Avian Flu Watch: Global H5N1 Tracker

Avian Flu Watch: Global H5N1 Tracker

Welcome to Avian Flu Watch, your data-driven update monitoring the worldwide spread of H5N1 bird flu as of September 2025. Let’s examine the epidemic’s hotspots, visualize current trends, investigate cross-border transmission, analyze containment successes and failures, spotlight emerging variants, and outline what travelers need to know right now.

Globally, the H5N1 crisis remains volatile, with human cases spreading across continents, driven by outbreaks in wild birds, poultry, and livestock. According to the U.S. Centers for Disease Control and Prevention, between January 1 and August 4, 2025, twenty-six human H5N1 infections were detected worldwide, eleven of which were fatal. Cambodia remains the most impacted: fourteen reported infections and eight deaths, primarily in provinces like Siem Reap, Prey Veng, and Kampong Cham. India has recorded two deaths and Mexico one fatality, all linked to direct poultry exposure. The United States last reported three cases, with no new detections since mid-February. Europe’s hotspots include isolated human infections, notably in the United Kingdom, where occupational exposure was the primary route.

The current global map paints Asia as the epicenter. Cambodia’s recent surge stands out: within seven months, eleven confirmed cases and six deaths, with age groups spreading from toddlers to older adults, all involving sick backyard poultry. India’s April fatality underlines risks in rural farming communities. In North America, Mexico’s tragic case in a three-year-old marks the virus’s deepening reach. In the U.S., containment efforts have shifted the 2024 burden westward—a mathematical model published in Nature shows the majority of U.S. livestock cases now concentrating in West Coast states, with interstate cattle export testing critical to reducing viral spread.

Visualizing the epidemic from 1997 to 2025, the WHO’s cumulative curve reveals sporadic peaks, with sharper rises since late 2021 as the genetically distinct clade 2.3.4.4b emerged. Overlaying hotspot data, Southeast Asia’s recent spike is most acute, but all continents—except Australia—have reported outbreaks. Trend lines indicate episodic surges corresponding to migratory bird movements and seasonal farming cycles; for example, clustered human cases in Cambodia coincided with local poultry die-offs during the wet season.

Cross-border transmission remains a major challenge. Phylogenetic analyses from the Middle East highlight how Turkey and Lebanon serve as pivotal regional nodes linking outbreaks in Egypt, Israel, and Gaza, with genetic sequencing confirming frequent reassortment among poultry, sometimes leading to host-switching events. Migratory birds facilitate transcontinental viral movement, while trade in live animals and poor biosecurity breach national containment lines.

Notable containment successes include the U.S. rapid testing and culling response, which helped avert broader human transmission

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This is Avian Flu Watch: Global H5N1 Tracker. Today, we dive into data from around the globe to monitor the spread and evolution of highly pathogenic avian influenza, subtype H5N1.

Let’s begin with the **geographic hotspots** and case counts. According to the CDC, between January 1 and August 4, 2025, 26 human infections with H5N1 were reported globally, resulting in 11 fatalities. Cambodia leads with 14 cases and eight deaths, often linked to direct contact with infected poultry. India has seen two deaths, while Mexico reported its first human fatality. In the United States, three cases surfaced in early 2025 but no further cases have been recorded since mid-February.

In the Americas, the Pan American Health Organization records 4,948 animal outbreaks since 2022 across 19 countries, notably the US, Mexico, and Brazil. A significant domestic event: in late 2024, 20 million chickens in the US were culled after outbreaks, creating shortages in egg supply. Data from the European region shows isolated human cases in the UK, including an unusual report of the virus found in sheep. The Middle East remains a genetic crossroads according to current phylogenetic analyses, with Turkey and Lebanon’s poultry strains closely tied to those in Israel and Egypt, underscoring cross-border transmission risk.

Now, imagine our trend lines: From a massive peak in the Americas late last year, cases plateaued but remain high, with sporadic spikes in Southeast Asia and South Asia. Comparative statistics show a nearly 50% case fatality rate for human H5N1 infections worldwide, underlining its severity. In the United States, trend data depicts a dramatic decline in human cases after targeted interventions, while poultry outbreaks continue at a steady pace especially in states such as Pennsylvania and Ohio.

Cross-border transmission patterns reveal viral flow via migratory bird flyways and interregional livestock trading. Poultry genetic analyses from Middle Eastern countries demonstrate common evolutionary branches, supporting observations of recent cross-border introductions. In the Americas, livestock transport models indicate moderate export-related transmission probability, with risk mitigated by testing and movement restrictions.

Turning to **containment**, the US federal order to test and restrict cattle movement significantly blunted the epidemic trajectory, proving effective compared to scenarios modeled without restrictions. In Southeast Asia, containment efforts have struggled, with ongoing outbreaks linked to dense live bird markets and limited biosecurity.

Emerging variants of concern include expanded reports of H5N1 in mammals—sheep and dairy cattle—as well as continued evolution in wild bird reservoirs. Genetic sequencing highlights the clade 2.3.4.4b subvariant, notable for cross-species jumps and limited adaptation to humans, though sustained human-to-human transmission is not yet documented.

Travel advisories recommend avoiding live animal markets

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This is Avian Flu Watch: Global H5N1 Tracker. Today is August 30, 2025.

So far in 2025, H5N1 avian influenza continues to impact animal and human health globally. According to the CDC, between January and early August, there have been 26 reported human H5N1 cases worldwide, with 11 deaths. Cambodia leads with 8 fatalities, followed by India with 2 and Mexico with 1. All infections involved direct contact with infected poultry or wild birds. No human-to-human transmission has been identified, and the immediate risk to the general public remains low.

Let’s break down the latest geographic hotspots. In the United States, only three human infections were reported in early 2025, with no new cases since February. Meanwhile, the United Kingdom’s Department for Environment reports 69 H5N1 outbreaks in England’s poultry sector this year, plus scattered cases in Scotland, Wales, and Northern Ireland. Across Asia, the WHO highlights continuing cases in India and reports of extensive animal outbreaks from China’s east coast, correlating with migratory bird flyways that connect across Northeast Asia and into Southeast Asia. A joint FAO-WHO-OIE assessment notes outbreaks spanning Africa, Europe, the Americas, and, for the first time, even Antarctica’s mainland in February.

The overall trend lines show continuing low-level, sporadic human infections, but high intensity in poultry and wild bird populations. The CDC’s global chart of H5N1 human infections over time remains relatively flat for 2025, following a spike in animal cases during the previous year. Modelling from Nature Communications indicates that in U.S. livestock, strict interstate testing for cattle, implemented after outbreaks in 2024, sharply curbed new cases and altered epidemic trajectories, showing a meaningful containment success.

Comparative statistics tell us the case fatality rate in humans is around 50% according to the latest WHO estimates, but occupational or environmental exposures remain the primary risk factors. Regions with intensive poultry farming and live animal markets, such as parts of China and Southeast Asia, are at persistent risk, especially along major migratory bird routes.

Cross-border spread remains a pressing concern. Genetic analysis of the 2.3.4.4b clade, now dominant worldwide, shows that migratory birds are a principal vector, with China a critical node linking outbreaks in East Asia, Southeast Asia, and beyond. Genetic divergence has arisen between cattle-origin H5N1 in North America and bird-origin strains in Asia, yet the potential for reassortment—the mixing of viral genes—poses ongoing risks.

Internationally, the U.K.’s recent regain of disease-free status for Northern Ireland stands out as a containment achievement, while the detection of H5N1 on Antarctica’s mainland in 2024 was an unprecedented warning about the virus’s global reach. Conversely, persistent outbreaks in Africa and Southeast Asia highlight where surveillance, biosecurity, and outbreak re

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This is Avian Flu Watch: Global H5N1 Tracker, your data-focused roundup monitoring the worldwide spread of bird flu—brought to you by Quiet Please.

As of late August 2025, H5N1 avian influenza remains a critical global health concern, with hotspots now concentrated in Europe and the Americas, a dramatic shift from Southeast Asia’s dominance in the 1990s. Machine learning-based geospatial analyses published in GeoHealth highlight expanding outbreaks from migratory bird pathways, transiting continents and linking distant habitats. Europe and North America are the largest epicenters, with tens of millions of birds lost and hundreds of millions culled in efforts to halt transmission.

The United States currently faces unprecedented challenges. All 50 states report H5N1 activity in poultry and wild birds, and—with H5N1 now detected in over 1,000 U.S. dairy herds and at least 3 confirmed human cases in 2025—the virus has crossed into new mammalian hosts, indicating increased pandemic risk. According to the Global Virus Network and CDC, over 168 million poultry have been euthanized across North America since 2022, and human infections include one recent fatality.

Current case data place Cambodia as Southeast Asia’s human case hotspot, with 14 recent infections and eight deaths so far in 2025, according to the CDC. India has reported two fatal H5N1 cases this year, with local poultry outbreaks fueling risk. Additional infections have been confirmed in Bangladesh, China, the United Kingdom, and the United States.

Visualizing trend lines, North America’s infection curve remains steep, driven by outbreaks in both livestock and poultry. By contrast, Asia’s trend is volatile but concentrated, often limited to communities close to poultry production. Europe shows persistent rolling waves, with surges in spring and fall tied to migratory seasons.

Comparative statistics reveal the U.S. dairy sector as a new front: nearly 950 herds in 16 states affected as of December 2024, and the emergence of two new H5N1 variants—B3.13 and the recently identified D1.1 in Nevada cattle. D1.1 underscores the virus’s ability to mutate and spill over independently, as noted by ongoing CDC surveillance.

Cross-border transmission patterns are shaped by bird migration, livestock commerce, and human movement. Open borders between U.S. states accelerated spread until federal orders mandated animal testing for interstate dairy transport. Modeling work in Nature Communications connects reduced interstate shipments and early intervention to slower epidemic acceleration in key hotspots, especially on the U.S. West Coast.

On containment, mass poultry culls and strict biosecurity in the U.K. and France have blunted some outbreaks, with rapid reporting and farm quarantines cited as key factors. Meanwhile, gaps persist: incomplete surveillance in rural Asia and limited compensation for farmers undermine early reporting, and slow restrictions on animal movement foster further outbreaks.

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Avian Flu Watch: Global H5N1 Tracker

Welcome to Avian Flu Watch, where we bring you the latest data and analysis on the worldwide spread of H5N1, also known as bird flu. Today is August 27, 2025.

Let’s start with the **numbers**. According to the U.S. Centers for Disease Control and Prevention, between January and early August 2025, there have been 26 confirmed human H5N1 infections globally. Of these, 23 were reported outside the U.S., leading to 11 deaths. Cambodia leads with 8 fatalities, followed by India with 2, and Mexico with 1. The U.S. has not reported any new human cases since mid-February, but nearly 1,000 dairy cow herds and more than 70 people were affected over the last year, with at least one U.S. fatality, as per The Lancet’s commentary.

Hotspots are shifting. Right now, **Southeast Asia remains the epicenter**, especially Cambodia and neighboring regions with intensive poultry farming and live bird markets. In the Americas, sporadic outbreaks continue in Mexico, the U.S., and Central America. The Pan American Health Organization lists almost 1,000 global human cases and a historical case fatality rate close to 50 percent.

When visualizing the epidemic trend line, you’d see **sharp spikes** in Southeast Asia and a steep rise between 2022 and 2025 in the Americas, followed by stabilization in the U.S. since spring this year. Outbreaks in dairy cattle since 2024 have noticeably altered the shape and scale of the U.S. trend, prompting a recalibration of surveillance systems.

Globally, **cross-border transmission** is increasingly tied to animal movement and migratory bird flyways. Recent mathematical models, as published in Nature Communications, estimate that U.S. West Coast states carry the highest probability of exporting infected cattle. Interstate and international cattle testing protocols, as well as restrictions, have contained spillovers compared to a scenario without controls, but risk persists where coordination is weak.

There are both containment successes and failures. The U.S. response, involving rapid diagnostics and targeted trade restrictions, helped halt widespread human transmission after the initial dairy cow outbreaks. In contrast, delays and inconsistent biosecurity in parts of South and Southeast Asia have led to recurring human infections linked to close contact with poultry or livestock.

Variant evolution is a key worry. Most recent animal and human cases globally have been attributed to the **B3.13 clade**—responsible for the bulk of U.S. dairy and human infections—but this year’s emergence of the **D1.1 lineage** in Nevada cattle signals ongoing viral adaptation. Experts stress the risks that these new variants present, especially their potential for crossing into new species.

As for travel, authorities recommend heightened caution in Southeast Asia, particularly rural Cambodia and other high-incidence regions. Travelers are advised to avoid markets selling live birds and dairy products that are unpa

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Welcome to Avian Flu Watch: Global H5N1 Tracker, your weekly source for data and analysis on the worldwide spread of highly pathogenic avian influenza. I’m your host, and over the next three minutes, we’ll break down the latest numbers, map out hotspots, track the virus’s evolution, and help you stay informed.

As of August 2025, avian influenza A(H5N1) continues to surge globally among both animals and people, with the virus showing a dangerous capacity to jump species. The World Health Organization reports nearly one thousand laboratory-confirmed human infections since 2003, spanning 25 countries, and in 2025 alone, Cambodia has seen 14 cases with eight deaths. Globally, between January and August, 26 human cases were detected in seven countries outside the U.S., 11 were fatal, mainly in Cambodia, India, and Mexico. All recent human infections involved contact with infected poultry or wild birds. Fortunately, there is still no evidence of sustained person-to-person transmission, but authorities warn that the risk of a pandemic remains[WHO][CDC].

Looking at geographies, the most acute human outbreaks this year are in Southeast Asia. Cambodia’s Siem Reap, Takeo, and Prey Veng provinces account for most fatalities, with the majority of cases traced to backyard poultry exposures. In India and Mexico, isolated deaths highlight the virus’s continued threat. In the United States, the situation has shifted since early 2024, when over 70 human cases were reported. Since mid-February, however, new human cases have ceased, underscoring the success of containment strategies.

Among animals, the spread has intensified, notably in U.S. dairy cattle. CDC data reveal all 50 U.S. states have H5N1 detections among birds, and by December 2024, about 950 cattle herds across 16 states were affected. Mathematical models published in Nature predict the disease burden is highest along the U.S. West Coast, with rigorous interstate testing helping limit viral spread. This model simulates the probability of exported cattle testing positive and emphasizes the benefits of early, strong detection measures.

Visualizing trend lines, we see global human case numbers remain low compared to animal infections, but the fatality rate is high, exceeding 40% in current outbreaks. Animal infections, especially in livestock, are on a sharp upward trajectory, reflecting the virus’s expanding host range. Hotspots map out sharply on Southeast Asia and Western U.S., with recent clusters in Cambodia signaling persistent risk.

Phylogenetic analysis of H5N1 strains detected this year shows cross-border transmission—Turkey and Lebanon play pivotal roles in moving the virus regionally, while genetic links tie Egypt and Israel outbreaks together. The emergence of new variants is a growing concern. Notably, the D1.1 variant appeared in Nevada dairy cattle, characterized by independent spillovers from birds to cows, diverging from the dominant B3.13 lineage. These changes raise the stakes for o

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This is Avian Flu Watch: Global H5N1 Tracker. Today’s data tells a vivid story of a virus evolving on a global scale, prompting vigilant public health responses and critical scrutiny. Let’s dive into the latest numbers, trend lines, travel advisories, and genetic developments shaping the H5N1 emergency in August 2025.

First, the headline figures. According to the CDC, there have been 26 confirmed human H5N1 cases worldwide since January, resulting in 11 deaths. Cambodia stands as the current hotspot, reporting 11 cases and 8 deaths, according to WHO and CDC summaries. These cases are spread through several Cambodian provinces, with Siem Reap, Takeo, and Kampong Cham at the center of recent outbreaks. Notably, all Cambodian cases involved direct exposure to sick poultry, mainly backyard birds, and affected all age groups, though men comprised 63 percent of infections. The US recorded three human cases earlier in the year, all linked to dairy cattle contact; no additional US cases have emerged since February.

Beyond Cambodia, fatalities have occurred in India and Mexico. India recorded two deaths, both tied to high-exposure poultry environments. Mexico reported one death in a rural farming region, with local authorities rapidly implementing containment protocols.

Visualizing the outbreak, trend lines are sharply up in Southeast Asia, with Cambodia’s June surge dominating the regional case distribution. North America shows a plateau since late winter, reflecting successful herd containment efforts and restrictions on interstate dairy cattle movement. Past data saw over 950 affected herds across 16 US states, but aggressive testing, export restrictions, and sanitation guidelines have flattened the curve by mid-2025.

Comparative statistics illustrate clear contrasts. Cambodia’s case fatality rate approaches 54 percent, starkly above the global 42 percent average for 2025. US cases are lower in number and severity thanks to rapid containment. The spread in the Americas and Asia remains almost entirely linked to direct animal contact, with no evidence of sustained human-to-human transmission this year.

Cross-border transmission patterns tell a complex phylogenetic story. Genetic studies published in May traced clusters through Turkey, Lebanon, Egypt, and Israel, revealing similar viral lineages swapped between poultry populations, especially in regions with porous borders and frequent livestock trade. These findings underscore the need for transnational cooperation and synchronized surveillance systems.

Containment successes highlight the US and Europe, where mandatory cattle testing, early federal orders, and improved biosecurity in dairies dramatically reduced herd outbreaks. Failures, meanwhile, are apparent in Southeast Asia’s backyard poultry networks, which remain under-regulated and present ongoing risk. Vaccination campaigns in Mexico and India have slowed community spread, but sporadic surveillance gaps let some infections slip through.

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This is Avian Flu Watch: Global H5N1 Tracker. Today, we’re giving you a scientific snapshot of the worldwide bird flu landscape, focused on H5N1’s evolving reach, recent case numbers, transmission dynamics, global containment efforts, and critical travel advisories.

As of August 2025, the CDC confirms 26 human H5N1 cases globally since January, with 11 deaths. Cambodia is a current hotspot, reporting 11 human cases this year across eight provinces, including Siem Reap and Takeo. Cambodia’s cumulative figures since 2023 are 27 laboratory-confirmed human cases and 12 fatalities, illustrating a high case fatality rate, especially among individuals handling sick poultry in rural areas. India and Mexico each saw fatal infections earlier this year, but no human cases have been reported recently in the United States. Globally, human cases remain sporadic—strongly associated with direct contact with infected birds or mammals.

Visualizing transmission trends, recent outbreaks show upticks in Southeast Asia, particularly Cambodia, where seven cases occurred in June. Trend lines highlight clusters in rural provinces—Siem Reap saw four new cases in July alone. In the U.S., the distribution of animal outbreaks, especially among dairy cattle, is concentrated in West Coast states as of January 2025. According to mathematical models published in Nature Communications, California and nearby states faced the highest probabilities of H5N1-positive animal exports, indicating areas of sustained viral activity.

Comparing regions, Southeast Asia reports the most human infections, while North America, Europe, and the Middle East predominantly register animal outbreaks. As of January, the CDC notes all 50 U.S. states have detected H5N1 in animals, and about 950 dairy cattle herds in 16 states have been impacted. A new variant, D1.1, emerged in Nevada dairy cattle this February. Its appearance indicates repeated spillover events from birds to mammals, expanding the virus’s genetic diversity and posing new uncertainties for transmission and control. The B3.13 clade remains widespread among U.S. dairy cattle.

Cross-border patterns show regional spread in the Middle East as well. Phylogenetic analysis published in May 2025 demonstrates genetic links between H5N1 isolates in Turkey, Lebanon, Egypt, and Israel, confirming transmission pathways among poultry populations and occasional host switching. Ecological overlap and animal trade remain key factors in movement across borders.

Major containment successes include the absence of recent U.S. human cases, attributed to strong federal controls on cattle movement and vigorous testing requirements for interstate exports, especially in West Coast states. The FDA’s guidelines on milk pasteurization have been central to risk reduction in dairy systems. Conversely, containment failures are visible in Cambodia, where low vaccination coverage and incomplete surveillance allow rural poultry outbreaks to seed sporadic human cases.

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Welcome to Avian Flu Watch Global H5N1 Tracker a data-driven update on the worldwide spread of bird flu as of August 2025

Let’s start with a snapshot of recent H5N1 activity By August 4th the CDC reports 26 confirmed human infections of H5N1 globally since January 2025 with 14 in Cambodia including eight deaths India has reported two fatal cases and Mexico one All reported cases were linked to direct contact with poultry or wild birds Critically there’s no verified evidence of sustained person-to-person transmission at this time but health authorities stress continued vigilance in both human and animal populations

Cambodia now stands as the global hotspot This surge has been widely noted by international health agencies with the majority of recent cases and fatalities occurring there As a trend the Southeast Asia region continues to be highly affected but the H5N1 threat remains present across Asia Europe North America and Africa though with regional variation In India recent cases have clustered near border poultry farms heightening concern for cross-border viral movement Mexico’s case was similarly near animal trade routes

In the United States no new human cases have been reported since mid-February but experts remain cautious due to previous outbreaks in both people and animals During 2024 and early 2025 over 70 human cases were documented in the US many linked to the first-ever large-scale spillovers to dairy cattle According to Nature the majority of animal cases in early 2025 were clustered along the West Coast with mathematical models projecting a higher likelihood of positive livestock exports from these states throughout the year

Visualizing these trends on a world map we see sharply rising case numbers in Cambodia highlighted as the epicenter while cases remain sporadic but recurrent in India and isolated in North America A corresponding trend line for 2025 would show a pronounced surge in Cambodia with a global background level punctuated by scattered outbreaks

Gene sequencing and phylogenetic analysis reveal significant cross-border viral exchanges in the Middle East Turkey Lebanon Egypt and Israel have all shared closely related strains over the past decade reflecting persistent cross-boundary transmission Regionally, genetic clusters confirm that animal and human cases in neighboring countries can often be traced to similar viral lineages shared by migratory birds and animal trade According to the CDC H5N1 infections now span not just birds but a growing number of mammals including cows highlighting the virus’s ability to adapt and occasionally jump species

International containment efforts have had mixed results Rigorous interstate testing and movement restrictions in the US appear to have limited large-scale interstate spread since spring 2025 By contrast lapses in farm biosafety and wildlife monitoring contributed to the surge in Cambodia and swift reappearance of H5N1 in Indian poultry markets Mexico’s timely identificatio

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This is Avian Flu Watch: Global H5N1 Tracker, your data-focused update on the worldwide spread of H5N1 bird flu.

Let’s begin with the geographic hotspots. According to the US Centers for Disease Control and Prevention, Cambodia has reported fourteen human H5N1 infections so far in 2025, resulting in eight deaths. Seven of these cases are children. The viral clade in Cambodia—2.3.2.1e—has been endemic in poultry for years, but continues to spill over to humans. India reported two fatal human cases—one child and one adult—earlier this year; both had links to poultry, but no human clusters have emerged there. In North America, the Global Virus Network and CDC confirm an escalating crisis: H5N1 is now present in all 50 US states, across Canada, and has spilled into over 1,000 American dairy herds since 2022, marking an unprecedented expansion into mammalian hosts.

Now let’s describe the trend lines. Visualize rising peaks on incident graphs throughout 2024 and 2025: the US shows the steepest climb, first in poultry, then cattle. Over 168 million poultry culled in the US and Canada underpin a relentless upward trend. Cambodia’s human case line remains low but persistent, with sharp local spikes. In India, the curve is flatter but worryingly creeping upward.

A look at comparative statistics: In 2025, the United States reports over 70 human H5N1 infections, with its first recorded death and vast animal losses. In contrast, Cambodia’s 14 cases this year account for more than 45 percent of its total reported human H5N1 cases over the past three years. Globally, since 2003, over 800 human H5N1 infections have been documented, with a case fatality rate exceeding 50 percent, reflecting ongoing lethality.

Turning to cross-border transmission, genomic analyses published in The Lancet and Nature highlight repeated viral movement across Eurasia and Africa. Turkey and Lebanon serve as regional hubs in the Middle East, where closely related viral genotypes have been identified in neighboring countries, revealing complex poultry trade and migratory bird connections. In the US, mathematical models from Nature Communications show that interstate cattle movement became a key risk after the virus entered dairy herds in 2024. Testing and cattle movement restrictions have curbed, but not stopped, spread.

Containment success stories include Cambodia’s rapid clinician outreach and targeted education. These efforts have capped human-to-human transmission so far. In the US, swift federal movement controls on cattle exports slowed viral jumps between states, though the scale of livestock outbreaks shows major gaps remain. By contrast, failures are evident in under-resourced countries where delayed outbreak recognition and weak biosecurity have allowed undetected viral circulation.

In terms of variants, 2025 brought a new H5N1 mutation in US cattle, dubbed D1.1, with genetic features suggesting recent avian-to-mammal adaptation. Its continued surveillance is critical, as

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