Highly Pathogenic Avian #Influenza #H5N1 Virus #RNA in #Bovine #Semen, #California, #USA, 2024

 

Abstract

Since March 2024, highly pathogenic avian influenza (HPAI) A(H5N1) virus has infected dairy cattle in the United States, prompting concern about novel transmission routes. During an outbreak in California, HPAI H5N1 RNA was detected in an asymptomatic bull’s semen. Although infectious virus was not isolated, semen-associated transmission risks and biosecurity practices remain a concern.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/32/5/25-1639_article

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Rapid #Decline of #Nesting Peregrine #Falcons in the San Francisco Bay Region of #California Synchronous with an #H5N1 #Outbreak

 

Abstract

After rebounding from near extirpation during the organochlorine era, breeding Peregrine Falcons (Falco peregrinus) in California are again facing adversity, this time consistent with an outbreak of a highly pathogenic avian influenza. Following the first detection of the H5N1 variant clade 2.3.4.4b virus in California wild birds in July 2022, we assembled data from long-term monitoring (2000-2025) of peregrine breeding territory occupancy in the broad vicinity of San Francisco Bay to examine possible impacts on falcon populations. Prior to the outbreak, 47 focal breeding territories had shown nearly complete occupancy by pairs (98.5% of 390 site-years), with very few vacancies, single birds in attendance, or subadult pair members. Within 8 mo of the outbreak, occupancy had dropped to 65.1%, and 2 yrs later (2025), only 36.2% of sites remained occupied. An uptick in site-occupancy by single birds also occurred after the outbreak, but it is unclear whether these were survivors or floaters attempting to fill vacant territories where both pair members had perished. The high vacancy rates signaled an impact upon floaters (nonbreeding adults) that normally buffer breeding site-occupancy in healthy peregrine populations. From October 2022 through November 2025, 17 peregrine fatalities were diagnosed with H5N1 within the counties comprising our study area. Evidence that H5N1 caused these territory vacancies includes, (1) the striking temporal coincidence of occupancy loss with the outbreak, and (2) the lethality of the virus to peregrines and its confirmed presence in peregrine prey in our study area. Our study reaffirms the value of long-term territory occupancy monitoring in this sentinel species.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Helen and Will Webster Foundation

Ahmanson Foundation, https://ror.org/01eywvb34

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.02.11.705416v1

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One confirmed and one potential #human case of #influenza #H5N1 detected through an expanded subtyping protocol

 

ABSTRACT

Current U.S. surveillance for highly pathogenic avian influenza A(H5N1) in humans prioritizes individuals with known animal exposures, potentially missing community-acquired infections. To address this gap, we implemented universal H5 subtyping of all influenza A-positive respiratory samples collected within our hospital system, regardless of patient exposure history. Between August 2024 and April 2025, we subtyped 4,488 influenza A-positive samples and identified two cases positive for H5 RNA in Alameda County, California, USA. The first case was a 14-month-old girl with mild respiratory symptoms and no H5N1 exposure risks; sequencing of the sample revealed an H5 gene closely related to clade 2.3.4.4b, genotype B3.13 viruses circulating in U.S. dairies. The second case was a 79-year-old male, also with no known exposures, whose sample reproducibly tested positive with a high cycle threshold value but could not be confirmed by public health laboratories. Both patients had evidence of co-infection with other common respiratory viruses. These findings, while requiring cautious interpretation due to low virus levels and the presence of potential confounding factors, highlight limitations in exposure-based testing and demonstrate the potential for cryptic H5N1 circulation. This report underscores that broader, geographically targeted surveillance may be a critical tool for early detection of potential community transmission of pandemic-capable pathogens.

Source: 

Link: https://journals.asm.org/doi/10.1128/asmcr.00165-25

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#Influenza A Virus detection in Bulk Tank and Pen Level #Milk from #Dairies Affected by Highly Pathogenic Avian Influenza #H5N1

 

Abstract

Highly pathogenic avian influenza virus H5N1 has been infecting dairy herds in the U.S. since its initial incursion into cows in early 2024. Although national strategies have aimed to detect affected herds, the best way to surveil herds for the H5N1 virus has not been formally studied and we also do not understand herd-level patterns of infection. To understand infection patterns of H5N1 in dairy herds over time, we conducted early surveillance of non-affected farms in California in the Fall of 2024 in an observational study. Daily bulk tank milk (BTM) samples were submitted from each herd and tested for influenza A (IAV) via rRt-PCR. In a subset of herds, IAV testing of multiple excretion types from cattle of different classes and pen-level daily milk was also completed soon after BTM detection. Daily detections of IAV occurred in BTM for a minimum of 33 days, with some herds continuing to have detection beyond a 75-day window. BTM Ct nadirs were seen between 1-3 weeks of detection. In herds that were tested, virus was detected in the milk from all pens of cattle within a very short time frame after BTM detection, or prior to the initiation of pen level sampling. A very low percentage (2.8%) of individual cow samples tested positive for IAV when collected soon after BTM detection, and although the virus was found in all excretion types, a majority of positive samples were from milk. This suggests that BTM may be the best early indicator of herd infection, and that movement of the virus to all lactating pens of cattle after herd incursion is relatively quick. These results also suggest that surveillance strategies with a long interval between BTM testing days may miss herds with short infection windows. Because most herds experienced test days where some submitted BTM samples had virus detected while others did not, and virus was detected in pen level milk samples when the BTM from the herd had become test negative, this work also highlights the necessity of studying the test sensitivity of IAV rRt-PCR detection in aggregate milk samples.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This project was completed using Federal funds provided through the United States Department of Agriculture, Cooperative Agreement 25-9419-0731 and the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under Contract No. 75N93021C00016.

Source: MedRxIV, https://www.medrxiv.org/content/10.1101/2025.10.26.25338833v1

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Unexpected #Detection of Highly Pathogenic Avian #Influenza (HPAI) #H5N1 virus in #bovine #Semen

 

Abstract

Since March 2024, HPAI H5N1 virus has infected dairy cattle in the U.S., prompting concern about novel transmission routes. During an outbreak in California, HPAI H5N1 RNA was detected in an asymptomatic bull's semen. Although infectious virus was not isolated, questions remain about semen-associated transmission risks and biosecurity practices.

Competing Interest Statement

The authors have declared no competing interest.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.10.16.682947v1

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Highly Pathogenic Avian #Influenza #H5N1 Virus #Infection in a #Child with No Known Exposure — San Francisco, #California, December 2024–January 2025

 

Summary

-- What is already known about this topic?

- As of January 1, 2025, 37 human cases of highly pathogenic avian influenza (HPAI) A(H5N1) had been detected in California, none of which occurred in San Francisco.

-- What is added by this report?

- On January 9, 2025, a case of HPAI A(H5N1) infection was identified in a school-aged child in San Francisco through enhanced surveillance (influenza A virus subtyping of a sample of specimens weekly). No source of exposure was identified, and investigations found no laboratory evidence of human-to-human transmission among close contacts.

-- What are the implications for public health practice?

- Enhanced surveillance and timely subtyping of a subset of influenza A–positive specimens, including specimens from persons without known A(H5N1) exposure, are important to detect avian influenza A virus infections. Public health investigations are critical to monitoring for human-to-human transmission.

Abstract

In response to a highly pathogenic avian influenza (HPAI) A(H5N1) outbreak in U.S. dairy cows detected in March 2024, with subsequent identification of human cases, the San Francisco Department of Public Health instituted enhanced influenza surveillance (influenza A virus subtyping of a sample of specimens weekly) in June 2024. As of January 1, 2025, 37 human cases of influenza A(H5N1) had been detected in California, none of which occurred in San Francisco. On January 9, 2025, enhanced surveillance detected a human influenza A(H5N1) virus genotype B3.13 infection in a school-aged child in San Francisco with mild illness. Case investigation and contact tracing were conducted to ascertain exposures and detect possible human-to-human transmission. Activities comprised a household visit that included an environmental assessment, close contact interviews and surveys, and molecular and serologic testing. Sixty-seven close contacts (household, school, and health care) were identified. Upper respiratory tract specimens collected from seven asymptomatic household contacts and four symptomatic school contacts all tested negative for influenza virus by real-time reverse transcription–polymerase chain reaction (rRT-PCR). Although antibodies against influenza A(H5N1) were detected in the index patient, serologic testing of a convenience sample of nine close contacts identified no detectable A(H5)-specific antibodies. Despite an extensive investigation, the infection source remains unknown; no human-to-human transmission was identified among close contacts by rRT-PCR and serologic testing. Continued enhanced surveillance and timely subtyping of a subset of influenza A–positive specimens are essential components of a comprehensive strategy to detect human novel influenza A virus infections, including among persons without known exposures to A(H5N1) viruses.

Source: US Centers for Disease Control and Prevention, MMWR, https://www.cdc.gov/mmwr/volumes/74/wr/mm7433a2.htm?s_cid=OS_mm7433a2_e&ACSTrackingID=USCDC_921-DM149891&ACSTrackingLabel=Week%20in%20MMWR%3A%20Vol.%2074%2C%20September%204%2C%202025&deliveryName=USCDC_921-DM149891

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#Surveillance on #California dairy #farms reveals multiple #sources of #H5N1 #transmission

Abstract

Transmission routes of highly pathogenic H5N1 between cows or to humans remain unclear due to limited data from affected dairy farms. We performed extensive air, farm wastewater, and milk sampling on 14 H5N1 positive dairy farms across two different California regions. Virus was detected in the air in milking parlors and from exhaled breath of cows. Infectious H5N1 virus was detected in the air and water streams; sequence analysis revealed viral variants on a farm in these locations. Longitudinal analysis of milk from the individual quarters of cows revealed a high prevalence of subclinical H5N1 positive cows and a heterogeneous distribution of infected quarters that maintained a consistent pattern over time. Our data highlight potential modes of H5N1 transmission on dairy farms.

Competing Interest Statement

SSL and LCM receive funds from Flu Lab and NIH. ASL receives funds from Flu Lab, NIH, and CDC. ASL receives consulting fees and research support from Roche, outside of the submitted work.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.07.31.666798v1

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Potential #impacts of 2.3.4.4b highly pathogenic #H5N1 avian #influenza virus #infection on Snow #Goose (Anser caerulescens) movement #ecology

Abstract

While wild waterfowl are known reservoirs of avian influenza viruses and facilitate the movement of these viruses, there are notable differences in the response to infection across species. This study explored differential responses to infection with highly pathogenic avian influenza in Snow Geese (Anser caerulescens) located in the California Central Valley. Though H5 antibody prevalence was high across years among birds sampled in the winter (75% in both years via hemagglutination inhibition), these values were even higher among birds sampled in summer that failed to migrate (i.e., August 2023 = 100% and August 2024 = 93% via hemagglutination inhibition). Birds that failed to migrate were also generally lighter than birds sampled in the winter and presented notable damage to cerebrum and cerebellum. In December 2022, a single individual positive for infection with H5N1 at the time of sampling indicated reduced movement during the 14 days following sampling but completed spring migration comparably with uninfected conspecifics. However, while no birds were actively infected during sampling and marking in 2023, two marked geese departed for migration late and one did not migrate at all. Additional banded birds marked in August have been reencountered in scenarios ranging from hunter harvest at a different site over a year later to found dead shortly after banding. Our data indicate that Snow Geese infected with HPAI have the potential to express variable outcomes following infection with highly pathogenic H5N1, ranging from rapid recovery within a migratory season to death. These data also suggest that the abnormal failure of some Snow Geese to migrate from the Central Valley is likely driven by HPAI infection.

Source: PLoS One, https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0328149

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Isolation of Highly Pathogenic Avian #Influenza #H5N1 Virus from #Cat #Urine after Raw #Milk Ingestion, #USA

Abstract

In 2024, 3 domestic cats in California, USA consumed raw milk contaminated with highly pathogenic avian influenza A(H5N1) virus. Fever and neurologic signs developed; 2 cats died. The surviving cat’s urine tested positive for H5N1 virus by reverse transcription PCR. Raw dairy products pose a risk to both animal and human health.

Source: US Centers for Disease Control and Prevention, https://wwwnc.cdc.gov/eid/article/31/8/25-0309_article

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#Evidence of #Viremia in Dairy #Cows Naturally Infected with #Influenza A {#H5N1} Virus, #California, #USA

Abstract

We confirmed influenza A virus (IAV) by PCR in serum from 18 cows on 3 affected dairy farms in California, USA. Our findings indicate the presence of viremia and might help explain IAV transmission dynamics and shedding patterns in cows. An understanding of those dynamics could enable development of IAV mitigation strategies.

Source: US Centers for Disease Control and Prevention, https://wwwnc.cdc.gov/eid/article/31/7/25-0134_article

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#Human Cases of Highly Pathogenic Avian #Influenza A(#H5N1) — #California, September–December 2024

Summary

-- What is already known about this topic?

- Persons with occupational exposure to highly pathogenic avian influenza (HPAI) A(H5N1) virus–infected dairy cattle are at increased risk for infection.

-- What is added by this report?

- During September 30–December 24, 2024, a total of 38 persons received a positive test result for HPAI A(H5N1) viruses in California; 37 were dairy farm workers with occupational exposure to sick cows. One, a person aged <18 years with an undetermined exposure, was the first pediatric patient detected with influenza A(H5) infection in the United States.

-- What are the implications for public health practice?

- Public health agencies should investigate influenza-like illness or conjunctivitis in workers with occupational exposure to animals infected with HPAI A(H5N1) virus. Thorough investigations of all human HPAI A(H5N1) virus infections are necessary to identify potential exposure sources, including monitoring the virus for concerning genetic changes that indicate the potential for person-to-person transmission.

Abstract

Persons who work closely with dairy cows, poultry, or other animals with suspected or confirmed infection with highly pathogenic avian influenza (HPAI) A(H5N1) viruses are at increased risk for infection. In September 2024, the California Department of Public Health was notified of the first human case of HPAI A(H5N1) in California through monitoring of workers on farms with infected cows. During September 30–December 24, 2024, a total of 38 persons received positive test results for HPAI A(H5N1) viruses in California; 37 were dairy farm workers with occupational exposure to sick cows, and one was a child aged <18 years with an undetermined exposure, the first pediatric HPAI A(H5N1) case reported in the United States. All patients had mild illness. The identification of cases associated with occupational exposure to HPAI A(H5N1) viruses on dairy farms highlights the continued risk for persons who work with infected animals. The pediatric case was identified through routine surveillance. Given recent increases in the prevalence of HPAI A(H5N1) viruses among some animal populations, public health agencies should continue to investigate cases of HPAI A(H5N1) in humans as part of control measures, pandemic preparedness, to identify concerning genetic changes, and to prevent and detect potential human-to-human transmission of the virus. To date, no human-to-human transmission of HPAI A(H5N1) virus has been identified in the United States.

Source: US Centers for Disease Control and Prevention (MMWR), http://dx.doi.org/10.15585/mmwr.mm7408a1

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#USA, After #Birdflu Detected in Local #Cat, County #Health Officials Say #Pet Owners Should Contact Veterinarian When Their Pets are Sick

Redwood City — State veterinary and health officials have confirmed a case of H5N1 (bird flu) in a domestic stray cat in San Mateo County. 

The infection, which is not related to the recent instance of bird flu in a backyard flock, was found in a stray cat in Half Moon Bay that had been taken in by a family. 

When it showed symptoms, they took it to Peninsula Humane Society, whose veterinarians examined it and requested testing. Lab results confirmed H5N1. 

It is not known how the cat was infected and it was euthanized due to its condition.

Cats may be exposed to bird flu by consuming infected bird, being in environments contaminated with the virus and consuming unpasteurized milk from infected cows or raw food. Inside domestic animals, such as cats and dogs, that go outside are also at risk of infection.​​​​​​​

According to the Centers for Disease Control and Prevention, the risk of cats spreading H5N1 to people is extremely low, though it is possible for cats to spread some strains of bird flu to people.

While there are no human cases of H5N1 related to this case, this detection in a cat highlights the importance of being proactive about preventing the spread of the virus.

Residents whose pets show signs of illness should contact their veterinarian.

Pets infected with H5N1 may experience a loss of appetite, lethargy and fever, along with neurologic signs, including circling, tremors, seizures or blindness. The illness may quickly progress to:

-- Severe depression

-- Discharge from eyes or nose

-- Other respiratory signs, such as rapid shallow breathing, difficulty breathing and sneezing or coughing

-- Pets with severe illness may die.

If a pet is showing signs of illness consistent with bird flu and has been exposed to infected (sick or dead) wild birds or poultry, residents should contact a veterinarian and monitor their own health for signs of fever or infection.

“We all want to make sure our companion animals are healthy and safe from disease,” said Lori Morton-Feazell, San Mateo County’s chief of Animal Control and Licensing. “If your pet is sick, your veterinarian can determine whether it should be tested for bird flu or any other virus or disease.”

(...)

Source: County of San Mateo, https://www.smcgov.org/ceo/news/after-bird-flu-detected-local-cat-county-health-officials-say-pet-owners-should-contact

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#USA - High pathogenicity avian #influenza #H5N9 viruses (#poultry) (Inf. with) - Immediate notification

Highly pathogenic avian influenza (HPAI) H5N9, Eurasian lineage goose/Guangdong clade 2.3.4.4b and HPAI H5N1 clade 2.3.4.4b were confirmed in a commercial duck premises in Merced County, CA. This is the first confirmed case of HPAI H5N9 in poultry in the United States. The USDA Animal and Plant Health Inspection Service (APHIS), in conjunction with State Animal Health and Wildlife Officials, are conducting comprehensive epidemiological investigations and enhanced surveillance in response to the HPAI related events.

Source: WOAH, https://wahis.woah.org/#/in-review/6201

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#USA, Novel #Influenza A #H5N1 Virus: One Pediatric Case in #California {FluView}

 {Excerpt}

One confirmed human infection with influenza A(H5) virus was reported to CDC this week. To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States.

This case was reported by the California Department of Public Health and occurred in a child less than 18 years old with no known contact with influenza A(H5N1) virus-infected animals or humans. The investigation into the source of infection for this case is ongoing, and no human-to-human transmission has been identified.

A specimen from the individual was tested at a public health laboratory using the CDC influenza A(H5) assay before being sent to CDC for further testing. The specimen was positive for influenza A(H5) virus using diagnostic RT-PCR at CDC. Additional analysis including genetic sequencing is underway. In response to this detection, additional case investigation and contact monitoring are being conducted by public health officials in California.

There have now been 38 total confirmed human A(H5) cases and one probable human case of A(H5) case in California. This is the second reported pediatric case in California and in the United States.

Notification to WHO of this case was initiated per International Health Regulations (IHR). More information regarding IHR can be found at http://www.who.int/topics/international_health_regulations/en/.

The CSTE position statement, which includes updated case definitions for confirmed, probable, and suspected cases is available at http://www.cste.org/resource/resmgr/position_statements_files_2023/24-ID-09_Novel_Influenza_A.pdf

An up-to-date human case summary during the outbreak by state and exposure source is available at www.cdc.gov/bird-flu/situation-summary/index.html

Information about avian influenza is available at https://www.cdc.gov/flu/avianflu/index.htm.

Interim recommendations for Prevention, Monitoring, and Public Health Investigations are available at https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html.

The latest case reports on avian influenza outbreaks in wild birds, commercial poultry, backyard or hobbyist flocks, and mammals in the United States are available from the USDA at https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/2022-hpai.

(...)

Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/fluview/surveillance/2025-week-02.html

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#USA, #California: Current #H5N1 #Influenza in #Human #Situation as of January 15 '25: One new case, total = 38

Current Bird Flu Situation

Updated January 15, 2025​

-- ​​​​The current risk to the public remains low.  ​​

-- No person-to-person spread of bird flu has been detected in California. 

-- People rarely get bird flu, but those who interact​ with infected dairy cows, poultry, or wildlife ​have a greater risk of infection.​​

-- Pasteurized milk and dairy products are safe to consume. Pasteurization inactivates the bird flu virus.​​

-- CDPH is working to protect public health related to bird flu. We monitor infection data, evolving science, and the people affected. Our knowledge will change as we learn more. We are committed to reducing the impact to those at highest risk.

Human Cases in Califo​rnia​

-- ​​​​​​​Confirmed Human Cases​:  38 {+1}

​These numbers were last updated on January 15, 2025.

California has 1 additional probable case with dairy cow exposure that meets the  Council of State and Territorial Epidemiologists (CSTE) ​probable case definition (PDF)​. That case tested positive by a local lab and confirmatory testing at CDC was negative.​​

Confirmed human case summary during the 2024 outbreak, by exposure source.

​-- Cattle​​​​: ​36

-- ​Poultry: ​0

-- ​Unkn​own: ​2

--- ​Total: ​38

(...)

Source: Department of Health, https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/Bird-Flu.aspx

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#USA, #California: Presumptive {#Human #H5N1} #Birdflu Case Identified In #SanFrancisco Resident

FOR IMMEDIATE RELEASE: Friday, January 10, 2025 

*** PRESS RELEASE *** 

Contact: SFDPH Media Desk: DPH.Press@sfdph.org 

SAN FRANCISCO – The San Francisco Department of Public Health (SFDPH) announced today that a presumptive case of H5N1 bird flu has been identified in a San Francisco resident. 

The individual is a child who experienced symptoms of fever and conjunctivitis but did not need to be hospitalized and has since fully recovered. 

The risk to the general public remains low as there is currently no evidence of person-to-person transmission. 

SFDPH is encouraging people to avoid direct contact with sick or dead birds, especially wild birds and poultry. 

Wild birds can be infected with bird flu even if they do not look sick. 

If you have found a dead bird, please contact 311. 

In addition, as bird flu continues to spread among U.S. dairy cows, SFDPH strongly recommends that individuals not consume raw milk or raw milk products, including raw cheese. 

“I want to assure everyone in our city that the risk to the general public is low, and there is no current evidence that the virus can be transmitted between people,” said Dr. Grant Colfax, Director of Health. 

“We will continue to investigate this presumptive case, and I am urging all San Franciscans to avoid direct contact with sick or dead birds, especially wild birds and poultry. Also, please avoid unpasteurized dairy products.” 

The presumptive case tested positive for H5N1 at the SFDPH Public Health Laboratory, which performed this testing as part of enhanced surveillance efforts. 

Confirmatory testing will be performed at the Centers for Disease Control and Prevention (CDC). 

The child initially tested for COVID-19, influenza, and RSV based on symptoms and tested positive for influenza A. As part of SFDPH enhanced surveillance, the specimen was subsequently tested for H5N1. 

An initial investigation by SFDPH has not revealed how the child may have contracted H5N1 bird flu. 

The Department is continuing to investigate, including assessing all close contacts. 

Again, the risk to the general public remains low as there is currently no evidence of person-to-person transmission. 

(...) Human infections with bird flu viruses are rare, and no person-to-person transmission has been detected to date in the United States. Symptoms of bird flu in humans include eye redness, coughing, fatigue, fever, and headaches. If you are experiencing these symptoms, please contact your health care provider. 

At this time, bird flu cases in California have been mild without any hospitalizations. 

Additional case information can be found at the California Department of Public Health and CDC websites.

Source: San Francisco Department of Health, https://www.sf.gov/news/presumptive-bird-flu-case-identified-san-francisco-resident

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#Detection of #Hemagglutinin #H5 #influenza A virus #RNA and model of potential inputs in an #urban #California #sewershed

Abstract

In 2024, the highly pathogenic avian influenza A H5N1 caused outbreaks in wild birds, poultry, cows, and other mammals in the United States with 61 human cases also reported by the CDC. Detection of influenza A H5 RNA in wastewater has been previously reported in sewersheds in Texas and North Carolina with nearby impacted dairy herds following the emergence of H5N1 in dairy cows. Here, we conduct retrospective testing of total influenza A and H5 hemagglutinin genes in wastewater as well presenting and applying new assays for detection of H1 and H3 genes across a respiratory virus season in an urban California sewershed from September 2023-May 2024. Total influenza A, H1, and H3 were regularly detected, while H5 was first detected in March. We developed a model that uses Monte Carlo simulations and previously published parameters to estimate numbers of infected people, poultry, wild birds, or liters of H5-contaminated milk required to result in measured H5 concentrations in wastewater. Our findings demonstrate that in this California sewershed, contaminated milk or infected poultry were the most likely sources of H5 to wastewater. We created a publicly available tool to apply the H5 input model in other sewersheds estimate required inputs.

Source: MedRxIV, https://www.medrxiv.org/content/10.1101/2024.12.31.24319823v1

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#USA, Novel #Influenza A #H5N1 Virus: Five New Cases reported in Week 51/2024 {3 in #California, 1 in #Wisconsin, 1 in #Iowa}

{Excerpts}

-- Five confirmed cases of influenza A(H5) were reported to CDC this week. 

-- To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States.

Three of these cases were reported by the California Department of Public Health. The cases occurred in workers aged ≥18 years at commercial dairy cattle farms in an area where highly pathogenic avian influenza (HPAI) A(H5N1) viruses had been detected in cows. The individuals had mild symptoms, which they reported to local health department officials. There have now been 37 total confirmed cases and one probable case in California during the 2024-2025 influenza season.

One case was reported by the Wisconsin Department of Health. This case occurred in an individual aged ≥18 years who worked at a poultry facility where HPAI A(H5N1) virus had been identified in birds. This individual developed respiratory symptoms during Week 50. Specimens were collected from the individual and initially tested at the state public health laboratories using the CDC influenza A(H5) assay before being sent to CDC for further testing. Influenza A(H5) virus was confirmed at CDC. This is the first influenza A(H5) case in Wisconsin.

One case was reported by the Iowa Department of Health and Human Services. This case occurred in an individual aged ≥18 years who worked at a poultry facility where HPAI A(H5N1) virus had been identified in birds. This individual developed conjunctivitis and respiratory symptoms during Week 50. Specimens were collected from the individual and initially tested at the State Hygienic Laboratory at the University of Iowa using the CDC influenza A(H5) assay before being sent to CDC for further testing. Influenza A(H5) virus was confirmed at CDC. This is the first influenza A(H5) case in Iowa.

Notification to WHO of the cases reported by the Wisconsin and Iowa departments of health was initiated per International Health Regulations (IHR). More information regarding IHR can be found at http://www.who.int/topics/international_health_regulations/en/. 

No additional notification to WHO of the cases exposed to dairy cows in California is required per International Health Regulations (IHR).

The CSTE position statement, which includes updated case definitions for confirmed, probable, and suspected cases is available at http://www.cste.org/resource/resmgr/position_statements_files_2023/24-ID-09_Novel_Influenza_A.pdf

An up-to-date human case summary during the 2024 outbreak by state and exposure source is available at www.cdc.gov/bird-flu/situation-summary/index.html

Information about avian influenza is available at https://www.cdc.gov/flu/avianflu/index.htm.

Interim recommendations for Prevention, Monitoring, and Public Health Investigations are available at https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html.

The latest case reports on avian influenza outbreaks in wild birds, commercial poultry, backyard or hobbyist flocks, and mammals in the United States are available from the USDA at https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/2022-hpai.

(...)

Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/fluview/surveillance/2024-week-51.html

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#USA, #Birdflu tightens grip on #California as #human cases rise

 {Excerpts}

SACRAMENTO, the United States -- California's battle against avian influenza A (H5N1) intensified amid spreading infections across dairy farms and a growing number of human infection, including two newly confirmed cases in Stanislaus and Los Angeles counties.

The virus, commonly known as bird flu, has infected 659 of California's 984 dairy operations since August, with one-quarter of these cases emerging in the past month alone, according to California authorities.

The rapid spread through the state's dairy industry prompted Governor Gavin Newsom to declare a state of emergency last week to protect agricultural workers and public health.

(...)

The outbreak's human impact has grown increasingly severe, with California reporting at least 36 confirmed cases -- more than half of the nation's total of 65, according to the latest report by the U.S. Centers for Disease Control (CDC) on Tuesday, though the actual count is likely higher as recent local confirmations may not yet be reflected in federal data.

Two new cases were confirmed Monday in California's Los Angeles County and Stanislaus County. Both individuals were exposed to livestock infected with bird flu at a worksite, and both had mild symptoms and were treated with antiviral medications, according to the two counties' health departments.

Public health officials have been monitoring wastewater across the state, detecting the virus in several Bay Area locations, including San Francisco, Napa, and San José. However, California State Epidemiologist Erica Pan explained to ABC30 that these detections might be primarily due to "residential or other commercial milk dumping down in the sinks."

Although health officials said the risk remains low for the general public, the virus kills 90 percent to 100 percent of infected poultry and about 1 percent to 2 percent of cows. California State Veterinarian Annette M. Jones noted that infected cows may never fully recover.

As the country's largest dairy producing state, California faced a heavy economic toll from the bird flu outbreak. The virus has led to quarantines and increased testing requirements. The authorities said the state is now testing its 1.7 million cows weekly.

California's milk production dropped 9.2 percent in November from the same month last year, the most significant decline recorded, according to the monthly Milk Production Report released by the U.S. Department of Agriculture (USDA) on Dec. 19. Meanwhile, California's reduced output has led to a 1 percent decrease in national milk production, raising concerns over U.S. dairy product availability and costs.

The state's poultry operations have also been hit hard. The California Department of Food and Agriculture reported that 51 commercial poultry operations and nine backyard flocks across the state had been affected.

The virus has also appeared in unexpected places, with Los Angeles County confirming two cases in domestic cats that consumed contaminated raw milk.

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Source: China Daily, https://www.chinadaily.com.cn/a/202412/26/WS676cb951a310f1265a1d503b.html

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#USA, #California: Public #Health Confirms #Human #H5 #Birdflu Case in #LA County

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{December 23 '24}

The Los Angeles County Department of Public Health has confirmed a human case of H5 bird flu in an adult who was exposed to livestock infected with H5 Bird flu at a worksite. 

This is the first human case of H5 bird flu detected in LA County. 

The person had mild symptoms, has been treated with antivirals, and is recovering at home. 

The overall risk of H5 bird flu to the public remains low.

There is currently no evidence of person to person spread of this virus. 

Close contacts of the infected person and other workers exposed at the worksite are being monitored for symptoms and have been offered personal protective equipment, testing and antiviral prophylaxis. 

No additional cases have been identified at this time. 

Public Health is working closely with the Centers for Disease Control and Prevention (CDC) and the California Department of Public Health (CDPH) on the ongoing investigation.

“People rarely get bird flu, but those who interact​ with infected livestock or wildlife ​have a greater risk of infection. This case reminds us to take basic precautions to prevent being exposed,” said Muntu Davis, MD, MPH, Los Angeles County Health Officer. 

“People should avoid unprotected contact with sick or dead animals including cows, poultry, and wild birds; avoid consuming raw or undercooked animal products, such as raw milk; and protect pets and backyard poultry from exposure to wild animals. It is also important for everyone to get the seasonal flu vaccine, which can help prevent severe seasonal flu illness and lower the risk of getting both seasonal and bird flu infections at the same time if exposed.”

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Source: Los Angeles County Public Health Department, http://publichealth.lacounty.gov/phcommon/public/media/mediapubHPdetail.cfm?cur=cur&prid=4915&row=25&start=1

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