Category: Flu Virus

In a recent scientific report published in the European Food Safety Authority (EFSA) journal, a large team of researchers from the EFSA and European Centre for Disease Prevention and Control (ECDC) discussed the intrinsic and extrinsic drivers for a potential pandemic due to evolved avian influenza viruses, and risk mitigation measures that are part of the One Health approach.

Report: Drivers for a pandemic due to avian influenza and options for One Health mitigation measures. Image Credit:Pordee_Aomboon/ Shutterstock

Wild bird populations in the European Economic Area (EEA) and the European Union (EU) are known to have a high prevalence of avian influenza viruses that cause significant disease and mortality. Outbreaks have also been reported from fur animal farms, where the avian influenza viruses are thought to have been transmitted from birds to mammals. These infections among fur animals are believed to be due to transmission of the virus from birds to various mammalian species and possibly also because of transmission between mammalian species.

Although cases of transmission of these viruses from birds to humans have not been widely reported, the evolution of avian influenza viruses and the dispersal of the virus through migratory wild birds could result in the selection of viruses that can infect humans.

Given that humans do not yet have robust immune defenses against avian influenza viruses, the emergence of a virus capable of infecting and rapidly spreading among humans poses the risk of a potential pandemic. Examining the intrinsic and extrinsic drivers that can facilitate the evolution of avian influenza viruses to infect humans and to develop effective mitigation measures is imperative.

Factors such as susceptibility of the host and viral characteristics, known as intrinsic drivers, and extrinsic drivers, such as environmental factors, human activities, and climate, can facilitate the emergence of avian influenza viruses that carry mutations that allow them to infect mammals.

Viral characteristics such as the reassortment propensity can drive the avian influenza virus to adapt to mammalian hosts. The hemagglutinin 5 neuraminidase 1 (H5N1) or avian influenza A virus, which contains the 2.3.4.4b clade that is currently circulating, has displayed evolutionary changes that could allow it to infect mammals and reassort. Furthermore, the global prevalence of the H5N1 virus in birds, including heterogenous poultry livestock, could result in the accumulation of various mutations that enable the virus to infect mammals, especially humans.

Reassortment can also lead to rapid genetic shifts that allow the virus to infect and replicate in humans and transmit among human populations. Coinfection of mammals with seasonal influenza and avian influenza virus could also increase the probability of reassortment events.

Furthermore, fur animals such as foxes and minks are highly susceptible to influenza viruses, and the exposure of these mammals to highly pathogenic strains of the avian influenza virus through contaminated feed could drive the virus's adaptation to mammals. Outdoor production farms and those with proximity to areas rich in water birds provide more opportunities for the virus to be introduced into farms. Peri-urban and synanthropic wild animals could also facilitate the spread of the virus from wild birds to humans and animals.

Habitat destruction, extreme climatic events, and weather conditions can also impact the demography and ecology of these wild bird populations, acting as extrinsic drivers of the evolution of the avian influenza virus.

Risk mitigation measures included in the One Health approach suggested surveillance among target animal and human populations along with the generation and sharing of genomic data. Target animals included wild and captive birds, poultry, susceptible domestic mammals such as fur animals, cats, pigs, and peri-domestic and peri-urban mammals.

The measures also comprised development and access to sustainable, rapid diagnostic methods using genomic data to screen for avian influenza virus in relevant populations. An additional critical area for risk mitigation was occupational safety in areas where humans interact closely with target animals. Furthermore, reassortment risk can be reduced by vaccinating individuals with a higher probability of occupational exposure to avian influenza against the seasonal influenza virus.

The scientific report also discussed other areas, such as improving the veterinary infrastructure, biosecurity, communicating the risk to various audiences, and vaccinating animals, which could help mitigate the risk of the avian influenza virus adapting to humans and animals.

In summary, this report by the EFSA provided a detailed discussion of various intrinsic and extrinsic drivers, such as viral characteristics, factors that increase the susceptibility of animals, and environmental factors that could accelerate the adaptation of avian influenza viruses to mammalian hosts. The scientists also expanded on various mitigation measures, at individual and community levels, that could be followed to reduce the risk of adaptation and transmission of the avian influenza virus among animal and human populations.

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Avian flu's leap to humans: Understanding risks and prevention strategies - News-Medical.Net

The HPAI A(H5N1) virus, otherwise known as avian influenza or the bird flu, was recently detected in a dairy farmer in Texas. Its the first report of bird flu in the US since April 2022. The CDC released a statement on the status of the virus in the country and issued recommendations on how to avoid it.

The CDC issued a statement discussing avian influenza and is currently working with the USDA, FDA, and state departments to monitor the virus within the US. The overall risks of the virus growing into a larger public health issue, however, remains low, according to the CDC.1

Avian influenza is often detected in wild birds and poultry farms across the US | image credit: Dewald / stock.adobe.com

READ MORE: Are We Close to a Universal Flu Vaccine?

For just the second time, someone in the US has contracted avian influenza. It is highly pathogenic, yet no severe illness or death has occurred in the US due to the virus, with only 900 cases detected worldwide.1

The CDC has informed the public on where bird flu originates, the symptoms to look out for, and recommendations on how to treat and, most importantly, avoid the avian bird flu.

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Bird Flu Virus Detected in US for First Time in 2 Years - Drug Topics

In a study published today in the prestigious journal Nature, Siddharth Balachandran, PhD, and researchers have shown that a newly developed compound was able to block necroptosis, a type of cell death that leads to lung inflammation and damage following infection with the influenza virus.

PHILADELPHIA (April 10, 2024) In a study published today in the prestigious journal Nature, researchers from Fox Chase Cancer Center have shown that a newly developed compound was able to block necroptosis, a type of cell death that leads to lung inflammation and damage following infection with the influenza virus. Click HERE for study.

Necroptosis is triggered by the activation of the receptor interacting protein kinase 3 (RIPK3) pathway. This type of cell death produces strong immune responses by rupturing dead cells and releasing their contents throughout the body. When controlled, this form of cell death is effective at ridding the body of a virus. However, if unchecked, necroptosis can cause severe inflammation and lung damage and can even lead to death.

We have now shown the possibility that RIPK3 can be inhibited, which is significant because it is central to programmed necrotic death in human tissues. Any disease involving chronic inflammation and necrotic death, such as colitis, lung fibrosis, liver disease, or psoriasis, could potentially benefit from blockade of this pathway, said Siddharth Balachandran, PhD, lead author on the study and a Professor in the Cancer Signaling and Microenvironment Research Program at Fox Chase.

We found that by blocking necroptosis, you dont get this form of explosive death and its resultant inflammation, added Balachandran, who is also one of the Basic Science Co-Leaders of the Center for Immunology at Fox Chase.

He and his colleagues used mice infected with the flu virus to show that a newly developed RIPK3 inhibitor called UH15-38 selectively blocked necroptosis and dampened inflammation even when administered later in the course of an infection, a milestone in viral infection research.

The new study comes on the heels of previous research in 2020 identifying a fundamental mechanism that detects the presence of the flu virus and rapidly destroys infected cells. In this research, Balachandran and colleagues identified a protein called ZBP1, which they later learned detects Z-RNA, a new form of RNA that is produced by the flu virus.

When ZBP1 senses Z-RNA, it interprets this as a sign that the cell is infected and pushes an auto-destruct button that not only kills the infected cell but also alerts the immune system to the presence of the virus, said Balachandran.

This mechanism could have implications for a variety of fields, including immunotherapy in the treatment of cancer, which is currently ineffective for 70% to 80% of patients. In these cases, the immune system does not recognize the cancer as foreign.

Indeed, Balachandrans work grows out of a long history of basic research at Fox Chase that can have unexpected applications in many areas of medicine. In 2022, he published another study in Nature that showed that a drug candidate may help reinitiate immune responses by mimicking influenza virus infections in patients whose cancer is unresponsive to immunotherapy.

As a result of that study, Fox Chase is currently conducting a phase 1 clinical trial in which a compound known as CBL0137 is used alongside immunotherapy drugs in melanoma patients to reactivate an immune response in tumors and rekindle immunotherapy effectiveness.

Its really important to study the bodys immune responses to pathogens so that we know how the immune system responds normally to what its meant to respond to. The majority of current cancer therapeutics have come from people studying normal cells and normal biology, and not the cancer cell itself, Balachandran said.

The immediate translational potential of this work is important. Without our prior research in the general areas of viral infections, we would not have discovered that viruses activate necroptosis and we therefore wouldnt have been able to identify a compound that mimics virus infections and triggers on-demand necroptosis in tumors, said Balachandran. Basic research is fundamental to new drug discovery.

Additionally, he noted the growing need for basic research in the area of viral infections. In the wake of the COVID-19 pandemic, it is more important than ever to search for solutions that focus on the bodys response to viruses rather than only working to develop new vaccines.

The next pandemic could very well be from a new strain of the influenza virus, and there are no effective vaccines or therapeutics for influenza yet because targeting the virus is difficult, said Balachandran.

Thats the reason I think we need a therapy that targets the bodys response to the virus. This way youre blocking a host pathology, so you dont have to worry about resistance. Thats one of the major advantages of this study and why understanding how these biological processes work in normal settings is key to finding new anti-inflammatory and anticancer therapies.

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Fox Chase Cancer Center Study Demonstrates Promise of New Therapy for Lung Injury From Severe Flu Infection - Fox Chase Cancer Center

Bird flu expert Suresh Kuchipudi on the pathogenesis of H5N1 and threats it poses

Photo: iStock

H5N1, or bird flu, has been perceived as a potential public health threat for at least 20 years now, since the virus infected some 18 people in China. Much recently, in 2022, the United States recorded its first human infection of avian influenza. Then, this April, a man in the US state of Texas contracted the disease from cows, creating an alarm in the global health community.

Although the virus mainly spreads among birds, its pan-zootic profile is not unknown. But with every transmission to humans from a mammalian species, it becomes certain that H5N1 is growing more adaptive and the possibility of a human-to-human transmission becomes stronger, according to experts.

There have also been speculation that bird flu can snowball into a pandemic. Its high virulence and fatality rate were highlighted in a news story published in the Daily Maildays after the Texas case.The story quoted Suresh Kuchipudi, a bird flu scientist in Pittsburgh, as saying: Now, we are getting dangerously close to this virus potentially causing a pandemic. He higlighted that the world needs to be prepared for such a global health challenge.

Down To Earth spoke to Kudhipudi to understand the tendencies of the virus and the threats that it poses.

Himanshu Nitnaware: H5N1 has started assuming a deadly hue, particularly after we have just emerged from a global pandemic. Will you elaborate on this bird flu virus?

Suresh Kuchipudi: Bird flu viruses belonging to the H5N1 strain have been present for a long time. The original H5N1 virus was first identified in 1996 in a goose in China. These viruses later spread globally and underwent significant genetic changes and generated multiple subtypes.

The current bird flu virus subtype is known as H5N1 virus clade 2.3.4.4b, which initially emerged in Europe in the late 2020 and spread to many countries, causing significant outbreaks across multiple continents. Mass mortality events involving 2.3.4.4b clade viruses have been observed in several avian and mammalian species, including minks and sea mammals. The more recent development in this virus journey is the infection of cattle in the United States and a confirmed cow-to-human infection.

HN: It is not that a new virus has been circulating. Why should we be worried about it now?

SK: The current subtype of the bird flu virus has shown an alarming ability to infect a wider array of wild birds and mammals. As it circulates among multiple hosts, there is a higher likelihood of genetic mutations, increasing the risk of viral evolution and potential adaptation to mammals.

HN: Since 2022, we have witnessed a few human infections. But is the number that high to be worried about? Or, in the evolutionary cycle of a virus, this breach is already worrying?

SK: Human infections with H5N1 viruses have been documented over time, so the recent case of a Texas man infected with H5N1 isnt entirely novel. However, whats concerning is the unprecedented transmission among cattle before infecting a human. This situation presents multiple opportunities for the virus to infect diverse mammalian hosts, heightening the likelihood of adaptation.

HN: Bird flu is already on the scale of a pandemic. Do you see a particularly increasing infection and circulation of bird flu viruses in recent times? Does this imply that the next pandemic to hit humans will be from this source?

SK: The global distribution of H5N1 viruses primarily affects poultry, making them panzootic among birds. However, the concern arises from their potential to transition into a human virus, potentially triggering a human pandemic.

HN: If it causes the next pandemic, will it be a severe one, comparable to the COVID-19 one?

SK: While we cannot accurately predict the severity of the virus after gaining human-to-human transmission capability, its prudent to assume, for preparedness in a global health emergency, that its likely to cause more severe disease in humans than COVID-19, based on current information.

HN: The virus cannot survive on a dead body, it requires the host to be alive for its existence. If it does become deadly, how can infection-spread behaviour be known?

SK: SARS-CoV-2, the cause of the COVID-19 pandemic, primarily spread among humans globally. The potential occurrence of a H5N1 bird flu pandemic could introduce complexity in virus circulation involving both humans and other animal hosts. This scenario could pose significant challenges for mitigation and control efforts.

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'Wise to assume bird flu pandemic will cause more severe disease in humans than COVID-19' - Down To Earth Magazine

The U.S. Centers for Disease Control on Friday issued a health alert for bird flu after a Texas dairy cow worker tested positive for the virus earlier this week.

The workers infection marked the second recorded case among humans of avian influenza, or A(H5N1), in the U.S., according to experts, and comes amid a spike in recorded cases in dairy cattle and chickens.

Days after the largest U.S. producer of fresh eggs paused production and slaughtered nearly 2 million birds after detecting the virus in its flock, experts from Texass top public health agency and the University of Texass Health Science Center spoke with the Landing about the state of the outbreak (spoiler: no cause for alarm just yet, Houston).

Check out their responses to Houstons most urgent bird flu questions:

H5N1, The current strain of avian influenza spreading among dairy cattle and poultry, is a common virus that spreads easily among other non-human animals.

H5N1 has actually been detected in all kinds of random animals, said Dr. Michael Chang, an infectious disease specialist at the UT Health Science Center in Houston. A lot of migratory birds like ducks and geese carry it and dont get as sick. But when a chicken gets it, it gets really sick.

The only two recorded human cases of H5N1 in the U.S. were detected among dairy and poultry workers in close contact with infected animals. The average Houstonian probably does not have to worry about catching bird flu, Texas Department of State Health Services spokesperson Chris Van Deusen explained.

For the rest of us, the probability of transmission is very low, Van Deusen said. His advice? Avoid dead birds, especially ducks or geese, or other migratory birds.

Luckily, theres no mutation that seems to make [H5N1] more transmissible amongst humans, Chang echoed.

In both the samples that have come from cows and from the human cases, there has not been an adaptation or a mutation in the virus that would lead it to be more likely to spread among people, he explained. So during this outbreak specifically, it doesnt appear that theres a big risk for rapid human transmission.

Technically, yes. But your chances are extremely low, especially if you dont like runny yolks.

The response to avian flu in general and the food chain of production, like infrastructure for chickens, is really rapid. So theres a low probability that a chicken contaminated with the virus will get into the food supply chain, Chang said.

Milk from dairy cows is still safe to drink, too. The milk we have in the U.S. that you can buy in a store is all pasteurized and pasteurization will kill the flu virus, Chang said.

Texas DSHS said in an April 1 release that patients presenting with eye redness, fever, cough, sore throat, or other symptoms associated with the typical flu after a confirmed close contact with a potentially infected animal should be screened for the virus.

The symptoms in people are not always consistent, Chang warned. So we dont always know.

Recorded cases of bird flu in dairy cattle and chickens have spiked across the U.S. in recent weeks. One of the two human bird flu cases was detected in Texas.

The largest fresh egg producer in the U.S. paused production at one of its Texas facilities and slaughtered nearly 2 million chickens after detecting the virus in the flock.

Infectious disease experts say the virus is not showing signs of mutations that would lead to rapid spread from animals to humans, or from one human to another. But theyre still keeping a close eye on the outbreak among livestock.

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A human bird flu case was detected in Texas. Here's what to know. - The Houston Landing

Agriculture officials have detected avian influenza in dairy herds across the country.

The U.S. Department of Agriculture first confirmed avian flu in dairy herds in Kansas and Texas late last month. Since then, cases in Michigan, Ohio, Idaho and New Mexico have also been confirmed.

No cases have been detected in dairy cows or humans in Wisconsin, but state leaders are urging dairy farmers to take extra precautions against the spread of avian flu.

To learn more about how the virus could impact Wisconsins dairy industry, Lake Effect spoke with Dr. Keith Poulsen, a veterinarian and director of theWisconsin Veterinary Diagnostic Laboratory.

This interview has been edited and condensed for length and clarity.

What do we know about this current strain of avian flu?

Poulsen explains that Wisconsin has been dealing with this particular strain of highly pathogenic avian influenza since 2022. In this case, migratory birds are spreading HPAI mostly to dairy cows in their second lactation cycle. He says theres three important points to know right now:

One, pasteurized dairy products are safe, and so is meat if cooked properly," Poulsen says. Two, these cows are not dying. Its very different than what we've seen in our poultry flocks where we've seen high mortality. Number three, is that we don't really consider this an extremely high threat to public health at this time.

How is the virus spreading to dairy cows?

Poulsen says animal health officials first thought that the virus was primarily spreading from migratory birds to cows and not going beyond that. But after further research, he says officials have noticed a spread of the virus among dairy herds moving from Texas into other states like Ohio, Michigan and Idaho.

Now, what exactly is causing cow-to-cow transmission? That's a kind of up for debate, Poulsen explains. At this point, I don't think we have enough information.

He says that the virus affecting dairy cows is acting more like a low-path strain of influenza. Whereas, when poultry flocks are affected by a high-path strain, theyre humanely euthanized.

We're not seeing that mortality [in dairy cows], so it's kind of a misnomer, Poulsen says. We're working on that messaging of this really isn't high-path influenza in cows, because the cows are not dying. It's more of the same strain [affecting poultry flocks], but it's causing low pathogenicity or much less severe clinical signs in our dairy cows of a very particular part of their lactation and theyre older [too]. Which is a novel way of seeing clinical disease due to influenza in cows.

Should the spread of avian flu be of concern to Wisconsin dairy farmers right now?

Poulsen emphasizes that pasteurized dairy products are still safe to be consumed, and is deemed safe by the Food and Drug Administration and the U.S. Department of Agriculture.

However, a main concern that farmers are facing right now is the risk of bringing back avian influenza into their dairy herds.

It is very, very common in the northern and the Midwestern states to actually send their calves to Kansas and Texas in warmer climates [during winter months]," Poulsen explains. Because it's much more efficient, it's more cost effective, and the health of their calves are better, and then they come back when they're springing heifers. That's the most common way that we see cows coming back into the state of Wisconsin. And of those animals, that's where I think a lot of our dairy producers are concerned about Well, am I bringing influenza back into my herds?

Poulsen says agriculture officials and animal health leaders across the state are urging Wisconsin dairy producers to take extra precautions against the spread of the virus by following biosecurity guidelines. That includes possible diagnostic testing and closely monitoring animals, with the guidance of USDA officials, once they are transported back to the farm.

The strain that we're seeing circulating in cattle right now, we don't have any cases in Wisconsin, Poulsen says. All the cases that we've seen in Ohio, Michigan, and Idaho, have been from transporting lactating cows into dairy herds, which is really not as common as what we see in Wisconsin transporting pregnant animals. So we're really hoping that our risks there are much lower.

How much of a risk does the virus pose to humans?

Last week, Texas health officials reported that a person in direct contact with infected dairy cows tested positive for the virus. The Texas agency stated that the patient experienced conjunctivitis, similar to pink eye, as their only symptom and is being treated with the antiviral drug oseltamivir.

Its the second confirmed human case of H5N1 flu in the U.S. and the first linked to exposure to cattle, according to the CDC.

Poulsen says the CDC, USDA and FDA continue to deem thehealth risk to humans as low.

What we can do on [dairy] farms is make sure we have personal protective equipment available [such as] safety glasses with shields, or just having the face shield in front, wearing gloves and dedicated clothing," he says.

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Wisconsin veterinarian gives insight to the bird flu virus making dairy cows sick in other states - WUWM

Jackson talked about the virus during a Friday morning internet briefing that UVA Health held for news media.

Officially known as avian influenza A (H5N1), the virus is spread through bird saliva, mucous and feces.The virus can spread to domestic birds and other animals.Human infections can happen when enough virus gets into a persons eyes, nose or mouth, or is inhaled, but and this is the key it is extremely rare for it to be transmitted from one person to another.

The Texas mans case is the second reported case in the U.S. of humans catching the current strain of avian flu. The other case occurred in Colorado in 2022 and involved a chicken farmer culling birds infected with the virus.

There have been more cases around the world, but only in small numbers, according to CDC figures. In February, four people in Cambodia were reported to have avian flu, including three children. One died.

All patients reportedly had a history of recent exposure to sick or dead poultry prior to their illness, the CDC stated. Currently, there is no indication of person-to-person spread associated with these four cases of H5N1 virus infection in Cambodia, and they are not thought to pose a threat to the health of the U.S. public.

Jackson, the Texas health department and the CDC all agree that for most people, the virus poses little danger. Pasteurization of milk, and dairy farmers destroying any milk taken from ill animals, should limit that possible transmission route.

Poultry farms often destroy flocks of chickens that have been exposed to avian flu as a means of stopping the virus spread and protecting customers.

Still, state and federal health officials and infectious disease physicians are keeping tabs on the virus out of caution.

Humans are always at risk for new infections, in part because we live in close proximity to animals. Plus, the human population is increasing and we travel much more efficiently, so its quite easy for a new infection one place in the world get to other places in the world, Jackson said.

Aviral spread from animals to humans is essentially how every pandemic in history has occurred. In fact, we likely saw that with COVID-19 just recently, he said. That being said, the simple fact that one individual human was infected with this virus doesnt mean that its well-adapted to spread from human to human and cause a big problem right now.

As long as were doing what we can to monitor the situation and to make appropriate preparations, I dont think theres any reason for people who are otherwise at normal risk to be particularly alarmed about this, he said.

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A Bird Flu Over Texas: No Need To Fear Here - UVA Today

Animal health officials in Vietnam and with the United Nations Food and Agriculture Organization (FAO) today urged countries to be on alert for a new highly pathogenic avian influenza (HPAI) H5N1 reassortant virus in chickens and mescovy ducks, which was found during active surveillance.

In a statement, the FAO said the virus is a reassortant between the older H5N1 clade (2.3.2.1c) that is still circulating in parts of Asia and a newer H5N1 clade (2.3.4.4b) that began circulating globally in 2021.

The reassortant virus contains surface proteins of the older clade virus and internal genes from the more recent virus clade. The reassortant has been circulating across the Greater Mekong subregion, causing infections in birds and people since the middle of 2022.

The FAO said the virus has been linked to human infections, though it didn't specify which ones.

It said the reassortant virus poses a significant threat to animal and human health, given the impact of HPAI outbreaks in the region. "Further, this reassortment event indicates not only the adaptive capacity of the virus but also the ever-present risk of the emergence of new, potentially more virulent strains," the FAO said.

This reassortment event indicates not only the adaptive capacity of the virus but also the ever-present risk of the emergence of new, potentially more virulent strains.

Surveillance in Vietnam shows that the older clade is mainly circulating in the southern part of the country and the newer clade is circulating throughout the country. The reassortant turned up in a small number of samples from poultry markets in Vietnam's southern provinces in 2023, but scientists did not detectthe worrisome PB2-E627K substitution, which is known to play a role in mammalian adaptation.

The report didn't clarify which recent human cases involved the reassortant. It said that, since December 2023, five human H5N1 cases were reported in Cambodia, of which the first four involved the older virus clade which has detected in Cambodian poultry since 2014.

Of the five cases, most were serious and one was fatal. Patients had a history of contact with poultry.

A notification 3 days ago from the World Health Organization (WHO) on Vietnam's latest case, which involved a 21-year-old man who died from his infection, did not have any details about which H5N1 clade.

The FAO said the overall public health risk from H5N1 hasn't changed and the virus isn't likely to trigger sustained human-to-human infections.

Officials from Vietnam's health department and the FAO urged farmers, poultry traders, and veterinarians to strengthen their biosecurity measures and recommended that the public take food safety steps, such as frequent hand washing after during food preparation and when handling animals.

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Officials warn of H5N1 avian flu reassortant circulating in parts of Asia - University of Minnesota Twin Cities

The United States Centers for Disease Control and Prevention (CDC) has issued a health alert after the first case of H5N1 avian influenza, or bird flu, seemingly spread from a cow to a human.

A farm worker in Texas contracted the virus amid an outbreak in dairy cattle. This is the second human case in the US; a poultry worker tested positive in Colorado in 2022.

The virus strain identified in the Texan farm worker is not readily transmissible between humans and therefore not a pandemic threat. But its a significant development nonetheless.

There are two types of avian influenza: highly pathogenic or low pathogenic, based on the level of disease the strain causes in birds. H5N1 is a highly pathogenic avian influenza.

H5N1 first emerged in 1997 in Hong Kong and then China in 2003, spreading through wild bird migration and poultry trading. It has caused periodic epidemics in poultry farms, with occasional human cases.

Influenza A viruses such as H5N1 are further divided into variants, called clades. The unique variant causing the current epidemic is H5N1 clade 2.3.4.4b, which emerged in late 2020 and is now widespread globally, especially in the Americas.

In the past, outbreaks could be controlled by culling of infected birds, and H5N1 would die down for a while. But this has become increasingly difficult due to escalating outbreaks since 2021.

Read more: When should we worry about bird flu making us sick? When we see human-to-human transmission and there's no evidence of that yet

Waterfowl (ducks, swans and geese) are the main global spreaders of avian flu, as they migrate across the world via specific routes that bypass Australia. The main hub for waterfowl to migrate around the world is Quinghai lake in China.

But theres been an increasing number of infected non-waterfowl birds, such as true thrushes and raptors, which use different flyways. Worryingly, the infection has spread to Antarctica too, which means Australia is now at risk from different bird species which fly here.

H5N1 has escalated in an unprecedented fashion since 2021, and an increasing number of mammals including sea lions, goats, red foxes, coyotes, even domestic dogs and cats have become infected around the world.

Wild animals like red foxes which live in peri-urban areas are a possible new route of spread to farms, domestic pets and humans.

Dairy cows and goats have now become infected with H5N1 in at least 17 farms across seven US states.

Globally, there have been 14 cases of H5N1 clade 2.3.4.4b virus in humans, and 889 H5N1 human cases overall since 2003.

Previous human cases have presented with a severe respiratory illness, but H5N1 2.3.4.4b is causing illness affecting other organs too, like the brain, eyes and liver.

For example, more recent cases have developed neurological complications including seizures, organ failure and stroke. Its been estimated that around half of people infected with H5N1 will die.

The case in the Texan farm worker appears to be mild. This person presented with conjunctivitis, which is unusual.

Contact with sick poultry is a key risk factor for human infection. Likewise, the farm worker in Texas was likely in close contact with the infected cattle.

The CDC advises pasteurised milk and well cooked eggs are safe. However, handling of infected meat or eggs in the process of cooking, or drinking unpasteurised milk, may pose a risk.

Although theres no H5N1 in Australian poultry or cattle, hygienic food practices are always a good idea, as raw milk or poorly cooked meat, eggs or poultry can be contaminated with microbes such as salmonella and E Coli.

Scientists have feared avian influenza may cause a pandemic since about 2005. Avian flu viruses dont easily spread in humans. But if an avian virus mutates to spread in humans, it can cause a pandemic.

One concern is if birds were to infect an animal like a pig, this acts as a genetic mixing vessel. In areas where humans and livestock exist in close proximity, for example farms, markets or even in homes with backyard poultry, the probability of bird and human flu strains mixing and mutating to cause a new pandemic strain is higher.

The cows infected in Texas were tested because farmers noticed they were producing less milk. If beef cattle are similarly affected, it may not be as easily identified, and the economic loss to farmers may be a disincentive to test or report infections.

For now there is no spread of H5N1 between humans, so theres no immediate risk of a pandemic.

However, we now have unprecedented and persistent infection with H5N1 clade 2.3.4.4b in farms, wild animals and a wider range of wild birds than ever before, creating more chances for H5N1 to mutate and cause a pandemic.

Unlike the previous epidemiology of avian flu, where hot spots were in Asia, the new hot spots (and likely sites of emergence of a pandemic) are in the Americas, Europe or in Africa.

Pandemics grow exponentially, so early warnings for animal and human outbreaks are crucial. We can monitor infections using surveillance tools such as our EPIWATCH platform.

The earlier epidemics can be detected, the better the chance of stamping them out and rapidly developing vaccines.

Although there is a vaccine for birds, it has been largely avoided until recently because its only partially effective and can mask outbreaks. But its no longer feasible to control an outbreak by culling infected birds, so some countries like France began vaccinating poultry in 2023.

Read more: Migrating birds could bring lethal avian flu to Australia's vulnerable birds

For humans, seasonal flu vaccines may provide a small amount of cross-protection, but for the best protection, vaccines need to be matched exactly to the pandemic strain, and this takes time. The 2009 flu pandemic started in May in Australia, but the vaccines were available in September, after the pandemic peak.

To reduce the risk of a pandemic, we must identify how H5N1 is spreading to so many mammalian species, what new wild bird pathways pose a risk, and monitor for early signs of outbreaks and illness in animals, birds and humans. Economic compensation for farmers is also crucial to ensure we detect all outbreaks and avoid compromising the food supply.

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A person in Texas caught bird flu after mixing with dairy cattle. Should we be worried? - The Conversation

Were just a couple of weeks away from May, which marks the official start of the influenza season in Australia. So what can we expect from the upcoming flu season and when is the best time to get your annual flu vaccine?

Learn more about flu vaccination, virus variants and current influenza surveillance from Virologist and Director of the World Health Organization Collaborating Centre for Reference and Research on Influenza, Professor Kanta Subbarao.

Show notes:

Learn more about Influenza vaccination and the National Immunisation Program via the Australian Government Department of Health and Aged Care website.

Interested in the work of the WHO Collaborating Centre for Reference and Research on Influenza at the Doherty Institute? Visit the Centre website.

Check out our episode on avian influenza: Avian influenza (H5N1): why are experts concerned about the virus reaching Antarctica?

Find out about recent announcement of funding from the Novo Nordisk Foundation to develop a novel antiviral drug to counter influenza.

Get in touch

Have a question or topic you'd like us to explore in a future episode? Contact us via email doherty-media@unimelb.edu.au

Excerpt from:

Here's what you need to know about flu season 2024 - The Peter Doherty Institute for Infection and Immunity