Washington: Tacoma-Pierce County Health Dept. Investigating Possible Locally Acquired Case of Malaria

Credit Martin County Health Department

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Although roughly 2,000 travel-related cases of Malaria are reported each year in the United States, locally acquired cases have been quite rare in this 21st century.  If we go back a hundred or so years, however, Malaria was still fairly widespread. 

Fifteen years ago, in Florida: Locally Acquired Malaria Case Suspected, we looked at a rare case in a resident of Jacksonville with no history of international travel. In 1996 (2 cases) and again in 2003 (8 cases) of locally acquired P. vivax malaria were detected in Palm Beach County (see Multifocal Autochthonous Transmission of Malaria --- Florida, 2003).

More recently, in June of 2023 (see CDC HAN: Locally Acquired Malaria Cases Identified in the United States) local transmission of Malaria was reported in 2 different states. Two months later, a 3rd state (Maryland) reported a single case. 

While the risks of acquiring Malaria are quite low, they aren't zero.  

Most viral (and parasitic) infections have at least a 3 to 15 day incubation period, giving infected travelers a fairly long asymptomatic `window' in which to travel. Should a viremic visitor be bitten by a competent local vector, there is the possibility the disease may be transmitted on to others. 

Which is likely how a local resident in Washington State came to be infected with Malaria, as reported in the following press release from the Tacoma-Pierce County Health Department.

First the announcement, after which I'll have a bit more on the importation of vector-borne diseases. 

We are investigating possible locally acquired case of malaria

August 6, 2025

The risk to the public is very low.

An East Pierce County woman who has not traveled recently was diagnosed Aug. 2 with malaria. She is receiving treatment and we continue to monitor her status.

We are working with Washington State Department of Health (DOH) and Centers for Disease Control and Prevention (CDC) to investigate potential sources of infection. It’s possible she was recently infected with malaria in Washington. If confirmed, this would be the first known locally acquired case of malaria in Washington.

The most likely cause of a locally acquired case is a mosquito biting someone infected with a travel-associated case of malaria, then passing the infection on to this patient.

“The risk of getting infected with malaria in Pierce County remains very low,” said Dr. James Miller, Tacoma-Pierce County Health Officer. “Malaria is a rare disease overall in the United States—and the vast majority of cases in the United States occur following exposures in countries with ongoing transmission.”

Malaria is a mosquito-borne disease caused by a parasite. It typically causes fever, chills, body aches, headaches, and fatigue. It can also cause nausea, vomiting, and diarrhea. In most cases, the incubation period—the time between infection and start of symptoms—is 7-30 days. Malaria does not spread directly from one person to another.

Malaria can be cured with prescription antimalarial drugs. It can be life-threatening if is not diagnosed and treated quickly.

The U.S. sees about 2,000–2,500 and Washington sees about 20-70 reports of malaria cases each year linked to travel. In 2023, the United States experienced its first locally acquired mosquito-transmitted malaria case in 20 years. Between May 2023–October 2023, 10 cases were reported across four states.

The Anopheles mosquitoes that transmit malaria live across the U.S. If they bite someone infected with malaria, they may become infectious and could transmit the parasite to people in the area.

As part of the investigation, we are working with DOH to implement mosquito trapping and testing. Fortunately, at this time of year mosquito populations in Pierce County are decreasing.

The best way to prevent malaria is to prevent mosquito bites and ensure early diagnosis and treatment of cases in returning travelers. Use an EPA-registered insect repellent and wear long sleeved clothing when spending time in areas with mosquitoes and use screens on windows and doors. Remove and reduce places where mosquitoes can breed by removing or covering sources of standing water like birdbaths, animal troughs, pools, tires, or other places where water may collect.

Travelers to countries where malaria is more common should take steps to prevent acquiring malaria. That sometimes includes taking medications to prevent malaria. Contact a healthcare provider before traveling to see if you need to take medications to prevent malaria. If you develop symptoms of malaria, contact a healthcare provider right away.

This situation also highlights the importance of a prepared and coordinated public health system that is ready to respond to urgent communicable disease investigations. We are grateful to our partners at DOH and CDC for their assistance with various aspects of this investigation. We also rely on healthcare workers to recognize and report rare diseases to public health and thank the astute clinicians who diagnosed this person.

About Tacoma-Pierce County Health Department: Tacoma-Pierce County Health Department’s mission is to protect and improve the health of all people and places in Pierce County. As part of our mission, the Health Department tackles known and emerging health risks through policy, programs, and treatment to protect public health. Learn more at tpchd.org.

While this is likely an isolated incident, over the past 20 years we've kept watch on the steady spread of vector-borne diseases - like Dengue, Zika, Malaria, and Chikungunya - around the globe. 

Nations that were once considered free of these exotic diseases now battle outbreaks on a regular basis. 

Before 1999, the United States was free from the West Nile Virus.  By 2005, the virus has spread nationwide. In 2009 Dengue returned to Florida (see MMWR: Dengue Fever In Key West) after an absence of roughly 60 years, likely carried in by an infected traveler. 

Chikungunya - which is currently sparking a serious epidemic in China (see FluTrackers Thread) - was first introduced to the Caribbean in 2013, and is now a serious concern in South America. 

As we've discussed previously (see EID Journal: Hx of Mosquito borne Diseases In the U.S. & Implications For The Future), at one time epidemics of  Malaria and Yellow Fever were rife in the U.S. as far north as New England.

And with recent reports of  A Widespread Super–Insecticide-Resistant Aedes aegypti Mosquito in Asia, we'll need to find new and better ways to control these mosquito vectors, if we are to stay ahead of these growing 21st century threats.

While it might not be at the top of your list of stock up items for your Hurricane/Disaster kit, having mosquito repellent for you and your family is highly recommended.

For some earlier mosquito-borne illness blogs, you may wish to revisit:

CDC HAN #00523: Ongoing Risk of Dengue Virus Infections and Updated Testing Recommendations in the United States

CDC Vital Signs - Zika Virus Update

Arboviruses: (Already) Coming To America

Grand Rounds: Preventing Aedes Mosquito-Borne Diseases

PNAS: Asymptomatic Humans Transmit Dengue Virus To Mosquitoes

Pandemic NPIs & Fluid Dynamical Pathways of Airborne Transmission While Waiting in a Line

 
Breath `plumes' while in a queue

#18,828

Regardless of what pathogen sparks the next pandemic, the public's first line of defense - at least during the opening months - will be NPIs; Nonpharmaceutical Interventions. 

We'll undoubtedly be told to avoid crowds, wash our hands, stay home if we're sick, and to cover our coughs.  Many shops and queues will institute a 6-foot separation policy, and - assuming they are available - face masks may once again come back into fashion.  

And while all of these are useful common-sense suggestions - and will be heavily touted by public health officials desperate to provide `something' to the public - exactly how much protection each individual action might afford is debatable. 

• Washing (or disinfecting) hands is always good practice, even outside of a pandemic scenario. But most pandemics are caused by respiratory viruses, limiting the impact of handwashing (see Efficacy Of Hand Hygiene Alone Against Influenza Infection).

• Covering coughs (sneezing into elbows, tissue, or hand etc.) may redirect the spread of viruses, but may do little actually reduce it (see Study: Simulating the Environmental Spread of SARS-CoV-2 via Cough and the Effect of Personal Mitigations).

• And while staying home when sick is excellent advice, many respiratory viruses can be spread asymptomatically or by pre-symptomatic individuals (see EID Journal: Asymptomatic or Presymptomatic Transmission Of SARS-CoV-2).

The good news is that while individually the evidence is weak supporting their ability to reduce the risks of infection during a respiratory pandemic - when combined  or layered - their impact is significantly magnified. 

Dr. Ian McKay's famous `Swiss Cheese' analogy (below) illustrates the power of a layered defense. 

In the first year of COVID - despite growing evidence to the contrary - many public health agencies continued to treat SARS-CoV-2 as if it was a spread primarily by large droplets. 

The CDC's definition of a `close contact' to an infected individual read:

Someone who was within 6 feet of an infected person for at least 15 minutes starting from 2 days before illness onset (or, for asymptomatic patients, 2 days prior to specimen collection) until the time the patient is isolated.

 

Many people assumed that this meant `6 feet was a  safe distance', but there was scant scientific evidence behind it.  By mid-2021 the CDC's updated scientific brief  allowed that `Transmission of SARS-CoV-2 from inhalation of virus in the air farther than six feet from an infectious source can occur.'

While the transmission dynamics of the next pandemic virus could be far different from what we saw with COVID, now - during our interpandemic period - is the time to improve our understanding of the effectiveness of NPIs (individually and in concert).

To that end we have a fascinating, but at times quite technical, research article published in Science Advances that attempts to better understand how airborne virus plumes spread; particularly in a moving queue. 

What they found was the dynamics of aerosol plumes are far more complex in a moving queue than during a static encounter. Warm exhaled air normally rises (buoyancy), but forward movement can cause downwash currents. 

Researchers report that intermediate ambient temperatures (22-30°C) and the walking/moving speed of the queue can combine to increase the risk of transmission, causing infectious aerosols to linger at head height with minimal dilution, writing:

The findings presented here highlight the stark contrast to the transmission mechanisms in static social interactions, where flows generated by the kinematics of individuals are absent.

I've reproduced the abstract, and some excerpts from a press release from the University of Massachusetts Amherst. Follow the links to read them in their entirety.   

I'll have a bit more after you return. 

Fluid dynamical pathways of airborne transmission while waiting in a line

Ruixi Lou, Milo Van Mooy, Gabriel A. Tarditti https://orcid.org/0009-0003-6692-5372, Rodolfo Ostilla Monico https://orcid.org/0000-0001-7049-2432, and Varghese Mathai
Science Advances 6 Aug 2025 Vol 11, Issue 32
DOI: 10.1126/sciadv.adw0985

Abstract

Waiting in a line (or a queue) is an unavoidable social interaction that occurs frequently in public spaces. Despite its wide prevalence and rich parametric variability, few studies have addressed the risks of airborne infection while waiting in a line.

Here, we use a combination of laboratory experiments and direct numerical simulations to assess the flow patterns in a simplified waiting line setting. From observations of the transport of breath-like expulsions, we reveal the presence of fluid dynamical counter-currents —due to the competing effects of line kinematics and thermal gradients.

Depending on the walking speed, an intermediate temperature range can potentially heighten the infection risks by allowing the breath plume to linger; however, colder and warmer ambients both suppress the spread.

Current guidelines of increasing physical separation appear to have a limited impact on reducing aerosol transmission. This work highlights the need for updated transmission mitigation guidelines in settings where physical separation, interaction duration, and periodicity of movements are factors.

        (Continue . . .)
 

Waiting in line: Why six feet of social distancing may not be enough

Study, led by undergraduate physics majors at UMass Amherst and researchers at University of Cadiz, sharpens our understanding of how airborne-communicable diseases travel

University of Massachusetts Amherst
Credit: Lou et al., 10.1126/sciadv.adw0985

August 6, 2025

AMHERST, Mass.

(Excerpt)

The results, published recently in Science Advances, grew out of a question that many of us may have asked ourselves when standing in marked locations six-feet apart while waiting for a vaccine, to pay for groceries or to get a cup of coffee: what’s the science behind six-feet of separation? If you are a physicist, you might even have asked yourself, “what is happening physically to the aerosol plumes we’re all breathing out while waiting in a line, and is the six-foot guideline the best way to design a queue?”

(SNIP)

“What we found was really surprising,” says Van Mooy.

Since warm air rises, there is a slight updraft surrounding our bodies—and so the team expected to see the aerosol plumes rising. But instead, they observed a “downwash” effect, where the simple act of walking and waiting in a line caused the plumes to sink. Even more surprising was that, if the ambient temperature is close to our body temperature, as would be the case in a non-air-conditioned room in summer, those aerosols could be pushed toward the floor due to air currents.

However, in a climate-controlled room, the difference in temperature between what we exhale and the ambient conditions are enough to drive those plumes aloft. If the temperature is in an intermediate range, it is quite possible that the aerosols can hover at just the right height for the next person in the line to inhale them as the line moves forward.

“Ultimately, there are no hard-and-fast rules about social distancing that will keep us safe or unsafe,” says senior author Varghese Mathai, assistant professor of physics at UMass Amherst. “The fluid dynamics of air are marvelously complex and general intuition often misleads, even for something as simple as standing in a line. We need to take space and time into account as we come up with our public health guidelines.”

        (Continue . . . )


While I expect that keeping a 2-meter distance from others in line is safer than maintaining only a 1-meter gap, it is not a difference I'd be willing to bet my life on during the next pandemic.  

A `layered' NPI approach will provide the most protection, but for that you'll need to be well prepared before a threat becomes obvious. 

For some tips what you and your family can do now to prepare for the next global health crisis, you may wish to revisit A Personal Pre-Pandemic Plan.

Cambodian MOH Announces 15th H5N1 Case of 2025

 

#18,827

It's been just over a week since the last case was reported by Cambodia, and the summer surge in cases continues with the 12th case reported since late May (and 31st since this resurgence began in early 2023).   

Unlike H5N1 cases reported in the United States - which are due to a milder clade 2.3.4.4b - recent Cambodian cases have been caused by a new reassortment of an older clade of the H5N1 virus (recently renamed 2.3.2.1e) - which appears to be spreading rapidly through both wild birds and local poultry.

This morning the Cambodia MOH posted an announcement on their Facebook page on another H5N1 case - this time from Takeo Province - involving a 6 year old child who is reportedly in intensive care reportedly being exposed to sick or dead chickens.

I've reproduced the screen shot (in Cambodian) and have provided an English translation below.

        (Translation)

Kingdom of Cambodia, Nation, Religion, King

Ministry of Health

Press Release

Cases of bird flu in 6-year-old girls

The Ministry of Health of the Kingdom of Cambodia would like to inform the public that there is another case of bird flu in a 6-year-old girl who was confirmed positive for the H5N1 bird flu virus by the National Institute of Public Health on August 5, 2025. The patient lives in Prey Mok village, Sre Nong commune, Tram Kak district, Takeo province. He has symptoms of fever, cough, fatigue and difficulty breathing. 

The patient is currently undergoing rescue efforts with the attention of doctors. According to the survey, a month ago, in the village, there were nearly a thousand sick and dead chickens. At the children's house, during the 20 days, there were 30 sick and dead chickens in a row, and the child's mother brought the dead chickens to cook before the day the children started to get sick.

The Ministry of Health's national and sub-national emergency response teams have been working closely with provincial agriculture departments and local authorities to actively investigate the outbreak of bird flu and respond to methods and technical protocols, identify sources of transmission in both animals and humans, and identify suspected and affected cases in the community.

The Ministry of Health would like to remind all citizens to be careful of bird flu because H5N1 bird flu continues to threaten the health of our people, and also to inform you if you have a fever, cough, runny nose or shortness of breath and have a history of contact with sick or dead chickens during the 14 days before the onset of symptoms and people do not go to the meeting. Seek medical treatment at a nearby health center or hospital immediately to avoid delays, leading to a higher risk of eventual death.

Transmission: H5N1 bird flu is a flu virus that is usually transmitted from sick birds to other birds, but can sometimes be transmitted from birds to humans through close contact with sick or dead birds. Avian influenza in humans is a serious disease that requires timely hospitalization. Although it is not easily transmitted from person to person, if it can metabolize it can be as contagious as the seasonal flu.

Address: Lot 80, Samdech Pen Nuth Street (289)

Phone: (+855) 23 885 970

Sangkat Boeung Kak II, Khan Toul Kork, Phnom Penh

Email: info@moh.gov.kh

Website: www.moh.gov.kh

Telegram: t.me/MOHCambodia

As we discussed a month ago, in Cambodia: Food Insecurity, Food Safety & H5N1 - despite repeated warnings to the public not to prepare or cook sick/dead poultry - scarce resources and hunger can sometimes drive people to take risks.

Given the frequent contacts reported with sick or dead poultry, there is currently no evidence to suggest human-to-human transmission of the virus.

While we continue to focus on clade 2.3.4.4b H5 viruses in the United States, this case reminds us that there are many other iterations of HPAI H5 viruses circulating around the globe - with new ones emerging at an increasing rate - each on their own evolutionary trajectory.

EID Journal: Attachment Patterns of Avian Influenza H5 Clade 2.3.4.4b Virus in Respiratory Tracts of Marine Mammals, North Atlantic Ocean

Flu Virus binding to Receptor Cells – Credit CDC

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We've known for over 4 decades that marine mammals (seals, whales, dolphins, etc.) are susceptible to influenza A viruses (see 1984's Are seals frequently infected with avian influenza viruses? by Webster et al.), and over the past 20 years have looked a number of unusual mortality events (UMEs). 

• In November of 2011 a die off of seals in New England that was eventually tied to an H3N8 avian Flu Virus. 2012's mBio: A Mammalian Adapted H3N8 In Seals, presented evidence that this virus had recently adapted to better bind to alpha 2,6 receptor cells, the type found in the human upper respiratory tract.

• A large outbreak was reported from northern Europe (mostly Denmark and Germany & Sweden) in 2014, when as many as 3,000 harbor seals reportedly died from avian H10N7 (see Avian H10N7 Linked To Dead European Seals), prompting warnings to the public not to touch seals.
• In 2017, during the HPAI H5N8 epizootic in Europe, that emerging subtype (clade 2.3.4.4.B) was found in Grey seals in the Baltic Sea (see EID Journal: Highly Pathogenic Avian Influenza A(H5N8) Virus in Gray Seals, Baltic Sea).

While some outbreaks have likely gone unreported, it wasn't until 2017 that an HPAI H5 virus (H5N8) was detected in marine mammals (see above). The big surge, however, began in 2020, after the changeover from H5N8 to H5N1:

Two Reports On HPAI H5N8 Infecting Marine Mammals (Denmark & Germany)

UK: HAIRS Risk Assessment On Avian Flu In Seals (2022)

Quebec: Seal Deaths Linked To Avian H5N1

Chile: SERNAPESCA Reports A Record Number of Marine Strandings In 1st Quarter of 2023

EID Journal: Mass Mortality of Sea Lions Caused by HPAI A(H5N1) Virus (Peru)

Preprint: Massive outbreak of Influenza A H5N1 in elephant seals at Peninsula Valdes, Argentina: increased evidence for mammal-to-mammal transmission

Not only have tens of thousands of marine mammals died from HPAI H5 over the past 5 years, there is growing evidence that some species can transmit the virus from mammal-to-mammal (see Nature Comms: Cross-species and mammal-to-mammal transmission of clade 2.3.4.4b HPAI A/H5N1 with PB2 adaptations).

Since 2020 we've seen HPAI H5N1 dramatically increase both its geographic and (avian & mammalian) host range, as well as producing increased neurological manifestations (see Cell: The Neuropathogenesis of HPAI H5Nx Viruses in Mammalian Species Including Humans) in some hosts.

Simply put, the H5Nx virus of today is a far cry from the H5Nx of 2005, or even 2019. And those changes are likely to continue. 

Today we've a research paper published in the EID Journal which suggest that these changes may be linked to changing viral cell tropism favoring lower respiratory tracts in some mammals.  

Among their key findings:

• Researcher found both the 2005 and 2022 H5N1 viruses attached readily to upper respiratory tract tissues in seals
• But the 2022 clade 2.3.4.4b virus showed significantly increased affinity for  lower respiratory tract tissues as well 
• Additionally, seals showed greater susceptibility than cetaceans (porpoises and dolphins)

Due to its length, I've only posted the abstract a few excerpts. Follow the link to read it in its entirety.  I'll have a bit more after the break. 

Attachment Patterns of Avian Influenza H5 Clade 2.3.4.4b Virus in Respiratory Tracts of Marine Mammals, North Atlantic Ocean

Syriam Sooksawasdi Na Ayudhya1, Lonneke Leijten, Willemijn F. Rijnink, Monique I. Spronken, Thijs Kuiken, Lisa Bauer2, and Debby van Riel2

Abstract

Highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus infections have caused substantial mortality events in marine mammals in recent years. We hypothesized that the high number of infections and disease severity could be related to cell tropism in respiratory tracts. Therefore, we examined the attachment pattern of an H5N1 clade 2.3.4.4b virus (H52022) as a measure for cell tropism in the respiratory tracts of harbor seals, gray seals, harbor porpoises, and bottlenose dolphins and compared it with an H5N1 clade 2.1.3.2 virus (H52005) and a human seasonal H3N2 virus using virus histochemistry.

Both H5 viruses attached abundantly to olfactory and respiratory mucosa in the upper respiratory tract of both seal species. H52022 attached more abundantly than H52005 to epithelial cells in the lower respiratory tract of all species. The observed attachment possibly explains the susceptibility of marine mammal species for recent H5N1 viruses and the observed development of severe disease.

(SNIP)

The ability of HPAI H5N1 clade 2.3.4.4b viruses to infect and cause severe disease in a broad range of mammal species has not been previously observed with other avian influenza A viruses (3,34).

The attachment pattern in the respiratory tract of marine mammals of H5N1 clade 2.3.4.4b virus, and whether that pattern differs from the attachment pattern of previously circulating H5 viruses from different clades, is unknown. Therefore, we compared the attachment pattern of a 2022 H5N1 clade 2.3.4.4b virus, a 2005 H5N1 clade 2.1.3.2 virus, and a seasonal human H3N2 virus in the respiratory tracts of marine mammals commonly found in the North Atlantic Ocean: harbor seals, gray seals, harbor porpoises, and bottlenose dolphins.

       (SNIP)

Discussion

We describe the attachment patterns of HPAI H5N1 viruses in the respiratory tracts of common North Atlantic marine mammals. Our study revealed that avian H5 viruses attach abundantly to the upper respiratory tract of harbor seals and gray seals. In the lower respiratory tract of harbor seals, gray seals, and harbor porpoises, the recent H5N1 clade 2.3.4.4b virus attaches more abundantly than an H5N1 clade 2.1.3.2 virus from 2005.

(SNIP)

Several studies have shown that recent H5N1 clade 2.3.4.4b viruses, including bovine isolates, preferentially bind to α2,3-linked sialic acid receptors (41,45–47). The variability in attachment between the 2 H5N1 virus clades in our study are therefore likely not the result of a receptor switch to 2,6-linked sialic acid but potentially because of the amino acid differences in or close to the receptor-binding site, known to affect receptor specificity or affinity. However, the exact role of the individual amino acid positions remains to be investigated

Both HPAI H5N1 viruses (either of clade 2.3.4.4b or clade 2.1.3.2) and H3N2 virus attach to olfactory mucosa in the nasal cavity of gray and harbor seals. Neurologic complications are regularly observed in marine mammals infected with H5 viruses, and virus can be detected in high titers in the brain (19,21,23,24,28).

How H5 viruses enter the central nervous system remains unclear, but observations suggest that the viruses can enter the central nervous system via the olfactory nerve in seals, as observed in experimentally inoculated ferrets (48–50). However, HPAI H5N1 viruses can also invade the central nervous system in ceteceans, which lack a olfactory mucosa, so neuroinvasion likely could also occur via other cranial nerves or the hematogenous route (28).

In conclusion, our study highlights changes in the attachment pattern of a recent HPAI H5N1 clade 2.3.4.4b virus compared with H5N1 clade 2.1.3.2 virus from 2005 in the respiratory tracts of 4 marine mammal species that could lead to more efficient transmission and more severe disease.

That finding, together with the recent increase in HPAI H5N1–associated deaths in marine mammals worldwide, emphasizes the need for increased avian influenza surveillance and research in such marine mammal species to limit illness and deaths and help protect both animal and human health.

Dr. Sooksawasdi Na Ayudhya is an instructor and researcher at the Faculty of Veterinary Science, Prince of Songkla, Songkhla, Thailand. Her main interests are pathogenesis and molecular epidemiology of viral infectious diseases and viral emerging infectious diseases in humans and animals.

       (Continue . . . )


Not so very long ago conventional wisdom held that for HPAI H5N1 to pose a genuine human pandemic threat, it would need to change its preference for avian α2,3-linked receptor cells to mammalian α2,6-linked receptor cells.

And while that may still be true, there are hints in this study that other genetic changes in (or near) the RBD (Receptor Binding Domain) of the virus may enable avian α2,3 binding viruses to better infect mammals.

We've seen other examples of `permissive mutations' that can counteract the effects of existing genetic traits (see Virus Research: A 15-year Study of Neuraminidase Mutations and the Increasing of S247N Mutation in Spain). 

Today's report is reminder that the HPAI H5 virus of today is not the same H5N1 virus that threatened - but failed - to produce a pandemic 20 years ago. 

If the past 18 months have taught us anything, it is that the HPAI H5Nx virus is rapidly evolving on multiple fronts - and while that doesn't guarantee a more formidable virus in the future - the trajectory we are seeing is far from reassuring. 

Svalbard: HPAI H5N5 Detected In Arctic Foxes

Location of Svalbard in the Arctic Ocean

#18,825

While H5N1 clade 2.3.4.4b is currently the dominant HPAI strain around the globe, older clades (2.3.2.1a in India and 2.3.2.1e in Cambodia) continue to circulate and occasionally spill over into humans. 

Additionally, China has reported > 90 human infections with a different subtype; H5N6 (clade 2.3.4.4x), and we've been closely watching the spread of HPAI H5N5 in both Eastern Canada, and Northern Europe. 

Credit: Multiple transatlantic incursions of highly pathogenic avian influenza clade 2.3.4.4b A(H5N5) virus into North America and spillover to mammals

In the summer of 2022, the Norwegian Veterinary Institute reported both H5N1 and H5N5 for the first time in wild birds on Svalbard, which lies above the Arctic circle (see More HPAI (H5N5 & H5N1) Detected In Arctic (Svalbard). 

Since then we've been tracking a small - but growing - number of spillovers of H5N5 to mammals in both Europe and Canada, including seals in the UK, domestic cats in Iceland, and raccoons (and other small mammals) in Canada.

Last summer, in Cell Reports: Multiple Transatlantic Incursions of HPAI clade 2.3.4.4b A(H5N5) Virus into North America and Spillover to Mammals, researchers reported finding the mammalian adaptive E627K mutation in a number of samples.

While HPAI H5N5 doesn't currently appear likely to overtake or supplant H5N1, we've seen several abrupt dominant subtype changes (H1N1-> H5N8 -> H5N1) occur over the past 20 years.

With influenza, the only constant is change. 

All of which brings us to the following (translated) report, published yesterday by the Norwegian Veterinary Institute, which reports on H5N5 infections in Arctic foxes on Svalbard. 

Avian influenza detected in arctic foxes in Svalbard
Published 04.08.2025

The Norwegian Veterinary Institute has detected highly pathogenic avian influenza virus in four arctic fox pups from an area near the Russian settlement of Barentsburg on Svalbard. This is the first time the virus has been detected in arctic foxes in Norway.


Arctic foxes from Svalbard have been studied at the Norwegian Veterinary Institute. Photo: Ingunn Ruud, Norwegian Veterinary Institute

At the end of July 2025, the Governor of Svalbard received a report of several sick mountain foxes near the Russian settlement of Barentsburg. Three sick pups were initially observed, and two of these were euthanized for animal welfare reasons. Due to the proximity to Barentsburg and increased rabies vigilance, the rest of the litter was euthanized. Of the three remaining pups, one was sick. In addition, three adult mountain foxes near the den were euthanized.

H5N5 is circulating in the highlands

The arctic foxes were sent to the Veterinary Institute in Ås for testing for rabies and avian influenza viruses. The analyses showed that all the foxes were negative for rabies virus, while four arctic fox pups were positive for highly pathogenic avian influenza virus. The virus detected is of the subtype H5N5, a subtype that circulates in the high north and has caused cases of disease in both wild birds and mammals in the Nordic countries, Iceland and the United Kingdom in recent years. The subtype was detected in a walrus in Svalbard in 2023.

On the mainland, the H5N5 subtype has been detected in Nordland and Finnmark in June and July, with the last case being in a black-backed deer in Vadsø at the end of July. There have been no detections of H5N5 in mammals in Norway this year, but the subtype was detected in otters in Tromsø in October and December 2024, and in red foxes in Kvænangen in February 2024.

Infection pressure when eating infected birds

Arctic foxes can become infected with avian influenza through direct contact with sick or dead animals. Foxes are scavengers that are exposed to high infection pressure when they eat infected birds. Studies of red foxes on the mainland indicate that foxes do not have the ability to infect each other. Whole-genome sequencing of the viruses from arctic fox pups will be carried out to investigate whether there are signs of mammalian adaptation in the viruses.

May resemble rabies infection

Highly pathogenic avian influenza virus can cause clinical signs of brain disease and are similar to those seen in rabies infection. Neurological signs such as circling gait, tilted head position, paralysis and decreased shyness towards humans are common. Both highly pathogenic avian influenza and rabies are serious diseases that can infect humans, and it is therefore important to avoid contact with sick animals. If the population of Svalbard observes sick animals with or without neurological symptoms, it is important that the findings are reported to the Governor.

Report any suspicions to the Norwegian Food Safety Authority

If there is suspicion of infection with avian influenza in birds and other animals, the Norwegian Food Safety Authority must be notified . The Veterinary Institute is the national reference laboratory for avian influenza and has PCR diagnostics and whole genome sequencing available for the detection and characterization of avian influenza viruses.

Privately practicing veterinarians: Avian influenza in mammals | Norwegian Food Safety Authority

Although HPAI H5 is primarily regarded as a respiratory virus, two years ago (see Cell: The Neuropathogenesis of HPAI H5Nx Viruses in Mammalian Species Including Humans) researchers warned that ` . . . highly pathogenic avian influenza (HPAI) H5Nx viruses can cause neurological complications in many mammalian species, including humans'.

While clinical details on cases are often limited, we've already seen a small number of human infections reported as presenting with severe neurological involvement, including:

Vietnam: Ho Chi Minh DOH Reports A Rare H5N1 Encephalitis Case In a Child

Clinical Features of the First Critical Case of Acute Encephalitis Caused by Avian Influenza A (H5N6) Virus

CJ ID & MM: Case Study Of A Neurotropic H5N1 Infection - Canada

A sobering reminder that the next global health crisis may not play out like the last one, or the ones that came before.  As epidemiologists like to say:

“If you’ve seen one pandemic . . . you’ve seen one pandemic.”

PNAS: Three things we can do now to reduce the risk of avian influenza spillovers

 

#18,824

Perhaps the most unsettling thing about the rapid spread of HPAI H5 in the United States - and around the world - is how little is actually being done to try to prevent it from becoming the next pandemic.

Many countries appear willing to spend hundreds of millions of dollars on purchasing vaccines (which may - or may not - prove effective), but at the same time they make the testing of livestock largely voluntary, and are slow to share outbreak information. 

Last March - in Nature: Lengthy Delays in H5N1 Genome Submissions to GISAID - we learned that the average delay for countries to submit non-human sequences to GISAID is 7 months, and that Canada came in last at 20 months.

Despite the loss of tens of millions of lives and trillions of dollars during the COVID pandemic we seem unwilling to commit adequate resources to try to prevent the next global health crisis.  

Instead, we either deny the potential threat even exists, or we shrug our shoulders and say `nothing can be done'.  Either way, historians a hundred years from now are going to have a field day debating what kind of mass delusion paved the way to our failure to act. 

If a picture paints a thousand words - the following map, showing how many states have bothered to report HPAI in mammalian wildlife speaks volumes. 

New Mexico has reported 90 cases, Colorado has reported 74, California has reported 49, Washington 48 , New York 39, and Michigan 34  - while Arkansas, Tennessee, Alabama, Mississippi, Georgia, South Carolina, and West Virginia have reported none.  

Remarkably, more than half of all reported cases (n=643) in the United States since 2022 have come from just 6 states. Many states have only reported a small handful. 

Admittedly, most of the public seem to think avian flu is either a hoax, `a planned event', or simply overblown (see Two Surveys (UK & U.S.) Illustrating The Public's Lack of Concern Over Avian Flu), all of which highlights the persuasive power of social media.  

But even if HPAI H5 fizzles, there will be another emerging pathogenic threat to take its place.  Nature is nothing, if not persistent. 

Preventative steps, such as outlined in the following paper, should help reduce the risks from HPAI, along with a wide variety of other zoonotic threats; assuming we can be bothered to implement them. 

I've only posted the abstract and some excerpts, so follow the link to read it in its entirety.  

I'll have a brief postscript after the break.

Three things we can do now to reduce the risk of avian influenza spillovers

Kenneth B. Yeh kyeh@mriglobal.org, William P. Bahnfleth, Elaine Bradforda, +7 , and Matthew Scotch
https://orcid.org/0000-0001-5100-9724
July 30, 2025 122 (31) e2503565122
https://doi.org/10.1073/pnas.2503565122

Concern grows daily over the spread of highly pathogenic avian influenza (HPAI) across the globe. We call for three measures to radically lower the risk of a new influenza pandemic: (i) improved wildlife, agricultural, and human sampling for One Health surveillance; (ii) accelerated implementation of new indoor air engineering standards (American Society of Heating, Ventilating, and Air-conditioning Engineers [ASHRAE] Standard 241) and associated research on agent fate to significantly lower the potential for human respiratory infection; and (iii) continued investments in animal and human vaccines, along with improved public health communication that address the mechanisms of health disinformation campaigns. Given the stakes, it’s imperative that we act quickly.

An avian influenza pandemic remains within the realm of possibility. To reduce the risk, we need to engage in a One Health approach that includes wildlife, agricultural, and human sampling; implement new indoor air engineering standards; and invest more in animal and human vaccines, while improving public health communication to elucidate the mechanisms of health disinformation campaigns.  

        (SNIP)

In an era during which misinformation and disinformation in health communication is a reality, understanding its origins and impact on pandemic prevention, preparedness, and response is critical for pandemic preparedness. AI technologies for tracking and detection of misinformation and disinformation are already being used by governments and have the potential to improve early detection and response to these threats. Tailored public health messaging for health promotion can be proactive and effective when informed by active tracking and detection of fake news.

In summary, a broader research agenda should address these three additional critical areas for managing spillover and preventing a pandemic influenza—environmental surveillance, research and development in bioaerosols, and the enlisting of social and political scientists and new AI methods to better understand and respond to the infodemic around pandemics. While vaccines and other biomedical countermeasures are important, they are just part of the remedy.

Funding for pandemic preparedness should remain a priority. Improving early detection and response within agricultural settings will depend on better financial and policy incentives to help the farmers who are at the frontline and bear much of the risk. We need earlier, faster, and more efficient real-time pathogen surveillance and high-throughput sequencing in order to reduce risks to food security, minimize economic disruption, and limit the potential for high human mortality from agricultural-origin spillovers.

Broad monitoring of infected individuals and animals, development of mitigation strategies, development of community-targeted communication strategies, and adequate support for farmers across North America through a One Health approach would help control the virus before it gives rise to a pandemic. The One Health approach further builds resilience in the system since we require an integrated approach which reduces the shedding of virus by wildlife, the transmission to the bridging host, amplification and reassortment in the bridging host, and then infection of the human population. A series of environmental, ecological, veterinary, human, and built environment countermeasures is required to achieve this.

It is not too late to manage spillover events and keep one step ahead of HPAI. But public health officials and researchers must make this a priority—and soon.

       (Continue . .  )

While there is nothing radical, unique, or unreasonable in these suggestions - prevention has always been a much harder sell than preparedness. At least with preparedness, officials can point to stockpiled vaccines, PPEs, or body bags, as lifesaving assets.  

But with prevention - even if you manage to forestall the next pandemic by one, two, or even five years - eventually one will beat our defenses and the public will label prevention as a failure. 

So, while I consider these to be essential and reasonable suggestions, there doesn't seem to be much political will to implement them.

Hopefully that will change.

But if not, papers like this will still be valuable to those who will have to prepare for the inevitable pandemic-after-next.