The US Department of Agriculture has verified that Oklahoma is now the 13th state in the country to identify bird flu in dairy cows, although the state has indicated that the infection occurred several months ago. This confirmation reveals that the outbreak was more extensive than initially believed by US authorities after the virus was first discovered in dairy cattle in late March. Since then, bird flu has been found in over 150 dairy herds across the nation, according to a report from Reuters. These cases are linked to a widespread outbreak of H5N1 bird flu that has been spreading globally in wild birds, infecting poultry and various species of mammals. Despite four dairy workers testing positive this year, the US centers for disease control and prevention has said that the risk to the general public remains low. According to Lee Benson, spokesperson for the Oklahoma department of agriculture, food and foresty, an Oklahoma dairy collected the positive sample in April when it suspected its herd may have been infected. The dairy recently sent stored samples to USDA for testing after learning it could receive financial assistance for lost milk production due to bird flu. USDA has initiated a program to compensate farmers with sick cows for 90% of lost milk production per cow to encourage farmers to test herds and report infections. USDA's website reports two positive herds in Oklahoma, but Benson clarified that the confirmed positive sample is from one Oklahoma dairy with two separate barns. The state's agriculture department believes USDA received the dairy's samples in the first week of July, and the herd has fully recovered. Oklahoma has not received reports of other possible infections. To address the situation, Oklahoma has provided protective gear to dairy farmers and requested dairies to enhance safety and security measures, according to state veterinarian Rod Hall. However, there is no mandatory testing of cows in Oklahoma, as per the state agriculture department. In related news, Colorado has reported four confirmed bird flu infections in poultry workers and is investigating a fifth suspected case, according to health authorities on Sunday.
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A new study offers valuable insights into tailoring immunization strategies to optimize influenza vaccine effectiveness.
To offer cross-protection against diverse influenza virus variants, nanoparticle vaccines can produce pivotal cellular and mucosal immune responses that enhance vaccine efficacy and broaden protection, according to the study in Nature Communications.
To alleviate the significant public health burden of influenza epidemics and occasional pandemics, its essential to enhance influenza vaccine cross-protection, researchers say.
While the Centers for Disease Control and Prevention (CDC) recommends annual influenza vaccination, current seasonal influenza vaccines typically provide strain-specific and short-lived immunity. Seasonal influenza vaccines offer limited cross-protection against antigenically diverse virus variants and provide no defense against sporadic influenza pandemics, the authors explain.
Developing effective influenza vaccines or vaccination strategies that can confer cross-protection against variant influenza viruses is a high priority to mitigate the public health consequences of influenza, says first author Chunhong Dong, a postdoctoral fellow in the Institute for Biomedical Sciences at Georgia State.
In the study, the researchers investigated the effects of immunization strategies on the generation of cross-protective immune responses in female mice using mRNA lipid nanoparticle (LNP) and protein-based polyethyleneimine-HA/CpG (PHC) nanoparticle vaccines targeting influenza hemagglutinin. The mice were immunized with either intramuscular mRNA LNP or intranasal PHC vaccines in a typical prime-plus-boost regimen. A variety of sequential immunization strategies were included in this study for comparison.
We demonstrated that cellular and mucosal immune responses are pivotal correlates of cross-protection against influenza, says Baozhong Wang, senior author of the study and a professor in the Institute for Biomedical Sciences.
Notably, intranasal PHC immunization outperforms its intramuscular counterpart in inducing mucosal immunity and conferring cross-protection. Sequential mRNA LNP prime and intranasal PHC boost demonstrated optimal cross-protection against antigenically drifted and shifted influenza strains.
The study highlights the importance of immunization orders and indicates that in a sequential immunization, an mRNA vaccine priming plays an important role in steering the Th1/Th2 immune responses. Also, the intranasal PHC boost is crucial to the induction of mucosal immunity, Wang says.
The National Institutes of Health/National Institute of Allergy and Infectious Diseases funded the work.
Source: Georgia State
In March of this year, federal agencies announced that highly pathogenic avian influenza, specifically type A (H5N1), had been identified in US dairy cattle for the first time. PC: Hawaii Department of Agriculture
State and federal agencies are keeping a close eye on H5N1,the influenza A strain associated with highly pathogenic avian influenza (HPAI) that has infected dairy cows in multiple states, as well as four people who worked closely with the infected cows.
Residents are reminded that it is safe to consume pasteurized milk or cheese, but raw milk can carry the live virus and should be avoided.
At present, Hawaii is the only state in which H5N1 has not been detected.
The Hawaii State Department of Health (DOH), in partnership with the state and federal Departments of Agriculture and the Centers for Disease Control and Prevention (CDC), is reinforcing long-standing efforts to detect avian influenza disease in birds, cattle, and humans in Hawaii. On the human health front, this includes monitoring human influenza infections detected in the laboratory, monitoring influenza in wastewater and tracking ED visits for influenza on theHawaii Respiratory Disease Activity Summarydashboard. Further information regarding H5N1 risks in Hawaii and prevention guidelines can be found on the updated DOHavian flu website.
In response to the detection of H5N1 in dairy cows on the mainland earlier this year, the Hawaii Department of Agriculture (HDOA) issued an advisory on April 5 to prevent the importation of cattle from premises where H5N1 has been detected, or presence was suspected and required that cattle from affected states be examined within 72 hours of shipment and to be found free of clinical signs of H5N1. Starting April 27, the US Department of Agriculture implemented a national restriction on movement of lactating cows, which requires testing of the animals for H5N1 be performed before any interstate movement.
H5N1 is typically carried and transmitted by birds. Surveillance testing is routinely performed on domestic and wild birds and incidentsof unusual morbidity and mortality are investigated to verify H5N1 is not present. HDOAs primary focus is on domestic poultry, while the US Geological Survey (USGS) and US Department of Agriculture Wildlife Services have enhanced focus on wild birds.
Wild bird surveillance: The Hawaii State Laboratory (HSL) receives and tests specimens collected by USGS from live wild birds. More than 100 test results since 2022 have been negative. DOH has requested that the USGS increase sampling, especially of migratory birds such as klea (Pacific Golden Plover) when they return in the fall.
Domestic poultry:Since 2022, HSL has conducted H5N1 tests on samples from hundreds of birds, including those provided by Oahus largest poultry farm as part of a routine monitoring program; birds from small or large farms in all counties that appear to be ill; and imported birds. All tests so far have been negative.
Cattle: Hawaii has one dairy farm, on Hawaii Island, that does not import cows from off-island. No dairy cows have been imported into Hawaii in the years since H5N1 was first detected in the US Imported livestock cattle are inspected by an HDOA veterinarian; none exhibited any signs of illness that would have triggered testing.
Human influenza subtype monitoring:HSL routinely conducts subtyping on specimens provided by commercial labs that were collected from people who tested positive for influenza throughout the state, by a method that is able to presumptively identify novel subtypes, including H5N1. HSL is also able to confirm H5N1 with a more specific test. HSL has subtyped more than 620 human specimens during the current flu season to date, with no detections of H5N1.
Wastewater surveillance: WastewaterSCAN,a CDC National Wastewater Surveillance System partner, is performing continuous H5N1-specific testing (by polymerase chain reaction) on wastewater from the Sand Island treatment plant as of several months ago and has reported no detections.
H5N1, known as bird flu, is becoming an increasing problem in the U.S. The virus normally only infects poultry and wild birds, but it's becoming more adept at infecting mammals; so far, it's infected cattle in 12 states. A small number of people are also falling illseveral dairy workers have been contracted mild illnesses and recovered.
The latest research published in Nature suggests that the current strain may be more adept at infecting mammals like cows. Researchers led by Yoshihiro Kawaoka, a professor at the University of WisconsinMadison and the University of Tokyo, report that the current version differs from previous H5N1 strains and has mutations that make it easier for the virus to infect mammalian cells. Kawaoka says that this ability is more than what we saw in the past with avian H5N1 viruses, but it is still limited.
The group tested virus obtained from infected cows in both mice and ferretsthe latter of which are a good model for how influenza viruses may act in people. Only one in four uninfected ferrets that were housed in the same cages as infected ones tested positive for H5N1. But how well a virus spreads depends a lot on how much virus is present, and at the moment H5N1 in dairy cattle does not appear to concentrate in the respiratory tissuesmeaning its not saturating airborne particles the animals may exhale and inhale. Instead, its primarily found in the mammary glands, and therefore in the milk the cows produce.
Read More: We Are Not Safe from Bird Flu Until We Protect Farmworkers
Thats a concern for dairy workers and anyone drinking raw, unpasteurized milk. We should be concerned because there is a huge amount of virus present in milk, says Kawaoka. The biosecurity in farms is limited, so there is a lot of virus out there, and its very important to contain this virus as soon as possible.
Kawaoka and his team recently quantified the amount of virus in the milk of an infected cow in a report published in the New England Journal of Medicine. They found a very high number of infectious particles in a single milliliter of raw cows milk. Pasteurization inactivated the virus, but Kawaoka says the effectiveness of the heat pasteurization depends on how long the milk is treated and how much virus is present.
If the virus doesnt spread easily among ferrets, how is it transmitting so readily among cows? Kawaoka says its not likely that cows are actually passing the virus among themselves. Instead, because H5N1 is so highly concentrated in the mammary glands and milk, its likely that the virus is spreading via contaminated milking machines that arent cleaned thoroughly between each milking.
The results are reassuring in the sense that for now, H5N1 doesnt seem to pass easily from animal to animal. But the fact that the virus is different from previous strains and has picked up the ability to more easily infect mammals is concerning, says Kawaoka. Health officials are closely monitoring samples from both infected cattle as well as the handful of dairy workers who have tested positive for H5N1 to ensure the virus isnt mutating further to spread easily among people. If it does, they say they are ready with three vaccines, currently in the vaccine stockpile, that can protect against severe infections.
Australia is experiencing 3 different outbreaks of highly pathogenic avian influenzas.
Dr Debbie Eagles, director of the Australian Centre for Disease Preparedness (ACDP) at CSIRO, describes this as unprecedented.
This year ACDP has conducted 3,000 tests on 1,000 samples since the first detection of H7N3 near Meredith in Victoria in May, and subsequently H7N9 Terang in Victoria, H7N8 in New South Wales and [Australian Capital Territory], says Eagles.
Presently, H7N3 has spread to 7 additional Victorian poultry farms, while H7N8has spread to 2 commercial poultry farms in NSW, and 1 in the ACT.
Previously when weve had outbreaks in Australia thats been a single strain, usually then affecting 1 region, says Eagles.
Prior to this year, there has only been 8 outbreaks of H7 highly pathogenic avian influenza (HPAI) in Australia since 1976.
Avian influenza viruses are described according to the combination of 2 groups of surface proteins: haemagglutinin or H proteins (H1 to H16) and neuraminidase or N proteins (N1 to N9).
Samples from each of the affected properties sent to ACDP for whole genome sequencing and bioinformatic analysis confirmed that the outbreaks are not linked.
Instead, the 3 strains are more closely related to H7 strains carried by local Australian wild bird populations, which Australia has a good baseline understanding of thanks to the National Avian Influenza Wild Bird (NAIWB) Surveillance Program.
Usually, these circulate in wild waterfowl, such as ducks and geese, as low pathogenic avian influenzas (LPAI), which do not cause signs of disease. However, when H5 and H7 strains get into commercial poultry farms, they have the potential to mutate and become highly pathogenic causing devastating disease and death in chickens.
This is basically due to a mutation of a single virus gene and were not saying that these mutations dont occur in wild birds as well, but the impact is much more significant in commercial chicken farms because of the nature of how birds are housed, says ACDP senior research scientist and World Organisation for Animal Health (WOAH) expert for avian influenza, Dr Frank Wong.
Wong says that in commercial chicken farms a lot more birds are located in close contact.
And chickens actually are naive host population for avian influenza viruses, so theyre more susceptible to infection because often they dont have inbuilt immunity. So, once a virus turns highly pathogenic, the attack rate is very rapid, it burns through the population, he says.
Why 3 separate strains have made the jump to poultry in just the past few months remains unknown.
There could be many reasons we dont really know because viruses [are] being carried in wild birds [and it] is very difficult to have a continuous picture of whats going on before they get into commercial chicken farms, says Wong.
So it could be many things, the wild bird dynamics at a particular point of time, climate, changes in weather patterns, or just coincidence.
So, while any new spillover events cannot be predicted before they occur, state authorities in VIC, NSW, and ACT are controlling the movements in already affected areas to minimise and prevent the risk of further spread of existing outbreaks.
Eagles says: Each of the infected properties has been dealt with by local authorities in terms of the necessary disposal and subsequent ongoing decontamination of those facilities. That is consistent with a response plan that all states and industry agreed to in advance. So, its a very well-developed response plan that Australia has.
And, while Australia currently doesnt vaccinate poultry against avian influenza, she says there are ongoing discussions around whether it might be used for certain high-risk species and for people in preparation for the HPAI H5N1 clade 2.3.4.4b H5N1.
Viral strains in this clade are circulating internationally causing severe disease in poultry, and species of wild birds and mammals including cattle (in the US) and marine mammals. It has reached every other continent through the movements of migratory waterfowl that do not come to Australia.
Indonesia and countries like the Philippines within our region already have this virus its been circulating in those countries, our near neighbours, for a couple of years, says Wong.
The risk there is more in our regional nomadic duck species what we call the bridging species, that might be affected and then kind of hop from island to island.
In response to the threat posed by a potential incursion of H5N1, last week the government announced $1.1 million of ongoing funding to extend the NAIWB Surveillance Program for 4 years.
The risk-based surveillance program focuses on sampling wild birds at locations near both human populations and commercial poultry farms. But, according to Wong, there are plans to expand and increase the efficiency of this surveillance in northern Australia.
Thats where we think would be the higher risk for an incursion of exotic strains of HPAI viruses, says Wong.
But again, the northern part of Australia ironically poses the most challenge in terms of logistics and coverage because theyre remote sites with very low population and a lot of distance to cover.
The US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) today added five more dairy herds in three states to its list of H5N1 avian flu outbreak confirmations.
Also, APHIS confirmed the virus in three more cats from two states, both of which are experiencing H5N1 outbreak in dairy cows and poultry.
Most of the APHIS confirmations involve detections initially announced by states. The newly added outbreaks include 3 in Colorado, 1 in Michigan, and 1 in Texas, boosting the USDA's total to 145 in 12 states.
Separately, the Minnesota Board of Animal Health reported another new outbreak in a dairy herd, which involves cows from Benton County in the central part of the state. Minnesota has now reported eight H5N1 outbreaks at dairy farms.
In related developments, APHIS confirmed H5N1 detections in three more domestic cats, two from Minnesota and one from Michigan, raising the total since 2022 to 33.
A notification from the World Organization for Animal Health (WOAH) said the cats from Minnesota were feral barn cats on an affected dairy farm in Sibley County in south central Minnesota. Samples were collected on June 10.
Meanwhile, APHIS said samples from the Michigan cat were collected on April 18 and that the cat was from Ottawa County, one of 10 Michigan counties affected by outbreaks in dairy cows. Also, APHIS reported an H5N1 detection in a raccoon from Ottawa County, with samples collected on the same date as the cat.
Additionally, APHIS reported four more H5N1 detections in wild birds from two Iowa counties, all agency-harvested birds that were sampled in mid to late June. The birds that tested positive were from Plymouth and Sioux counties and included a red-winged blackbird, robin, turkey vulture, and barn swallow.
Bird flu or avian influenza cases in humans are on the rise in the US sparking fear of another pandemic similar to Covid-19. Four dairy workers have tested positive for H5N1 strain in the country amid massive spread of the virus in dairy cows. While there have been no cases of human-to-human spread of the highly pathogenic avian influenza H5N1 so far, the pathogen could evolve to infect humans more efficiently. Bird flu cases in cows had been unheard of till this year's outbreak. The first known cases of infected dairy cattle were observed in Texas in March; it has now grown to dairy herds in 12 states. According to United States Department of Agriculture (USA), 151 dairy cow herds have confirmed cases of avian influenza A(H5N1) virus infections in dairy cows as the number of infected herds continues to grow. Since 2022, USDA APHIS has reported HPAI A(H5N1) virus detections in more than 200 mammals in the USA. Human cases of bird flu are so far spread from poultry, live poultry markets, or dairy cattle so far. Symptoms of human bird flu begin within two to eight days of infection and at start may seem like common flu. Cough, fever, sore throat, muscle aches, headache and shortness of breath are other symptoms. As the condition turns worse, gut issues, breathing issues, or CNS changes are reported. What is bird flu? Bird flu, or avian flu, is an infectious viral disease that spreads among birds. In rare cases, it can affect humans. H5N1, H7N9, H5N6 and H5N8 strains of the virus have been spreading in recent years. Bird flu can spread to humans if they touch the infected birds or their droppings or bedding. It may also spread while killing or preparing infected poultry for cooking. Human bird flu infection cases rising in the US "Bird flu is spreading in cattle herds in the US in a surprising development. Scientists term the route of transmission as 'artificial' which means the cows are not passing it to one another through natural contact and it probably isn't transmitting in airborne particles from cow-to-cow," says Dr R S Mishra, Principal Director - Internal Medicine, Fortis Escorts, Okhla Road, New Delhi. The expert says the transmission is happening in milking parlours and it looks like it's through contaminated milking machinery. Dr Mishra says the US spread of bird flu has been driven in large part by migratory waterfowl and the knowledge about migratory patterns and intercontinental associations of waterfowl, as well as genetic analyses of viral strains support the hypothesis that the recombinant highly pathogenic avian influenza (HPAI) H5N8 entered North America from Asia via migratory birds. "Colorado has reported four confirmed infections of H5N1 bird flu virus in poultry workers, and is checking on the status of a fifth suspected case. The workers showed mild symptoms, from conjunctivitis, or pink-eye, to respiratory signs. Human infections with H5N1 avian flu could cause severe disease and even a pandemic if the virus were to change and acquire the ability to spread easily between people hence it is of extreme importance to monitor its spread," says Dr Tushar Tayal, Consultant, Internal Medicine, CK Birla Hospital, Gurugram. Precautions to follow to prevent bird flu Dr Mishra lists the following preventive measures that must be taken to avoid getting infected by the virus. 1. Proper sanitary measures must be implemented to prevent bird flu. This includes application of foot bath at the entry of the farms, washing of utensils and equipment after use at the farms. 2. One must wash their hands properly before and after various poultry-related work. 3. Avoid close contact with infected or suspected birds and animals, especially their droppings, saliva and other secretions. 4. Avoid consuming raw/uncooked/partially cooked poultry products such as chickens and eggs. Cooking for half-an-hour and 700C kills the bird flu virus. Symptoms of bird flu Symptoms of bird flu in humans include fever and cough, sore throat, muscle aches, conjunctivitis (eye infections), severe respiratory illnesses such as pneumonia. Complications of bird flu include pneumonia, organ failure, and acute respiratory distress syndrome (ARDS). Is vaccine the answer? Vaccination plays a crucial role in curbing diseases in both cattle and humans, particularly in the context of avian influenza outbreaks. Vaccinating against avian influenza can reduce transmission rates. Researchers are actively developing and testing vaccines for cattle, with promising candidates using mRNA technology and harmless DNA viruses to deliver genetic material. For humans, vaccination can protect individuals from getting ill and mitigate the risk of avian influenza viruses mixing with seasonal flu strains. This could prevent virus from being evolved to a more transmissible and dangerous forms. Countries like Finland and the United States are already vaccinating high-risk workers and stockpiling doses, emphasising the importance of preparedness. Additionally, advanced mRNA-based vaccines offer a rapid and adaptable response to emerging strains, enhancing the ability to manage potential pandemics effectively.
Three poultry workers from a farm in northeast Colorado are suspected of contracting bird flu, state and federal health officials announced Friday.
Specimens have been sent to the CDC for confirmation. The workers who tested presumptive positive had mild symptoms and were helping with the depopulation of poultry at a facility dealing with an H5N1 outbreak.
The H5 bird flu is spreading among wild birds and causing outbreaks in dairy cows and poultry across multiple states. The CDC is sending a team to Colorado to assist with the ongoing investigation at the states request.
There have been four confirmed human cases of bird flu in the U.S. since March, all in farmworkers, with two in Michigan, one in Texas and one in Colorado, the CDC said.
In the latter case, a Northern Colorado farm worker developed pink eye after direct contact with cattle infected with avian flu, according to the CDPHE.
The U.S. Department of Agriculture has confirmed bird flu outbreaks in 152 cattle herds so far this year.
The CDC stated that the risk to the public from bird flu remains low, with no signs of unexpected increases in flu activity in Colorado or other states affected by H5 bird flu outbreaks in cows and poultry.
However, the CDC added that human infections with this novel influenza virus (and others) are concerning because of the potential to cause severe disease.
Federal officials are considering when to deploy 4.8 million doses of the bird flu vaccine. Last month, Finland announced it would offer shots to workers who might be exposed to the virus.
Related:Research affirms that pasteurized dairy is safe from avian flu
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In spring 2022, a handful of red foxes in Wisconsin were behaving oddly. Veterinary pathologist Betsy Elsmo learned that a local wildlife rehabilitation center was caring for foxes with neurological symptoms like seizures, tremors, uncoordinated movements and lethargy.
But tests for common pathogens like canine distemper virus and rabies that typically cause the symptoms came back negative. Then a red fox kit tested positive for influenza A. This group of viruses includes seasonal flus that cause respiratory disease in people and many other strains that commonly circulate among animals such as waterfowl and other birds.
I was surprised, says Elsmo, of the University of WisconsinMadison. And to be honest, at first I kind of wrote it off.
That is, until a veterinary technician at the rehab center sent Elsmo a study describing cases of avian influenza in red foxes in the Netherlands. Examinations of the Wisconsin kits tissues under the microscope revealed lesions in the brain, lung and heart that matched what had been seen in the Netherlands animals. And I thought, I think it is [bird flu], she recalls.
Additional testing confirmed the diagnosis in the kit and the other foxes, Elsmo and colleagues reported in the December 2023 Emerging Infectious Diseases. The animals had contracted a lethal strain of H5N1 avian influenza that emerged in late 2020 in Europe and has since spread around the world. At the time infections were discovered in the Wisconsin red foxes, bird flu was expanding its incursion into North America.
Since H5N1 arrived on North American shores in December 2021, it has infected animals as wide-ranging as polar bears, skunks, sea lions, bottlenosed dolphins and cows (SN: 7/8/24). And one unwelcome revelation of the ongoing outbreak is the viruss propensity to invade the brains of myriad mammals.
H5N1 is now known to infect more than 50 mammal species. Scientists had documented bird flu cases in only about a dozen species during previous outbreaks.
Theres nothing particularly special about this strain that allows it to plague so many species, research suggests. Rather, because the strain has spread so far and wide among birds both wild and domesticated there are simply more opportunities for mammals to be exposed, says virologist Emmie de Wit of the National Institutes of Healths Rocky Mountain Laboratories in Hamilton, Mont. (SN: 1/25/24). For some mammals, infected birds may be on the menu. For others, their water or food might be contaminated with virus-laden bird excrement.
Water-loving birds are exposed to influenza A viruses so often that most have some form of immunity that can protect them from a serious case of H5N1. If the birds do exhibit symptoms, they are usually mild and respiratory or gastrointestinal in nature. But other birds that dont get infected as frequently, such as eagles, vultures and pelicans, can become severely ill and die.
In mammals, bird flu typically causes respiratory symptoms such as congestion or shortness of breath. Neurological symptoms such as seizures or paralysis are among the most striking and common signs that the virus has reached the brain. And once it does, the infection is often fatal. In the ongoing H5N1 outbreak, such cases have been confirmed posthumously in house cats, raccoons, sea lions, dolphins and several other species (SN: 5/31/24).
From a bottlenosed dolphin in Florida to a polar bear in Alaska, many mammals across the United States have tested positive for avian influenza since 2022. Click on a colored dot to find out what species the virus was detected in and the county in which the animals were found. Zoom in for a closer look.
H5N1 and its close relatives have an easier path to the brain compared with other flu strains, de Wit says. And the virus is exceptionally good at making copies of itself inside a variety of cells, including nerve cells.
To break inside a cell, flu viruses exploit a protein called sialic acid on the cells surface. Bird cells and mammalian cells in the upper airway typically have different types of sialic acids, which means that bird flu viruses dont easily infect mammals and vice versa.
But studies have shown that parts of the human brain, for instance, are covered in birdlike sialic acid proteins. Many cells, including the nerve cells in the olfactory bulb which is important for sense of smell and links directly to the brain also have additional proteins that allow H5 viruses to replicate. Both of those traits mean that theres a direct entry route [to the brain] from your nose, de Wit says. So avian flu viruses may pose a bigger threat to the brain than, say, seasonal influenzas that mostly target cells in the nose, throat and lungs.
Since 2003, there have been 891 cases of H5N1 in people, about half of which were fatal according to the World Health Organization. In the current outbreak, 15 people have been infected with the strain hitting mammals hard. Four people had severe disease two developed pneumonia and at least one died.
Symptoms in people can vary from mild to severe, and some individuals infected with avian influenza viruses during previous outbreaks have developed neurological symptoms. Such cases are rare, the agency says, although how often the virus makes it to the brain is unclear.
How often the virus invades the brains of other mammals is also unknown. Most countries dont regularly test healthy-looking wildlife for viral infections, so such cases likely represent only the sickest individuals, Elsmo says. Its possible that some infected animals never develop severe disease and therefore escape the notice of people.
Avian influenza viruses can affect other parts of the body as well. When you break it out by species, it seems like the pattern of tissues that are most affected are little bit different, Elsmo says.
For instance, foxes and raccoons seem to have severe brain lesions as well as lesions in the heart and lungs. Striped skunks, meanwhile, tend to have few brain lesions, some of which are mild compared with red foxes. Instead, at least in Elsmos experience, H5N1 seems to target the skunk livers and organs in the lymphoid system, which protects against infection and removes waste from the body.
Some animals that have been killed by H5N1 weirdly had signs of infection only in the brain. Flus a respiratory virus, says Richard Webby, a virologist at St. Jude Childrens Research Hospital in Memphis, Tenn. So [the respiratory system is] where it should be before anywhere else.
The brain of a red fox in the Netherlands, for instance, was infected with H5N1 but not the animals lungs. Red foxes and mink in Canada similarly had mostly neurological disease. And bird flu didnt seem to touch the lungs of a bottlenosed dolphin found off the coast of Florida in 2022, despite the animal having virus-infected brain tissue, Webby and colleagues reported April 18 in Communications Biology.
Its possible that the dolphin had cleared the respiratory infection before it died, but the team found no evidence of pulmonary disease. Nor do dolphins have a sense of smell, which eliminates the possibility that the virus could reach the brain through the nose.
Exactly how the virus might sometimes sidestep respiratory tissues and hitch a ride directly to the brain is unclear. One possibility is that H5N1 already has that ability. Maybe it was more common, but we just never had the numbers [of mammalian infections necessary] to see it, Webby says.
Or perhaps when a mammal like a red fox or a dolphin takes a bite out of an infected bird, viral particles in the meat gain a direct path to the brain via nerves lining the mouth and digestive tract.
Virologist and veterinarian Vctor Neira thinks thats what may be happening in some sea lions in Chile. He and colleagues investigated an outbreak in the animals in 2023 along the coast of Chile, including two animals that the team necropsied. Although one animal didnt have neurological symptoms, the other had paralysis, disorientation, lack of coordination and tremors, the researchers reported in October 2023 in Veterinary Quarterly. The virus had infected multiple organs including the lungs, liver and kidneys, but the highest viral counts came from the brain.
Because H5N1 hasnt been infecting sea lions for very long, since just 2023, there is still a lot to learn about how the virus affects the animals, says Neira, of the University of Chile in Santiago.
Just how many mammal species are susceptible to infection is an open question. Usually, scientists study influenza virus in swine, mice, humans and birds, Neira says. Different wild animals, even several domestic animals, have not been studied with this virus.
Theres an urgency to finding out. Thats because every infection gives the virus an opportunity to adapt in ways that could allow it to spread more readily among mammals, de Wit says. Some research suggests that the virus may be spreading from marine mammal to marine mammal in parts of South America. But so far, infections in other animals are largely dead ends, with no spread to other individuals. The risk to people remains low, although workers on poultry and cattle farms who work closely with animals are at a higher risk than the general public.
Still, we cannot stop paying attention, de Wit says. The ongoing outbreak serves as a reminder that viruses are versatile foes.
Scientists are raising the alarm about US cases of H5N1 in cows as transmission to humans is easier. Here in Europe, steps are being taken to prepare.
A strain of bird flu that jumped to dairy cows and then farmworkers in the US this spring could become a global health risk but the extent of the threat is unknown and officials in Europe and elsewhere could be caught unprepared if it escalates.
The US cases are the latest upswell of a highly pathogenic avian influenza (H5N1) that has been circulating among migratory birds and mammals in recent years, mostly in Europe and the Americas.
Since March, the strain has cropped up in 145 cattle herds in 12 US states and infected four dairy workers, all of whom went on to recover from their illnesses.
There has been no evidence of human-to-human spread, which is a key marker of pandemic threat, while no human cases of the strain have been reported in Europe, and the European Centre for Disease Prevention and Control (ECDC) says the general public is at low risk of infection.
Even so, experts say there are enough warning signs that European countries should already be monitoring the virus and getting ready to respond quickly if that changes.
Waiting until the virus emerges among people on this side of the Atlantic would allow H5N1 to spread unchecked for long enough that it becomes difficult, if not impossible, to quash.
Things can change very fast, and it's difficult to put a precise timeline on it, because it depends on what the emergence process looks like, Colin Russell, an evolutionary biologist at Amsterdam University Medical Center and chair of the European Scientific Working Group on Influenza and Other Respiratory Viruses (ESWI), told Euronews Health.
If we don't know what we're missing, we could already have a problem on our hands, Russell said.
The US outbreak has scientists worried as its the first time H5N1 has been documented in cattle, making it far riskier that the virus will spread to humans, and because H5N1 has been lethal in the past.
Between 2003 and 2024, H5N1 caused 889 illnesses and 463 deaths in 23 countries, a fatality rate of 52 per cent, according to the World Health Organization (WHO).
While the US strain doesnt yet have the mutations that enable rapid spread between people, researchers said this week that the inflection point could be closer than previously thought, after they found signs of transmission between small animals in lab tests.
Its a little bit concerning, because it means that the virus does have more ability than typical highly pathogenic avian influenza viruses to spread by air from mammal to mammal, Thijs Kuiken, professor of comparative pathology at the Erasmus University Medical Centre, told Euronews Health.
His research focuses on avian flu and other emerging viral diseases but he was not involved with the recent study.
Kuiken and other experts say the risk from H5N1 to people around the globe appears to only be moderately higher than before the US cattle outbreak, but that even a slightly elevated risk is enough to raise concerns.
The most likely [outcome] is that it will die off, rather than posing a significant change and enough changes to actually spread in other countries, Munir Iqbal, head of the avian influenza and Newcastle Disease group at the Pirbright Institute, told Euronews Health.
But in places where H5N1 is already present, the virus is unseen, and therefore everything [should be] treated like something infectious.
Some countries are taking their own steps to prepare for H5N1, regardless of whether the US dairy cattle strain poses the ultimate threat in Europe.
Finland, for example, is offering vaccines to 10,000 workers who are at high risk of coming into contact with bird flu, and is also monitoring fur farms for potential cases throughout the summer.
Meanwhile, German and Italian researchers have tested samples from cattle and goats in areas where the virus has circulated among birds in recent years, and found no evidence that they were infected.
Kuiken said several other European countries, including the Netherlands, Spain, Norway, Sweden, France, and Belgium, will soon launch their own studies.
When you all of a sudden realise that a species that you haven't been paying much attention to could have been infected, you want to look retrospectively to see whether it occurred, Kuiken said.
Looking into the future, many labs are now taking into account that they can't rule out the possibility that such unusual epidemiological events also will happen in Europe.
The European Commission is also stockpiling 665,000 doses of pre-pandemic vaccines, which help protect against flu strains with pandemic potential, and could buy another 40 million doses if needed.
The international vaccine consortium Coalition for Epidemic Preparedness Innovations (CEPI) is convening an expert group to support global access to H5N1 vaccines, if the situation escalates.
But for now, in Europe, surveillance of H5N1 is key, Dr Ruth Harvey, deputy director of the Worldwide Influenza Centre at the Francis Crick Institute, told Euronews Health.
We can do the risk assessments, and then we can react accordingly, Harvey said.
The US outbreak is not the only one on experts radars.
Cases of avian flu caused by different strains have been reported in India, China, Australia, and Mexico, where an infected person had no known exposure to animals and eventually died from their illness.
Russell said that beyond the dairy cattle crisis, all countries should be tracing animal pathogens for potential spillover into humans and setting up reporting infrastructure to share this information quickly with the international community.
There is an opportunity in this particular situation for there to be a call to arms for extra vigilance against these viruses globally, Russell said.
