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US Confirms First Human Case Of Bird Flu With No Known Animal Trace
Another person has fallen ill with bird flu in the United States, but this time, public health officials don't know how they caught the highly pathogenic avian influenza virus (HPAIV).
Thankfully, the patient has recovered, but they are the 14th person to fall ill with bird flu in the US this year, and the first patient with "no immediate known animal exposure", according to the Centers for Disease Control and Prevention (CDC).
All previous human cases were among workers who had contracted the virus from sick animals on poultry or dairy farms. This new case is a mystery the CDC is desperately trying to solve.
On August 22, an adult patient tested positive for the avian virus at a hospital in the state of Missouri, where only poultry and wild birds have previously tested positive for the H5N1 strain of the virus.
Initially, the patient tested positive for influenza A, but they didn't match any known human subtype. Further testing revealed the patient had somehow picked up the avian influenza, which is currently spreading among wild and domesticated birds and mammals across the US, as well as Europe, South America, Africa, parts of Asia, and the Antarctic.
This person had no known contact with animals, although it is possible they were exposed to an infected animal without their knowledge.
Officials at the CDC are now sequencing the viral genome of this recent human case to better understand where the pathogen came from and how it might have adapted to infect mammals like ourselves.
The patient in Missouri has not passed the virus on to any close contacts, and without any known case of human to human transmission thus far, the CDC still lists the threat of avian flu to the public as "low".
"The risk of sustained transmission or infection among the general public remains low," confirms the Missouri Department of Health and Senior Services.
The fact that this patient ended up in hospital is a concerning sign, however; it is unknown at this point whether their severe symptoms were due to the virus itself or to underlying medical conditions.
Deputy director of the CDC, Nirav Shah, told The Guardian in an exclusive interview in July that their team is carefully watching for increasing severity of avian flu in humans, as this could indicate the virus is mutating in a way that could be dangerous to public health.
"If we were to see individuals with no connection to a farm whatsoever, or chicken exposure, developing signs and symptoms – that would be greatly concerning," Shah said at the time.
The recent case in Missouri is the first case of bird flu detected as part of the nation's flu surveillance system, under which curious forms of influenza are sent for further testing.
Chinese Farmed Fur Animals Found To Harbor Dozens Of Novel Viruses
Hidden reservoirs: Mink, raccoon dogs, and other fur animals may be breeding grounds for the next pandemic, with newly discovered viruses posing a serious threat to global health.
Study: Farmed fur animals harbour viruses with zoonotic spillover potential. Image Credit: chinahbzyg / Shutterstock
In a recent study published in the journal Nature, researchers conducted a metatranscriptomic investigation of Chinese farmed fur mammals suspected to have died from viral diseases to elucidate if these animals served as a reservoir for viral strains with zoonotic spillover potential. This comprehensive analysis highlights the critical role of fur animals as potential vectors for future pandemics.
Next-generation sequencing of tissues from 461 individual samples collected across 28 species revealed 125 vertebrate-associated virus species from 20 viral families, significantly higher than previously estimated.
Notably, the study identified 36 novel viruses and at least 39 viruses meeting the criteria for high-risk transmission, including seven coronaviruses, depicting cross-species transmission and zoonotic spillover potential. This includes the identification of a novel MERS-like coronavirus in mink and three subtypes of influenza A virus, further expanding the known host range for these pathogens.
The study expanded the known ranges of several virus species and identified previously unknown hosts as disease reservoirs. It highlights mink (reservoir for 23 virus species from 11 viral families), raccoon dogs (19 virus species from 14 viral families), Arctic foxes (13 virus species from 6 viral families), and guinea pigs (potential intermediate host for pathogen transmission) as animals requiring intensive surveillance lest they serve as the trigger for a viral outbreak of pandemic proportions.
Co-infection between different mammalian hosts was observed to be common, with 15 virus species transmitting between fur animals of different orders. For example, the study detected Japanese encephalitis virus in guinea pigs, a virus typically associated with human and swine infections. This finding underscores the broad host spectrum and significant cross-species transmission potential of the identified viruses.
BackgroundDespite the substantial number of human-specific pathogenic viruses in global circulation, most recent disease outbreaks of epidemic or pandemic proportions (Ebola, SARS, MERS, HIV, Lyme disease, Rift Valley fever, Lassa fever, and COVID-19) have resulted from the zoonotic spillover of their causative agents from animals to humans.
The United Nations Environment Program (UNEP) estimates that 60% of known infectious diseases and 75% of emerging infectious diseases originate in animal reservoirs. This highlights the importance of surveillance and research in preventing the next pandemic event.
Modern advances in viral sequencing technologies have enabled high-throughput pathogen screening of farmed animals, arguably the more frequent source of human disease genesis and transmission.
Unfortunately, most research efforts have hitherto focused on conventional livestock (e.G., cows, goats, and swine), with fur animals (e.G., muskrats, mink, and deer) largely overlooked.
Furthermore, most metagenomic investigations of animal viruses use pooled fecal samples (combining multiple individuals from the same species or location), which, while relevant in diversity and evolutionary analyses, fails to unravel prevalence and co-infection processes.
"…fur animals such as foxes, civets and mink have been suggested to be the potential hosts for a variety of human viruses, including influenza A virus (IAV), SARS-CoV and SARS-CoV-2, and outbreaks of H5N1 IAV have recently been reported in farmed European mink. As humans regularly come into contact with farmed animals, it is critical to improve our knowledge of the viruses that circulate among farmed fur animals and their potential for zoonotic transmission."
About the studyThe present study aims to address current knowledge gaps by individually sampling 461 fur animals from across China (a region historically associated with zoonotic outbreaks yet hitherto understudied) to elucidate animal species at heightened risk of serving as viral reservoirs, thereby guiding future surveillance efforts.
Species were categorized as 'main' fur animals (those only farmed for fur and not for food; n = 164 samples from 4 species) and 'multipurpose' farmed animals (n = 297 samples from 24 species). Sample collection was carried out between 2021 and 2024 on dead fur mammals suspected of dying from disease.
Sample tissue collection comprised 441 intestinal, 225 lung, and one liver sample. Mitochondrial cytochrome B (Cytb) confirmed the species of fur animals sampled genetically.
The Illumina NovaSeq 6000 platform was used for RNA sequencing, followed by MEGAHIT (v.1.2.8) for the de novo assembly of the rRNA library. Assembled contigs were passed through a non-redundant protein database (Diamond blastx) to identify viruses within the tissue samples. The Bowtie2 platform was used to estimate viral abundance in each sample (metric = reads mapped per million [RPM]).
"We categorized three types of potentially high-risk viruses: (1) a zoonotic virus was defined as a virus that has been found at least once in humans; (2) a cross-order virus was defined as a virus that has not yet been reported to infect humans, but which has been found in two or more animal orders; and (3) a novel potential risk virus was defined as a virus with >60% amino acid similarity to known viruses, where the genus in question has been found in more than three mammalian orders," the researchers explained.
Study findingsPhylogenetic analysis revealed 125 vertebrate-associated virus species (20 families) across the 461 samples, including 36 previously undescribed species (12 families) absent from the International Committee on Taxonomy of Viruses. Alarmingly, zoonotic viral risk criteria highlighted 13 of these novel species as 'high-risk,' emphasizing the need for further research into their epidemiology.
Three hundred thirty-five host samples (>72%) were found positive for at least one virus species, with the study demonstrating a >60% increase in virus host range over previously known. Most fur animal species investigated were found to play host to between 2 and 23 virus species.
Mink, guinea pigs, raccoon dogs, and Arctic foxes were found to be the most generalist hosts, acting as reservoirs for 23, 20, 19, and 13 virus species, respectively.
Of particular concern is the identification of Pipistrellus bat coronavirus HKU5-like viruses in mink, highlighting a cross-order transmission event with significant zoonotic potential. Additionally, novel influenza A viruses, such as H5N6 and H6N2, were detected in mink and muskrat, respectively, indicating these animals could serve as important intermediate hosts in viral transmission chains.
Co-infection between interspecific mammalian hosts was observed to be commonplace – 15 virus species were found to transmit between fur animals of different orders, 11 of which display the potential for zoonotic transmission to humans.
Together, these findings highlight farmed fur animals as significant reservoirs of potential epi- or pandemic-triggering viral pathogens, underscoring the need for extensive surveillance and research efforts to restrict the transmission of these viromes to humans and other domesticated or wild mammalian populations.
"The order Carnivora carried the highest number of potentially high-risk viruses in this study, while guinea pigs (Rodentia) also carried a high diversity of viruses, including JEV and IAV. Guinea pigs may, therefore, act as intermediate hosts in virus transmission chains and warrant more intensive surveillance," the study concludes.
ConclusionsThe present study identified Chinese farmed fur animals (28 species) as unprecedented reservoirs of more than 125 virus species (20 families), 36 novel to science, and at least 13 categorized as 'high-risk' for their zoonotic transmission potential to humans.
Furthermore, the study revealed high-priority species (e.G., guinea pigs, muskrats, and mink) and frequent co-infections between mammals and humans, highlighting the need for enhanced surveillance and research to avoid and address future zoonotic outbreaks.
The study's findings provide crucial reference data for understanding the potential for fur animals to trigger future outbreaks, emphasizing the importance of ongoing virological surveillance to protect public health.
First Case Of Human Bird Flu Diagnosed Without Exposure To Infected Animals, CDC Says
A patient in Missouri was hospitalized with bird flu despite having no known contact with animals.
The Centers for Disease Control and Prevention (CDC) confirmed the positive case of avian influenza A (H5) on Friday.
The patient, who had underlying medical conditions, was successfully treated with antiviral medications at the hospital and has since been discharged, according to the Missouri Department of Health and Senior Services (DHSS).
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This marks the 14th person (in three states) to contract bird flu in the U.S. This year — and the first infection to occur without any reported exposure to sick or infected animals, the CDC alert stated.
The prior 13 cases came after exposure to dairy cows or poultry.
The CDC has confirmed the positive case of avian influenza A (H5) without any known exposure to animals. (iStock)
Dr. Benjamin Anderson, assistant professor in the Department of Environmental and Global Health at the University of Florida, said the fact that an individual has tested positive for H5 without any reported animal exposure is "very concerning," but noted that very little is known about the case.
"We don't know if the individual had indirect exposure to people or products from agricultural settings," he told Fox News Digital.
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"We also do not yet know the sequence of the virus to determine if it is related to the strains circulating in dairy cattle or not."
A full epidemiological investigation is necessary to determine all potential paths of exposure, Anderson said.
"If our cases of influenza A spike, we need to test more samples to see if some are avian influenza."
"This is definitely something we need to pay very close attention to."
Dr. Edward Liu, chief of infectious diseases at Hackensack Meridian Jersey Shore University Medical Center in New Jersey, echoed the concern about human-to-human spread.
"When that happens, you won't see an animal vector or source," he told Fox News Digital.
A full epidemiological investigation is necessary to determine all potential paths of exposure, said an infectious disease expert. (REUTERS/Dado Ruvic/Illustration/File Photo)
"One of the underlying concerns is that the avian influenza will adapt itself to be more efficient at replicating in humans and better at spreading in respiratory droplets and secretions."
Liu also emphasized that current testing for avian influenza is limited.
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"Knowing it is influenza A doesn't mean it is avian influenza," he said.
"The confirmation of avian influenza requires another step to send it to the state health department or CDC — so we may be measuring the tip of an iceberg. If our cases of influenza A spike, we need to test more samples to see if some are avian influenza."
This marks the 14th person to contract bird flu in the U.S. This year. The prior 13 cases came after exposure to dairy cows or poultry. (iStock)
Dr. Marc Siegel, senior medical analyst for Fox News and clinical professor of medicine at NYU Langone Medical Center, noted that while there hasn't been evidence of animal exposure, "most likely there was."
"There has been no evidence of any human-to-human spread at this point," he told Fox News Digital.
"Surveillance, wastewater analysis and control in animals are key."
The biggest concern for bird flu right now, according to Anderson, is the potential for it to evolve and gain human-to-human transmission ability.
"Influenza viruses can evolve over time through the accumulation of small point mutations in their genetic sequence," he said. "However, they can also evolve very rapidly through what is called recombination — when two or more influenza viruses infecting the same host exchange their genetic material and make a new strain of virus."
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The more this strain of influenza virus circulates, the greater the potential for recombination to occur, the doctor said.
"Right now, the highest-risk human groups are individuals with dairy cow and poultry exposure in areas where spillovers of bird flu have been documented," Anderson said.
Bird flu is not currently in the seasonal influenza vaccine, although the immunization may still provide some protection, one expert said. (iStock)
So far, those who have contracted the dairy cow strain of influenza virus have mostly had mild infections, the doctor noted.
"However, we know these viruses change quickly, so we need to continue to be vigilant in monitoring their circulation."
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Another risk is that avian influenza may cause more severe disease than regular influenza, Liu cautioned.
"It is not currently in our seasonal influenza vaccine, although the vaccine may still provide some protection," he said.
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"Luckily, current prescription antivirals, like Tamiflu, can still treat avian influenza."
As with other flu strains, avian influenza will likely pose a greater risk to older patients, young children, immunocompromised patients, and those with chronic lung, cardiac or kidney disease, the doctor added.
"If it starts to pass from human to human, it could be a huge problem, but we aren't there."
Overall, Siegel said, bird flu poses "no current concern unless it mutates further."
"It needs to be monitored closely," he added. "If it starts to pass from human to human, it could be a huge problem, but we aren't there."
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The CDC stated on Friday that the public risk for bird flu infection remains low.
The agency will continue to investigate the specimen from the human patient, and the Missouri DHSS is looking into potential means of exposure.
Fox News Digital reached out to the Missouri DHSS for comment.
Melissa Rudy is senior health editor and a member of the lifestyle team at Fox News Digital. Story tips can be sent to melissa.Rudy@fox.Com.
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