations at amino acid positions H191N, A198V, Q226L, and Q234L, which potentially enhanced the binding ability of the virus to the receptor (5-6).

While there is still no evidence of sustained or efficient human-to-human transmission of H9N2, the virus remains poorly controlled in poultry, and  appears on a path towards greater mammalian adaptation.

LPAI H9N2 continues to evolve and diversify (see EM&I: A new clade of H9N2 avian influenza virus circulating in Laos), and our own CDC has assessed 2 lineages (A(H9N2) G1 and A(H9N2) Y280) as having at least some pandemic potential (see CDC IRAT SCORE).

All of which brings us to a new study, from researchers at several Provincial-level CCDC agencies, which looks at nearly 5,800 environmental samples from live poultry markets, farms, slaughterhouses, and bird habitats in Jiangsu Province in 2024, and finds further evidence of mammalian adaptation. 

They also compared 370 occupationally exposed human sera with 240 non-exposed sera using HI assays, and found a low level of seropositivity in both.

Given the detailed, and highly technical nature of much of this report, I've only posted the Abstract and some excerpts from the Discussion and Conclusion.  Those looking for a deeper dive will want to follow the link to read it in its entirety, but the authors summed up their findings stating:

These findings confirm that Jiangsu’s circulating H9N2 viruses have acquired human receptor preference and mammalian adaptation, posing silent infection and pandemic risks

As you read this, it is worth noting this strongly worded report comes from researchers at China's CDC.  I'll have a bit more after the break.

19 June 2026
Epidemiological and Virological Characteristics of H9N2 Avian Influenza Virus in Jiangsu Province, China, 2024

Xue Gao 1,†, Huiyan Yu 2,†, Na Zhang 3, Liqi Liu 3, Jing Tong 1, Xian Qi 2, Haodi Huang 2, Shenjiao Wang 2, Zi Li 3,* … Liguo Zhu 2,*

Abstract

H9N2 avian influenza viruses inherently carry cross-species transmission potential, making continuous surveillance critical for pandemic prevention. This study focused on monitoring the 2024 H9N2 epidemic in Jiangsu Province’s external environment, analyzing its molecular evolution and receptor binding properties, assessing cross-species transmission and pandemic risks, and investigating serological antibody levels across different human populations.

Environmental samples were collected from live poultry markets, farms, slaughterhouses, and bird habitats across Jiangsu, screened via quantitative PCR (qPCR), with positive samples used for virus isolation and whole-genome sequencing. Receptor binding properties were tested by hemagglutination assay, and H9N2 antibody levels were measured in 370 occupationally exposed individuals and 240 non-exposed individuals using hemagglutination inhibition (HI) assays.

Among the 5779 collected samples, 6.89% tested H9N2-positive, and 12 strains belonging to the Eurasian lineage Y280-like clade G57 genotype were successfully isolated. All strains carried the HA-Q226L mutation, with 11 showing preferential binding to human α-2,6 receptors and one strain possessing dual receptor binding capability.

Internal genes harbored mammalian adaptation mutations, and M2 proteins contained mutations conferring complete resistance to amantadine-class antiviral drugs.Serological tests revealed antibody positive rates of 4.05% in exposed populations and 2.5% in non-exposed populations, with no statistically significant difference between groups.

These findings confirm that Jiangsu’s circulating H9N2 viruses have acquired human receptor preference and mammalian adaptation, posing silent infection and pandemic risks. Enhanced surveillance and the development of candidate vaccine stockpiles are strongly recommended.

 (SNIP)

Notably, dual receptor binding is a key determinant for cross-species transmission and pandemic potential in influenza viruses [21]. Strain CZ3053 not only possessed strong human receptor binding capacity but also retained agglutination activity against horse, sheep, and rabbit red blood cells. Analysis suggests that the HA-V306L mutation may be key for its acquisition of dual receptor binding capability. Amino acid substitution at position 306 may fine-tune the conformation of the receptor binding site through remote allosteric effects, enabling it to maintain avian α-2,3 receptor recognition capacity while further optimizing spatial adaptation to human α-2,6 receptors, thereby acquiring dual receptor binding characteristics.

All isolate PB2 proteins in this study carried a characteristic set of mutations (L89V, L134H, M147I, I292V, R340K, R389K, and A588V) [16]. Among these, M147I and R340K are key molecular markers of the G1-like lineage, closely related to enhanced polymerase activity and replication capacity in mammalian cells [22]. Additionally, combined with the commonly present mutations in PB1 protein (D622G) and PA protein (K356R, S409N, and A515T) related to virulence and polymerase activity, as well as adaptive mutations in NP protein that optimize nuclear transport efficiency (K398Q) and antagonize human restriction factor interference (V352M), these molecular characteristics functionally couple to provide a solid molecular basis for the H9N2 virus breaking through species barriers [23,24,25].

Serological results showed low H9N2 exposure levels in human populations in Jiangsu region in 2024, with no statistically significant difference between occupationally exposed (4.05%) and non-occupationally exposed (2.5%) groups. Based on our findings, H9N2 infection risk may not be limited to occupationally exposed populations, as general residents may also face infection risks through live poultry market environmental exposure or aerosol contact.

Therefore, serological investigation and detection work should be strengthened for different populations. Meanwhile, both positive cases in the non-occupational group were from the adult group, possibly related to higher social activity frequency and environmental exposure opportunities in this age group. Since current antibody levels are far from sufficient to form population immune barriers, accelerating development and application of novel vaccines is a key measure for improving prevention and control effectiveness. 5. 

Conclusions

H9N2 viruses circulating in Jiangsu Province in 2024 have acquired human receptor preference, along with PB2-A588V and other internal gene compensatory adaptations, indicating pandemic potential. It is recommended to conduct continuous surveillance of the H9N2 subtype AIV while accelerating candidate vaccine strain matching and stockpiling work for current circulating branches to respond to potential public health crises. 

       (Continue . . . )

While trying to predict the source of the next influenza pandemic is a mug's game, H9N2 shows up twice the top 10 zoonotic influenza A viruses the CDC has pegged as having at least some pandemic potential, with the Y280 lineage having a higher emergence score than H5N1.

Given that we've already seen 2 modern influenza pandemics (1957 & 1968) caused by avian viruses spilling over from birds to humans in China, it makes sense that China's CDC is taking this threat seriously.

Australia: 2nd H5N1 Infected Bird Confirmed

 
Agriculture Minister Julie Collins Statement

#19,215

Overnight here in the states, Australia's Agriculture Minister and other officials held a press conference and announced the 2nd suspected H5N1 infected bird (Giant Petrel) has been confirmed positive by the CSIRO lab. 

Thus far, only two wild birds - both found in the Cape Le Grand National Park (see map below) - have tested positive. 

For now, Australia's poultry industry has not been affected, and the risk to human health remains low. The public, however, is urged to remain vigilant, and asked to  avoid any physical contact with sick or dead birds and to report sightings to the Emergency Animal Disease Hotline at 1800 675 888.

Animal Health Australia has posted the following update:

Latest emergency response news

Updated: 22 June 2026

H5 high pathogenicity avian influenza (H5 bird flu) has been detected in two wild birds in Western Australia.

The infected birds — a brown skua and a northern giant petrel — were found in the Cape Le Grand National Park, around 50km east of Esperance in Western Australia.

This is the first time the globally circulating H5 bird flu strain has been detected in Australia.

At this stage:

• there have been no detections in poultry
• there is no evidence of any mass mortality in wildlife or spread to other animals 
• there are currently no trade restrictions on poultry or poultry products for export out of Australia.

H5 bird flu is a low health risk to the public and rarely affects humans. Bird flu is not a food safety risk for chicken meat and eggs if they are handled and cooked correctly.

The Western Australia Department of Primary Industries and Regional Development (DPIRD) has responded swiftly to the detection and is leading response activities on the ground. This includes enhanced surveillance, working closely with industry, veterinarians, wildlife carers, and local communities.

National coordination is being led by the Department of Agriculture, Fisheries and Forestry (DAFF).

Further information is available at birdflu.gov.au.

For more background information, The Conversation has published 3 excellent explainers from well known Australian researchers over the past couple of days:

Published: June 22, 2026
What’s the risk of humans getting sick from bird flu?

C Raina MacIntyre, UNSW Sydney and Pan Zhang, UNSW Sydney
The outbreak isn’t widespread, so the risk to humans is low. But it does have the potential to cause severe illness.

Published: June 22, 2026
Bird flu is here. Can we stop the spread?

Jane Younger, University of Tasmania
An ecologist explains how Australia can curb the spread of the H5N1 strain.

Published: June 20, 2026
The first case of H5N1 bird flu in Australia has been confirmed. What does this mean?

Marcel Klaassen, Deakin University; Meagan Dewar, Federation University Australia, and Michelle Wille, The University of Melbourne
This is not the moment to call defeat. There is a chance we can stop this infectious virus, this time at least.

 

USDA Reports 3 More Screwworm Detections (Texas)

 

#19,214

After going more than a week without any new reports, late yesterday the USDA updated their New World Screwworm dashboard to show 3 new detections; 2 (cattle) in Edwards County, Tx, and 1 (sheep) in Crockett County, Tx. 

Previously, Edwards county had reported 2 cases (1 cattle, 1 goats), while this is the first report from Crockett county. 

As discussed previously, the New World Screwworm (NWS) fly lays its eggs in exposed wounds on practically any warm-blooded animal, including birds.  While reported cases remain low, most of our surveillance is among livestock, while infections in the wild go largely unmonitored. 

The CDC describes its life cycle as:

New World screwworm infestations begin when a female fly lays eggs on open wounds or other parts of the body in live, warm-blooded animals. Most infestations occur in animals, but they also occur in people. The smell of a wound or body opening such as the nose, mouth, eyes, ears, or genitals can attract female flies. Wounds as small as a tick bite may attract a female fly to lay her eggs. One female can lay 200 – 300 eggs at a time and may lay up to 3,000 eggs during her 10- to 30-day lifespan.

Eggs hatch into maggots that burrow into the wound to feed on the living flesh. After feeding for about 7 days, larvae drop to the ground, burrow into the soil, and emerge as adult screwworm flies.

The arrival of the NWS this early in the summer maximizes the number of cycles that may occur before winter weather sets in, which greatly limits the spread and survival of the NWS. 

While the USDA continues to release sterile flies in the infested areas, it will take many months - possibly more than a year - to ramp up sterile fly production enough to combat a multi-state outbreak. 

This is only part of the USDA's 8-part plan (see below) to try to contain this threat. 

The ultimate goal is not only to eradicate the NWS in the United States, but also to drive the screwworm back south to its old control line - below the Darien Gap in Panama - to prevent yearly reintroductions from Northern Mexico. 

All of which means winning this battle will likely take years, not months. 

Meanwhile, state veterinarians from as far north as Minnesota are considering their options (see MPR News Minnesota state veterinarian worries New World screwworm could enter the state).

Stay tuned. 

 

(JGR) Cajon Pass and the Southern San Andreas Fault System: Earthquake Cycle Stress Accumulation and Present-Day Loading

 
#19,213

While the United States has enjoyed a bit of an earthquake drought the past century, the good news (and bad) is that all droughts eventually end. 

Exactly where and when that break will occur is unknown, but in 2024 the USGS unveiled a new seismic risk map (see below), increasing the percentage of Americans at risk of experiencing a damaging earthquake to nearly 75% (roughly 240 million people).

Additionally, there are nearly a dozen `very high risk' volcanoes in the continental US (4 in Washington, 4 in Oregon & 3 in California), along dozens of `lesser' threats. While earthquake damage is generally localized, volcanic eruptions can affect property and populations thousands of miles away.

While the next big quake could occur in Alaska, Hawaii, South Carolina, Missouri, or the Pacific Northwest (see FEMA: Cascadia Rising 2016), history and Hollywood have conspired to put California at the top of most people's lists. 

And as we've explored previously, while a truly `Big One' in California would have huge physical impacts locally, it could also be devastating to the entire U.S. economy (see Dr. Lucy Jones: `Imagine America Without Los Angeles’).

Earlier this month the Journal of Geophysical Research: Solid Earth published a paper by a team of international researchers who modeled 1,000 years of earthquake history along two California fault system (Southern San Andreas and San Jacinto) to estimate current stress where they intersect at Cajon Pass.

While this study is getting a lot of - at times hyperbolic - coverage on Social Media and YouTube, the lead author Dr. Liliane Burkhard of the Division of Space Research and Planetary Sciences (WP) at the Physics Institute of the University of Bern stressed that: 

"The study is not a prediction of when an earthquake will occur. What we can say is that the system is critically stressed and that physics-based models like ours give a clearer picture of the range of scenarios we should be prepared for. This information is important for hazard assessment, infrastructure planning and emergency preparedness."

While none of this suggests a big quake is imminent, it does provide a plausible mechanistic description of how one quake could affect two major fault systems, potentially increasing the duration of shaking and the area affected.

First a look at the abstract and summary from the study.  While a lot of this report is technical, many will want to read it in its entirety.

Cajon Pass and the Southern San Andreas Fault System: Earthquake Cycle Stress Accumulation and Present-Day Loading

Liliane M. L. Burkhard, Bridget R. Smith-Konter, Katherine M. Scharer, David T. Sandwell

First published: 03 June 2026 https://doi.org/10.1029/2025JB033213Digital Object Identifier (DOI)  view metrics

PDF

Abstract

With over a century since the last major rupture affecting the wider Los Angeles region, tectonic stress has steadily built along the southern San Andreas and San Jacinto fault systems, raising concerns of an imminent large earthquake. Cajon Pass, located at the junction of these faults, represents a critical site for potential through-going ruptures in Southern California. We constructed new 4D earthquake cycle simulations using a 1000-year paleoseismic rupture history of the San Andreas Fault System (SAFS) to assess spatial and temporal variations in stress. A semi-analytic Fourier transform model was used to compute stress from 3D dislocations in an elastic plate overlying a Maxwell viscoelastic half-space, assuming a complete coseismic reset of resolved shear stress on ruptured elements.

Results show highest stress accumulation north of Cajon Pass (∼1.8 MPa/100 years) due to greater slip rates, and lower rates south of Cajon Pass (∼1.0–1.5 MPa/100 years). By 2025, Coulomb stress is estimated at 2.8 MPa on the Mojave South (MOS) segment, 1.8 MPa on the North San Bernardino (NSB1) segment and 3.6 MPa on the San Jacinto Bernardino (SJB) segment. Segments accumulate stresses with characteristic ranges of pre-event stress interpreted as failure thresholds: 1.2–2.7 MPa for MOS, 0.4–1.6 MPa for NSB1, and 1.2–2.9 MPa for SJB. When the stress disparity between segments SJB and MOS narrows, the faults appear to rupture jointly, suggesting that stress levels may control how Cajon Pass acts as an earthquake gate. These results may inform seismic hazard assessments by linking stress evolution to fault interactions.

Plain Language Summary

Southern California's San Andreas and San Jacinto faults have not produced a major earthquake near Los Angeles in over a century. During that time, tectonic stress has continued to build along these faults, increasing the likelihood of a large future rupture. One key area of concern is Cajon Pass, where the two fault systems meet and could potentially rupture together.

To investigate this, we used computer simulations of the last 1000 years of large earthquake activity to estimate how stress builds up on fault segments and affects neighboring segments over time. The model shows that stress has now reached high levels across the region and that the two fault systems may interact when their stress levels become similar. This suggests that Cajon Pass could act as an “earthquake gate” which sometimes blocks and other times allows large ruptures to propagate between faults. These results improve our understanding of earthquake interactions in Southern California and help refine regional hazard assessments.

       (Continue . . .)


Regardless of whether the next `big one'  occurs on one fault or two, its impact could be substantial, and it is important to be prepared.  Every year since 2009 I've promoted Shakeout.org's safety campaign, and I strongly urge anyone who lives in any seismically active region to take part. 

After the shaking stops, you'll have to find ways to cope with the aftermath. 

While the government will send help, you could find yourself pretty much on your own for several days and living in less than comfortable conditions for weeks.

For starters - and as a bare minimum - every household should have a disaster plan, a good first aid kit (and the knowledge to use it), an emergency battery operated NWS weather radio, and emergency supplies to last a minimum of 72 hours during a disaster.

While 72 hours is an admirable start, having previously lived very near the New Madrid fault, and now living in hurricane country, I wouldn't feel comfortable stopping there.

Many agencies and organizations in the U.S. recommend that households work towards having a 10-to-14 day supply of food, water, and emergency supplies on hand, which I consider far more prudent.

For more on earthquake preparedness, both here in the United States, and around the world, you may wish to revisit:

Japan's Earthquake Preparedness Messaging - Tokyo's X Day

California Quakes : Concrete Concerns

Estimating The Economic Impact Of A San Andreas Quake

Australia: HPAI H5 Confirmed For First Time (Brown Skua)

 

 

#19,212

Overnight the Australian Government confirmed what was broadly expected; that HPAI H5N1 has now been detected in a migratory bird in Australia.  Reports also  indicate that a second bird (Giant Petrel) has also tested presumed positive. 

You'll find Ian Mckay's latest blog post here, and I've reproduced the official announcement from DAFF (Department of Agriculture) below.

H5 bird flu confirmed in Australia
20 June 2026

Testing at CSIRO’s Australian Centre for Disease Preparedness (ACDP) has confirmed H5 high pathogenicity avian influenza (bird flu) in a brown skua in Western Australia.

This is the highly pathogenic strain of concern that has been circulating globally, and is the first detection in Australia.

Samples from a second bird, a giant petrel, have also tested positive for H5 avian influenza at the Western Australian Department of Primary Industries and Regional Development’s laboratory.

These samples will now also undergo confirmatory testing at CSIRO’s ACDP.

These species are migratory seabird species that occasionally visit southern Australia.

Both species were found in an isolated area in a national park near Esperance, and were cared for in isolation.

The Western Australia Department of Primary Industries and Regional Development is leading on-ground activities and the Department of Agriculture, Fisheries and Forestry is supporting national coordination.

A key priority is to undertake surveillance to determine the extent of the infection in wildlife.

There have been no detections in poultry and there is no evidence of mass mortality at this time.

Australia’s response is designed to manage the risks of H5 bird flu, to protect poultry production, and reduce impacts on wildlife and communities.

More than $113 million has been invested by the Albanese Government to strengthen our nation’s preparedness for H5 bird flu.

A dedicated Australian Government Taskforce was established in 2024 to strengthen preparedness for a possible incursion, jointly led by the Department of Agriculture, Fisheries and Forestry, Department of Climate Change, Energy, the Environment and Water, the Australian Centre for Disease Control on behalf of the Department of Health, Disability and Ageing and the National Emergency Management Agency.

A series of national simulation exercises have also been undertaken since 2024 to prepare for this event.

Government, industry and stakeholders have been working together to strengthen planning and governance arrangements for disease response and are ready to activate.

H5 bird flu is a low health risk to the public as it rarely affects humans unless there is direct and close contact with sick birds. Eggs and poultry meat are safe to eat provided they are handled and cooked according to standard food-safety practices.

H5 bird flu causes severe illness and high death rates in birds.

In birds, the disease can cause sudden death, a sharp drop in egg production, swelling of the head and neck, breathing difficulties, and sometimes neurological signs such as loss of coordination.

The community is encouraged to report any dead or sick birds or animals showing signs of bird flu.

If you see multiple sick or dead birds or other animals, do not touch them. Avoid contact. Record what you see. Report it to the Emergency Animal Disease Hotline on 1800 675 888 from anywhere in Australia.

For more information visit: birdflu.gov.au

Although remains to be seen how much of an impact this first arrival will have on Australia, and the rest of the world, this is once again proof (as if we needed it) that the HPAI H5 viruses of today are vastly improved versions of what was circulating even a decade ago. 

Over the past 5 years we've seen HPAI H5 spread extensively across North and South America - and the Antarctic - while at the same time expanding its host range among both land and marine mammals. 

While past performance is no guarantee of future results, HPAI's current trajectory is far from comforting. 

Idaho Health HAN: Consider Avian Influenza A (H5N1) in Patients with Dairy Cattle or Poultry Exposure

 

#19,211

While reporting of HPAI H5 in dairy herds has slowed in 2026, we continue to see scattered outbreaks, with the most pronounced currently in the state of Idaho. 

Similarly, we've not seen a human H5N1 case reporting in the United States in more than a year, but serological testing suggests some mild or asymptomatic cases may be flying under the radar. 

Detection is highly dependent upon clinicians maintaining an elevated index of suspicion, and their willingness to order HPAI H5 specific tests. As we've seen often (see QJM: Avian Influenza in Humans: Virology, Transmission, and Clinical Priorities) the diagnosis is often missed - or at least delayed - even in hospitalized cases. 

This past week, with the increase in outbreaks in Idaho's dairy herds, their Central District Health agency issued the following HAN Health Advisory:

Health Advisory: Consider Avian Influenza A (H5N1) in Patients with Dairy Cattle or Poultry Exposure

by Trent Young on June 16, 2026


HEALTH ALERT NETWORK – Health District 4

Advisory for Healthcare Providers: Consider Avian Influenza A (H5N1) in Patients with Dairy Cattle or Poultry Exposure

Key Messages

Local Situation: Avian Influenza A (H5N1) has been confirmed in over 80 Idaho dairy premises, including 12 in District 4 currently under ISDA quarantine.

Clinical Suspicion: Consider H5N1 infection in patients presenting with conjunctivitis or acute respiratory illness who report recent exposure to dairy cattle, sick poultry, or contaminated environments.

Report Immediately: Novel influenza A infections are immediately reportable. Contact CDH at 208-327-8625 to report suspected cases.

Occupational Risk: While the risk to the general public remains low, agricultural workers and others with direct animal exposure are at increased risk.

Background and Current Situation

Due to ongoing H5N1 detections in Idaho dairy herds and continued circulation in poultry, clinicians should consider H5N1 in patients with compatible illness and relevant exposure histories.

Since its detection in U.S. dairy cattle in March 2024, H5N1 has spread to more than 1,100 dairy herds across at least 20 states. There have been 71 reported human cases in the U.S. since 2024, most associated with dairy cattle exposure and direct contact with infected animals or contaminated milk. No human cases have been reported in Idaho. Most U.S. infections have been mild and characterized by conjunctivitis, although respiratory illness and severe disease can occur. There is no evidence of sustained person-to-person transmission.

Individuals at increased risk of exposure include:

• Dairy farm workers and milkers
• Veterinarians and animal health personnel
• Farm support staff (cleaning, transport, equipment handling)
• Household contacts of exposed workers

Clinical Presentation

Mild / Typical Illness:

• Conjunctivitis (redness, irritation, discharge, foreign body sensation)
• Fever, cough, sore throat, rhinorrhea
• Fatigue, headache, myalgia, arthralgia
• Gastrointestinal symptoms

Moderate to Severe Illness:

• Shortness of breath
• Altered mental status or seizures
• Pneumonia, ARDS, sepsis, multi-organ failure

Asymptomatic Testing:

Consider testing asymptomatic individuals with high-risk exposures (e.g., exposure to infected animals without recommended PPE or after a PPE breach). Collect respiratory and conjunctival specimens as recommended.

Laboratory Testing and Specimen Collection

• Idaho Bureau of Laboratories (IBL) Submission:
• Order Name: Influenza Subtyping
• Aliases: Flu A/B PCR, Flu A subtyping, H5N1, HPAI
• Commercial Lab Availability for Influenza A (H5):ARUP: Respiratory or conjunctival swabs
• LabCorp: Nasopharyngeal (NP) swabs only
• Quest: NP, nasal, OP, BAL, or conjunctival swabs

Standard Specimen Collection:

• Nasopharyngeal (NP) swab in one viral transport medium (VTM) tube
• Nasal and oropharyngeal (OP) swabs combined in a second VTM tube
• If conjunctivitis is present, collect a conjunctival swab in a separate VTM tube
• For severe illness, collect lower respiratory specimens (e.g., bronchoalveolar lavage or endotracheal aspirate) when feasible
• Rapid influenza diagnostic tests have limited sensitivity and should not be used to rule out H5N1 infection

Handling and Transport

• Coordinate specimen collection and submission with Central District Health before shipping.
• Store specimens:2–8°C for up to 72 hours, OR
• ≤ −20°C for longer storage (up to 30 days)
• If frozen:Do NOT thaw before testing
• Ship on dry ice for overnight delivery
• If refrigerated, transport promptly on cold packs

Antiviral Treatment and Prophylaxis

Do NOT delay treatment while awaiting results.

• Initiate oseltamivir 75 mg orally twice daily for 5 days for symptomatic adolescents and adults with suspected H5N1 infection. Refer to CDC guidance for pediatric dosing.
• Consider post-exposure prophylaxis for individuals with high-risk exposures, using recommended treatment dosing for 5 or 10 days, depending on the exposure scenario.

Central District Health Contact: 208-327-8625

Resources

Avian Influenza (Bird Flu): Highly Pathogenic Avian Influenza A(H5N1) Virus: Interim Recommendations for Prevention, Monitoring, and Public Health. CDC.gov Updated December 26, 2024. Accessed January 09, 2026.
https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html
Emergency Use Instructions (EUI) Fact Sheet for Healthcare Providers: Oseltamivir for Treatment or Post-Exposure Prophylaxis of Novel Influenza A. February 18, 2025. https://www.cdc.gov/bird-flu/media/pdfs/2024/07/Oseltamivir-EUI-HCP_1.pdf
Avian Influenza (Bird Flu): Interim Guidance on Specimen Collection and Testing for Patients with Suspected Infection with Novel Influenza A Viruses Associated with Severe Disease or with the Potential to Cause Severe Disease in Humans. CDC .gov. Updated May 15, 2025. Accessed January 09, 2026. https://www.cdc.gov/bird-flu/php/severe-potential/index.html

While most known human H5 infections have been epidemiologically linked to a specific agricultural exposure (cows, chickens, wild birds, etc.), over the past 2 years we've seen a handful (U.S. x 4, Mexico x 3, Canada x 1) where the source of exposure remains unexplained.

Given the limits of surveillance and testing, it would not be terribly surprising if there are other cases in the community that have not been officially confirmed.

Particularly since some percentage of infections are asymptomatic or very mild (see MMWR: Serologic Evidence of Recent Infection with HPAI A(H5) Virus Among Dairy Workers).

Three years ago, in UK Novel Flu Surveillance: Quantifying TTD, we looked at a UKHSA report that it would likely take between 3 and 10 weeks before community spread of a novel flu virus would become apparent to authorities, after anywhere between a few dozen to a few thousand community infections

Anything we can do to shorten those delays could pay important dividends should HPAI take off.