Virus World

Avian influenza (serotype H5N1) is a highly pathogenic virus that emerged in domestic waterfowl in 1996. Over the past decade, zoonotic transmission to mammals, including humans, has been reported. Although human to human transmission is rare, infection has been fatal in nearly half of patients who have contracted the virus in past outbreaks. The increasing presence of the virus in domesticated animals raises substantial concerns that viral adaptation to immunologically naive humans may result in the next flu pandemic. Wastewater-based epidemiology (WBE) to track viruses was historically used to track polio and has recently been implemented for SARS-CoV2 monitoring during the COVID-19 pandemic.

Here, using an agnostic, hybrid-capture sequencing approach, we report the detection of H5N1 in wastewater in nine Texas cities, with a total catchment area population in the millions, over a two-month period from March 4th to April 25th, 2024. Sequencing reads uniquely aligning to H5N1 covered all eight genome segments, with best alignments to clade 2.3.4.4b. Notably, 19 of 23 monitored sites had at least one detection event, and the H5N1 serotype became dominant over seasonal influenza over time. A variant analysis suggests avian or bovine origin but other potential sources, especially humans, could not be excluded. We report the value of wastewater sequencing to track avian influenza.

Preprint in medRxiv ( May 10, 2024):

https://www.medrxiv.org/content/10.1101/2024.05.10.24307179v1.full.pdf 

The U.S. must act decisively, acknowledging the potential gravity of H5N1 mammalian transmission. Humans have no natural immunity to the bird flu virus. 

The recent detection of H5N1 bird flu in U.S. cattle, coupled with reports of a dairy worker contracting the virus, demands a departure from the usual reassurances offered by federal health officials. While they emphasize there’s no cause for alarm and assert diligent monitoring, it’s imperative we break from this familiar script. H5N1, a strain of the flu virus known to infect bird species globally and several mammalian species in the U.S. since 2022, has now appeared to have breached a new barrier of inter-mammalian transmission, as exemplified by the expanding outbreak in dairy cows in several jurisdictions linked to an initial outbreak in Texas. Over time, continued transmission among cattle is likely to yield mutations that will further increase the efficiency of mammal-to-mammal transmission. As the Centers for Disease Control continues to investigate, this evolutionary leap, if confirmed, underscores the adaptability of the H5N1 virus and raises concerns about the next step required for a pandemic: its potential to further evolve for efficient human transmission. Because humans have no natural immunity to H5N1, the virus can be particularly lethal to them. Despite assertions of an overall low risk of H5N1 infection to the general population, the reality is that the understanding of this risk is limited, and it’s evolving alongside the virus. The situation could change very quickly, so it is important to be prepared.

Comparisons to seasonal flu management underestimate the unique challenges posed by H5N1. Unlike its seasonal counterparts, vaccines produced and stockpiled to tackle bird flu were not designed to match this particular strain and are available in such limited quantities that they could not make a dent in averting or mitigating a pandemic, even if deployed in the early stages to dairy workers. The FDA-approved H5N1 vaccines — licensed in 2013, 2017, and 2020 — do not elicit a protective immune response after just one dose. Even after two doses, it is unknown whether the elicited immune response is sufficient to protect against infection or severe disease, as these vaccines were licensed based on their ability to generate an immune response thought to be helpful in preventing the flu. Early studies done by mRNA vaccine companies on seasonal flu are promising, which could be good news here since mRNA vaccines can be made more quickly than vaccines using eggs or cells. Congressional funding is needed to catalyze rapid vaccine development and production. While FDA-approved antiviral drugs like Tamiflu and Xofluza could be an important line of defense against H5N1, logistical barriers impede their timely administration, as they work best when given as early as possible within 48 hours of the onset of symptoms. Most Americans would find it challenging to get a prescription filled for these medicines within the optimal time frame. Streamlining access to stockpiled antiviral drugs through improved test-to-treat measures like behind-the-counter distribution or dedicated telemedicine consultations could vastly improve their effectiveness as a frontline defense. Making plans to do that need to start now.

For vulnerable people — older adults and anyone who is immunocompromised — clinicians have become accustomed to relying on monoclonal antibodies. Sadly, their performance for flu has been disappointing in many clinical trials and can’t be counted on. The need for robust diagnostic capabilities cannot be overstated. H5N1 will not be detected by the typical rapid flu antigen tests that are administered in emergency rooms and many doctors’ offices. New tests will have to be made from scratch. The dismantling of diagnostic infrastructure post-Covid-19 and supply chain disruptions, however, pose significant challenges to the availability of such tests. Rapid investment in diagnostic testing, coupled with efforts to secure essential materials, is imperative to ensure timely detection and antiviral treatment. President Biden’s emphasis on infrastructure presents a unique opportunity to fortify America’s defenses against infectious diseases. A national initiative to enhance indoor air quality in schools and communal spaces could mitigate transmission risks should this virus learn how to efficiently be transmitted between humans, and would pay dividends every respiratory virus season and for years to come. In the face of uncertainty, complacency is not an option. The U.S. must act decisively, acknowledging the potential gravity of the H5N1 situation while leveraging every available resource to safeguard public health. The stakes are too high to repeat past mistakes.

Luciana Borio is an infectious disease physician, a senior fellow for global health at the Council on Foreign Relations, a venture partner at ARCH Venture Partners, and former director for medical and biodefense preparedness policy at the National Security Council. Phil Krause is a virologist, infectious disease physician, and former deputy director of the Office of Vaccines Research and Review at the FDA. The authors have no links to any companies producing or evaluating any of the vaccines or therapies mentioned in this article, and declare no conflicts of interest.

Health Alert Network (HAN). Provided by the Centers for Disease Control and Prevention (CDC).

Summary

The Centers for Disease Control and Prevention (CDC) is issuing this Health Alert Network (HAN) Health Advisory to inform clinicians, state health departments, and the public of a recently confirmed human infection with highly pathogenic avian influenza (HPAI) A(H5N1) virus in the United States following exposure to presumably infected dairy cattle. The U.S. Department of Agriculture (USDA) recently reported detections of highly pathogenic avian influenza A(H5N1) virus in U.S. dairy cattle in multiple states. This Health Advisory also includes a summary of interim CDC recommendations for preventing, monitoring, and conducting public health investigations of potential human infections with HPAI A(H5N1) virus.

Background

A farm worker on a commercial dairy farm in Texas developed conjunctivitis on approximately March 27, 2024, and subsequently tested positive for HPAI A(H5N1) virus infection. HPAI A(H5N1) viruses have been reported in the area’s dairy cattle and wild birds. There have been no previous reports of the spread of HPAI viruses from cows to humans. The patient reported conjunctivitis with no other symptoms, was not hospitalized, and is recovering. The patient was recommended to isolate and received antiviral treatment with oseltamivir. Illness has not been identified in the patient’s household members, who received oseltamivir for post-exposure prophylaxis per CDC Recommendations for Influenza Antiviral Treatment and Chemoprophylaxis. No additional cases of human infection with HPAI A(H5N1) virus associated with the current infections in dairy cattle and birds in the United States, and no human-to-human transmission of HPAI A(H5N1) virus have been identified.

CDC has sequenced the influenza virus genome identified in a specimen collected from the patient and compared it with HPAI A(H5N1) sequences from cattle, wild birds, and poultry. While minor changes were identified in the virus sequence from the patient specimen compared to the viral sequences from cattle, both cattle and human sequences lack changes that would make them better adapted to infect mammals. In addition, there were no markers known to be associated with influenza antiviral drug resistance found in the virus sequences from the patient’s specimen, and the virus is closely related to two existing HPAI A(H5N1) candidate vaccine viruses that are already available to manufacturers, and which could be used to make vaccine if needed. This patient is the second person to test positive for HPAI A(H5N1) virus in the United States. The first case was reported in April 2022 in Colorado in a person who had contact with poultry that was presumed to be infected with HPAI A(H5N1) virus. Currently, HPAI A(H5N1) viruses are circulating among wild birds in the United States, with associated outbreaks among poultry and backyard flocks and sporadic infections in mammals....

In June 2023, a fatal disease outbreak in cats occurred in Poland. Most cases tested in Poland (29 of 47) were positive for highly pathogenic avian influenza (HPAI) A (H5N1) virus. Genetic analyses revealed clade 2.3.4.4b with point mutations indicative of initial mammalian hosts adaptations. Cat viral sequences were highly similar (n = 21), suggesting a potential common infection source. To investigate possible infection routes, our group tested food samples from affected households. HPAI H5N1 virus was detected in one poultry meat sample.

Highly pathogenic avian influenza virus (HPAIV) H5N1 was introduced in North America in late 2021 through trans-Atlantic pathways via migratory birds. These introductions have resulted in an unprecedented epizootic, a widespread disease event in animals, heavily affecting poultry, wild birds, and recently mammals. The North American incursions occurred during the largest epidemic season (2021–2022) in Europe where H5N1 may now be endemic (i.e., continuously present). The continuing outbreak includes expansion into Mexico, Central and South America beginning in late 2022. Here, we provide an overview of the Eurasian origin H5N1 introduction to the Americas, including a significant shift in virus dynamics and severe disease in wild birds.

Then, to investigate the global changes in confirmed detections in wild birds and poultry across time and geographic regions, we analyzed FAO's EMPRES-i + database. To examine the 2021 introduction and spread in North American wild birds and poultry, we collated publicly available data across USA and Canadian federal sources. Based on our assessment, the unique magnitude of the North American H5N1 spread indicates the need for effective decision framing to prioritize management needs and scientific inquiry, particularly for species at risk and interface areas for wildlife, poultry, and humans. We illustrate the rapidly occurring and likely increasing detrimental effects that this One Health issue has on wildlife, agriculture, and potentially human health, and we offer a reframing of HPAIV disease response towards a decision analytical context to guide scientific prioritization as a potentially valuable change in focus.

Published June 2023:

https://doi.org/10.1016/j.biocon.2023.110041 

Three California condors have died from avian flu in northern Arizona and authorities are trying to determine what killed five others in the flock, the National Park Service announced Friday.

A sick female condor suspected of having lead poisoning was found dead on March 20 and testing showed it had Highly Pathogenic Avian Influenza (HPAI), the park service said. Two other birds later found dead also tested positive, while test results aren't yet completed for five others, the park service said. The birds are part of a population that moves throughout northern Arizona and southern Utah, including Grand Canyon National Park, the park service said. The Peregrine Fund, which manages the Arizona-Utah flock, also captured five other birds that seemed ill and sent them to a wildlife rescue in Phoenix. One bird died and the other four have been quarantined, officials said. Exposure to the virus is expected to rise during the condors' northward spring migration. HPAI hasn't been detected in other populations in California or Mexico's Baja California, according to the park service. Avian flu occurs mainly in birds including domestic chickens, but it has been found in other animals, wild and domestic, in all U.S. states except Hawaii. Humans are considered to be at low risk from HPAI, although there have been reported infections. The

California condor is one of the world's largest birds with a wingspan of up to 10 feet (3 meters). The birds once patrolled the sky from Mexico to British Columbia. Condors can live for 60 years and fly vast distances, which is why their range can extend into several states. The population plummeted to the brink of extinction in the 1970s because of hunting, habitat destruction and lead poisoning from animals eating shot with lead bullets. In the 1980s, wildlife officials captured the last remaining 22 condors and took them to the San Diego and Los Angeles zoos to be protected and bred in captivity. The birds were then released into sanctuaries and national parks where they can be monitored. The birds have been protected as an endangered species by federal law since 1967 and by California state law since 1971. California condors have been making a comeback in the wild and now occupy parts of California's Central Coast, Arizona, Utah and Baja California, Mexico. The total wild population now numbers more than 300 birds.

Scientists identify three key changes needed to adapt the virus to mammals. The victims are varied, from thousands of sea lions off the coast of Peru to mink farmed for fur in Spain to grizzly bears in Montana and harbor seals in Maine. For months, the avian influenza virus that has been decimating birds across the world has also sickened and killed a menagerie of mammals, raising fears it might evolve to spread more efficiently between these animals, and ultimately between people. For that nightmare to unfold, however, the virus, a subtype known as H5N1, would have to undergo a major transformation, changing from a pathogen efficient at infecting cells in the guts of birds and spreading through feces-contaminated water into one adept at infecting human lung tissue and spreading through the air. So far, that has not happened. None of the few people who have caught the virus currently wiping out birds, called clade 2.3.4.4b, seems to have passed it on to other people. “This clade … is most of all and more than all previous clades an avian virus,” says virologist Martin Beer of the Friedrich Loeffler Institute. That is why it has spread so far and wide in birds, he says, and why it is so poor at infecting people. Beer and his colleagues in Berlin and Münster, Germany, have been using lung tissue taken from cancer patients undergoing surgeries, for instance, to see whether the virus can efficiently infect the human cells. So far, it cannot...

As the virus continues its spread to new species, the World Health Organization fears it is moving closer to people. The risk of bird flu jumping into humans is of “enormous concern,” the World Health Organization has warned as the virus continues its spread into new species. Since 2020, an outbreak of the H5N1 strain has killed tens of millions of birds worldwide, along with thousands of mammals, including sea lions, elephant seals and even one polar bear. More recently, the virus emerged in 16 herds of cattle in Texas – a development which has surprised experts, as it was previously believed the animals were not susceptible to infection, and raised concerns that H5N1 could eventually spill over into humans.

“This remains, I think, an enormous concern,” Dr Jeremy Farrar, the WHO’s chief scientist, told reporters on Thursday in Geneva. “When you come into the mammalian population, then you’re getting closer to humans … this virus is just looking for new, novel hosts.” He warned that, by circulating in new mammals, the virus improves its chances of further evolving and developing “the ability to infect humans and then critically the ability to go from human to human”. In the recent cattle outbreak in Texas, one person was diagnosed with bird flu following close contact with dairy cows presumed to have been infected.  Over the past 20 years, hundreds of others have caught the virus following exposure to an infected animal – yet there has been no evidence of human-to-human transmission in these cases. Yet the mortality rate for humans is “extraordinarily high,” Dr Farrar warned. From 2003 to 2024, 463 deaths and 889 cases were reported from 23 countries, according to the WHO – a case fatality rate of 52 per cent. The Texas infection is the second case of bird flu in the US and appears to have been the first infection of the H5N1 strain through contact with an infected mammal, said the WHO.

Dr Farrar said the ongoing bird flu outbreak had become “a global zoonotic animal pandemic” and called for increased monitoring, adding that it was “very important” to understand how many human infections are occuring “because that’s where adaptation [of the virus] will happen”. He added: “It’s a tragic thing to say, but if I get infected with H5N1 and I die, that’s the end of it. If I go around the community and I spread it to somebody else then you start the cycle.” He said efforts were being made to develop vaccines and therapeutics for the strain and stressed the importance of international health authorities having the capacity to diagnose the virus.  This would ensure that the world would be “in a position to immediately respond” if the strain “did come across to humans, with human-to-human transmission”, said Dr Farrar. 

Experts warn that lax regulations could also see the virus spread to US pig farms, with serious consequences for human health. Fears are growing that the H5N1 outbreak among cattle in the United States could have been caused by contaminated animal feed.  In contrast to Britain and Europe, American farmers are still allowed to feed cattle and other farm animals ground-up waste from other animals including birds. Dairy cows across six US states – and at least one farm worker – have become infected with the highly pathogenic virus, which has already killed millions of animals across the globe since 2021. The farm worker, who is thought to have been exposed via infected cattle in Texas, is only the second recorded human H5N1 case in the US. Since February, the US has investigated and discounted a further 8,000 possible exposures, according to Dr Joshua Mott, WHO senior advisor on influenza.  The development is of concern because it allows the virus, which has killed millions of birds and wild mammals around the world, more opportunities to mutate...

The Idaho State Department of Agriculture announced that HPAI, known as highly pathogenic avian influenza, or bird flu, has been found in dairy cattle in Idaho.  This now brings the number of affected states to four, adding more evidence the virus may be spreading cow to cow. The cows were recently brought into the Cassia County dairy from another state that had found HPAI in dairy cattle, according to the ISDA. The USDA Animal and Plant Health Inspection Service (APHIS) announced that an investigation into mysterious illnesses in dairy cows in three states—Kansas, New Mexico, and Texas—was due to HPAI and that wild birds are the source of the virus.

Symptoms of HPAI in cattle include: 

• Drop in milk production 
• Loss of appetite 
• Changes in manure consistency 
• Thickened or colostrum-like milk 
• Low-grade fever 

At this stage, there is no concern about the safety of the commercial milk supply or that this circumstance poses a risk to consumer health. The pasteurization process of heating milk to a high temperature ensures milk and dairy products can be consumed safely. 

The ISDA encourages all dairy producers to closely monitor their herd and contact their local veterinarian immediately if cattle appear to show symptoms. HPAI is a mandatory reportable disease, and any Idaho veterinarians who suspect cases of HPAI in livestock should immediately report it to ISDA at 208-332-8540 or complete the HPAI Livestock Screen at agri.idaho.gov/main/animals/hpai/.  

APHIS (USDA) update on the dairy cattle bird flu outbreaks (March 29, 2024):

https://www.aphis.usda.gov/news/agency-announcements/usda-fda-cdc-share-update-hpai-detections-dairy-cattle 

More than 20 of the birds, which are critically endangered, have died in recent months.

The News

Federal officials have granted emergency approval to a bird flu vaccine for use in California condors, an agency of the U.S. Department of Agriculture announced on Tuesday. The move comes after more than a dozen of the birds, which are critically endangered, recently died from the virus, known as H5N1. Worldwide, there are fewer than 600 California condors, which can have wingspans of nearly 10 feet. The emergency approval is “an attempt to prevent additional deaths of these birds,” said the agency, the Animal and Plant Health Inspection Service. The vaccine was initially developed for a different version of avian influenza, and the condors will not begin receiving it right away. Three federal agencies — the Animal and Plant Health Inspection Service, the U.S. Fish and Wildlife Service and the U.S. Geological Survey — are now working together to test the vaccine in black vultures, a species related to California condors. Twenty vultures in North Carolina received the shots on Tuesday, the agencies said in a joint email. If the results are promising, the next step will be to vaccinate 25 captive condors, they said.

Why It Matters: Condors are at high risk.

The virus was first detected in a California condor found dead in late March. Since then, 20 more condors have died and four additional condors are currently in rehabilitation facilities, according to the federal agency. The virus has been confirmed in 15 of those birds. Condors appear to be “highly susceptible” to the virus, said Dr. Carlos Sanchez, the head veterinarian at the Oregon Zoo, which has a condor breeding program. “Once they get it,” he said, “they tend to have high mortality.” California condor populations dropped precipitously during the 20th century; in the 1980s, fewer than 30 birds were left. In the decades since, captive breeding programs have helped the population recover. If the virus gets into more condor populations, it could erase this progress, Dr. Sanchez said: “We’re talking about a potential catastrophic collapse of the conservation project.”

Background: A new version of an old threat.

The H5N1 virus was first detected in China in 1996. Since then, various versions of the virus have circulated in wild birds and caused repeated outbreaks in poultry. A new version of the virus arrived in North America in late 2021. Since then, it has spread rapidly throughout the United States, causing the largest bird flu outbreak in the nation’s history and resulting in the death of almost 60 million farmed birds. It has also taken a far heavier toll on wild birds than previous outbreaks. It has been detected in more than 6,700 wild birds — a figure that is surely an underestimate — in every state but Hawaii and has resulted in mass die-offs of wild birds around the world. It has also repeatedly spilled over into mammals and caused a small number of human infections, generally in people who were known to have been in close contact with birds. The virus is best adapted to birds, and the threat to the general public remains low, officials say. But scientists have long been concerned that the virus could evolve in ways that help it spread easily among people.

What’s next: Officials are considering a broader bird vaccination campaign.

The small size of the existing California condor population will allow the vaccination program to be monitored closely, the Animal and Plant Health Inspection Service said. Federal officials have not authorized the vaccine for use in other birds. But the size and scope of the current outbreak have prompted officials to consider a mass poultry vaccination campaign. U.S.D.A. scientists have been testing numerous potential poultry vaccines and have said that some results could be available this spring. The country could see more animal outbreaks in the coming weeks as infected wild birds migrate north for the summer.

A recent outbreak of avian flu has killed 7 per cent of the wild population of California condors, and officials are bracing for the virus’ spread. At least 20 California condors have died of avian flu in recent weeks, and wildlife officials are preparing for the virus’ spread among the critically endangered birds. The highly contagious H5N1 bird flu that is killing North America’s biggest bird is the same strain that forced farmers to cull millions of chickens over the last year. It is a major blow to the population of California condors (Gymnogyps californianus), which were pushed to the edge of extinction in the 1980s. Intensive breeding and habitat conservation efforts have since bolstered their numbers to around 500 birds, around 300 of which live in the wild. Clusters of the giant vultures can now be found from western Canada down to northern Mexico. Wildfires have drastically reduced lynx habitat in Washington state. In recent weeks, the US Fish and Wildlife Service had confirmed at least 20 condor deaths in a flock located around Arizona and Utah. So far, 10 of the condors in that flock have tested positive for avian flu and the 10 remaining birds are currently undergoing examination.

The deaths represent a 7 per cent loss of the species’ wild population. As of 17 April, the US Fish and Wildlife Service was rehabilitating four condors from the flock in the south-west US. They were “receiving supportive care and have shown improvement”, according to a statement. “My worry is that avian flu could spread throughout the regional condor groups as the disease becomes more prevalent in bird populations in general,” says Ileene Anderson at the Center for Biological Diversity in Arizona. “Since there is no known vaccine or proven treatment, at a minimum it could set back California condor recovery for years and at the worst it could decimate the population.” Avian flu has not been detected in neighbouring flocks in California or Mexico’s Baja California peninsula. Officials say they are monitoring nearby condors and preparing in the event that it spreads, especially as migratory birds that could ferry the virus fly north for spring migration. Though there have been rare cases of avian flu illness and deaths in humans, public health officials say that transmission is rare and advise avoiding close contact with sick or dead wildlife.

Three domestic cats in the U.S. – two in Nebraska and one in Wyoming – have recently tested positive for H5N1 avian influenza after eating wild birds, scientists say. A dog in Canada died of bird flu last week. In Wyoming, the State Veterinary Laboratory said in a brief statement that a barn cat tested positive for bird flu near Thermopolis, a small town in Hot Springs County, about 110 miles southeast of Casper. “This is the first report of HPAI (highly pathogenic avian influenza) in a domestic cat in Wyoming, and it likely became infected from ingesting meat from wild waterfowl,” the lab’s statement said. There was no information about the cat’s condition, but Dr. Myrna Miller, the lab’s supervisor of virology, said several semi-feral cats and skunks were recently found dead at or near the ranch. The other animals have not been tested After a previous version of this article was published on Thursday night, Dr. Miller informed BNO News about a recent case in Nebraska where two domestic cats had also tested positive for H5N1.

Dr. Sarah Sillman, from the University of Nebraska’s Veterinary Diagnostic Center, wrote in a case report that two domestic cats died in January after being infected with bird flu, presumably from predation of wild birds. The first cat in Nebraska died after experiencing a “rapid decline” in health with multiple symptoms, including weight loss, fever, seizures, tremors and loss of proprioception. “The PCR Ct value for avian influenza in the brain of this cat was remarkably low (12), indicating a very large amount of virus in the brain, as consistent with an acute infection,” Dr. Sillman wrote. Three other cats in the household were considered to be at risk of bird flu and one of them developed symptoms shortly after the first affected cat. “The cat was described as somnolent and had episodes of walking in circles,” Dr. Sillman wrote. “The cat was responsive to stimuli and seemed to eat and drink normally. It lived 10 days with neurologic impairment, when the cat suddenly became laterally recumbent with continual tremors, necessitating euthanasia.” A necropsy found major lesions only in the brain of the second cat and a test was positive for H5N1, Dr. Sillman said. The other two cats in the household did not develop symptoms and both tested negative for the virus.

“It is presumed that the two cats described here became infected from predation of wild birds infected with the virus given the circumstances of the case,” Dr. Sillman said. “Keeping cats indoors to prevent wild bird contact – particularly given the context of the current HPAI outbreak – and avoiding feeding uncooked poultry are recommendations to minimize risk of H5N1 infection.” It’s believed to be the first time that cats in the U.S. have been infected with the new strain of H5N1, which emerged in late 2021. In December, a cat living near a duck farm in southern France also tested positive for H5N1. The cat became severely ill and had to be euthanised. Earlier this week, the Canadian Public Health Agency confirmed that a dog in Ontario had died of H5N1 after chewing on a dead goose. It was the first time a dog tested positive for the new strain of the virus. In addition to the cat, Wyoming also reported that four mountain lions and a fox have recently died of bird flu. The global spread of H5N1 clade 2.3.4.4b – and the recent spread to a growing number of mammals – has raised concern about the possibility of a future variant which could lead to human-to-human transmission. So far, only a few human cases have been found after contact with infected birds. “The global H5N1 situation is worrying given the wide spread of the virus in birds around the world and the increasing reports of cases in mammals, including in humans,” Dr. Sylvie Briand, a WHO official, said on February 24. “WHO takes the risk from this virus seriously and urges heightened vigilance from all countries.”