Estimating the #time of Highly Pathogenic Avian #Influenza virus #introduction into #USA #poultry flocks during the 2022/24 #epizootic

Abstract

Following confirmation of the first case of the ongoing U.S. HPAI H5N1 epizootic in commercial poultry on February 8, 2022, the virus has continued to devastate the U.S. poultry sector and the pathogen has since managed to cross over to livestock and a few human cases have also been reported. Efficient outbreak management benefits greatly from timely detection and proper identification of the pathways of virus introduction and spread. In this study, we used changes in mortality rates as a proxy for HPAI incidence in a layer, broiler and turkey flock together with diagnostic test results to infer within-flock HPAI transmission dynamics. Mathematical modeling techniques, specifically the Approximate Bayesian Computation algorithm in conjunction with a stochastic within-flock HPAI transmission model were used in the analysis. The time window of HPAI virus introduction into the flock (TOI) and the adequate contact rate (ACR) were estimated. Then, using the estimated TOI together with the day when the first HPAI positive sample was collected from the flock, we calculated the most likely time to first positive sample (MTFPS) which reflects the time to HPAI detection. The estimated joint (i.e., all species combined) median of the MTFPS for different flocks was six days, the joint median most likely ACR was 6.8 newly infected birds per infectious bird per day, the joint median R0 was 13 and the joint median number of test days per flock was two. These results were also grouped by species and by epidemic phase and discussed accordingly. We conclude that this findings from this and other related studies are beneficial for the different stakeholders in outbreak management. We recommend that combining TOI analysis with complementary approaches such as phylogenetic analyses is critically important for improved understanding of disease transmission pathways. The estimated parameters can also be used to parametrize mathematical models that can guide the design of surveillance protocols, risk analyses of HPAI spread, and emergency preparedness for HPAI outbreaks.

Source: PLOS One, LINK

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#USA, First #Hawaii #Pediatric #Influenza-Associated #Death of the 2024-2025 Season Recorded

 {Excerpt}

HONOLULU — The Hawaiʻi Department of Health (DOH) announced today the first influenza-associated death in a Hawaiʻi resident under the age of 18 during this influenza, or flu season. 

This child was a Hawaiʻi County resident with underlying medical conditions. 

While specimens were not available for subtyping beyond the positive influenza result, medical and exposure history pointed to seasonal influenza as the most likely cause of illness. 

This case is not believed to be associated with the recent wastewater detection of H5 in Hilo. 

Out of respect for the family’s privacy, no further information about the child is being released.

“It is always a tragedy to lose any life, and we all feel it even more deeply when it is one of our keiki,” said DOH Director Dr. Kenneth Fink. “Seasonal influenza remains a significant health concern. If you or your loved ones have not received the flu vaccine this season, I hope you will consider doing so to help protect your ʻohana and those around you, particularly with gatherings during the holiday season.”

(...)

Source: Department of Health, LINK

#USA, Confirmed #human #H5N1 case #summary during 2024 #outbreak, by state and exposure source: 2 new cases, total = 60 (as of Dec. 13 '24)

 Source: US Centers for Disease Control and Prevention, LINK <||> 

{Excerpt}

Exposure Source

{State - Cattle - Poultry - Unknown - State Total}

1) California - 33 - 0 - 1 - 34 {+2}

2) Colorado - 1 - 9 - 0 - 10

3) Michigan - 2 - 0 - 0 - 2

4) Missouri - 0 - 0 - 1 - 1 

5) Oregon - 0 - 1 - 0 - 1 

6) Texas - 1 - 0 - 0 - 1

7) Washington - 0 - 11 - 0 - 11 

-- Source Total - 37 - 21 - 2 - 60 

NOTE: One additional case was previously detected in a poultry worker in Colorado in 2022.

Additional cases meeting the Council of State and Territorial Epidemiologists (CSTE) probable case definition have been reported by states: 1 case with dairy cow exposure (CA), 3 cases with poultry exposure (WA), and 2 cases with poultry exposure (AZ) and 1 case with no defined exposure (DE). Confirmatory testing at CDC for these cases was negative.

This table is typically updated by 5 PM EST on Mondays (for cases confirmed by CDC on Friday, Saturday, or Sunday), Wednesdays (for cases confirmed by CDC on Monday or Tuesday), and Fridays (for cases confirmed by CDC on Wednesday and Thursday). Affected states may report cases more frequently.

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#USA, LDH detects first presumptive positive #human #H5N1 case in #Louisiana

 Source: Department of Health, LINK <||>

{Excerpt}

December 13, 2024

The Louisiana Department of Health (LDH) has detected the first presumptive positive human case of highly pathogenic avian influenza (HPAI), or H5N1, in Louisiana. The individual is a resident of southwestern Louisiana and is currently hospitalized. 

LDH's Office of Public Health is coordinating with the Centers for Disease Control and Prevention (CDC) on the epidemiologic investigation. The investigation identified that the individual had exposure to sick and dead birds that are suspected to have been infected with H5N1.

H5N1 is a type of influenza virus that causes highly infectious and severe respiratory disease in birds. In the United States, outbreaks of the currently circulating H5N1 avian influenza viruses in wild birds and poultry have been ongoing since 2022. As of December 13, 2024, 60 confirmed human cases of H5N1 have been reported across the U.S., with the majority linked to exposure to infected poultry or dairy cows. There has been no human-to-human virus transmission in the U.S. to date.

While the current public health risk for the general public is low, people who work with birds, poultry or cows, or have recreational exposure to them, are at higher risk.

The best way to protect yourself and your family from H5N1 is to avoid sources of exposure. That means avoiding direct contact with wild birds and other animals infected with or suspected to be infected with bird flu viruses.

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#USA, #California: Current #H5N1 #Birdflu #Situation in #Humans: Two new cases, total now = 34

 Source: Department of Health, LINK <||>

{Excerpt}

Updated December 13, 2024​ 

* ​​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​: 34 {+2} 

​These numbers were last updated on December 13, 2024.

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​​​​: 33

* ​Poultry: ​0

* ​Unkn​own: ​1

* ​Total: ​34

(...)

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#Estimates of #epidemiological #parameters for #H5N1 #influenza in #humans: a rapid review

 Source: MedRxIV, LINK <||> 

Abstract

Background 

The ongoing H5N1 panzootic in mammals has amplified zoonotic pathways to facilitate human infection. Characterising key epidemiological parameters for H5N1 is critical should this become widespread. 

Aim 

To identify and estimate critical epidemiological parameters for H5N1 from past and current outbreaks, and to compare their characteristics with human influenza subtypes. 

Methods 

We searched PubMed, Embase, and Cochrane Library for systematic reviews reporting parameter estimates from primary data or meta-analyses. To address gaps, we searched Google Scholar for studies of any design providing relevant estimates. We estimated the basic reproduction number for the outbreak in the US and estimated the serial interval using data from previous household clusters in Indonesia. We also applied a branching process model to simulate transmission chain size and duration to assess if simulated transmission patterns align with observed dynamics. 

Results 

From 32 studies, we identified H5N1s epidemiological profile as having lower transmissibility (R0 < 0.2) but higher severity compared to human subtypes. Evidence suggests H5N1 has longer incubation (~4 days vs ~2 days) and serial intervals (~6 days vs ~3 days) than human subtypes, impacting transmission dynamics. Key gaps remain regarding latent and infectious periods. 

Conclusions 

We characterised critical epidemiological parameters for H5N1 infection. The current U.S. outbreak shows lower pathogenicity but similar transmissibility compared to prior outbreaks. Longer incubation and serial intervals may enhance contact tracing feasibility. These estimates offer a baseline for monitoring changes in H5N1 epidemiology.

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#USA, #CDC: Novel #Influenza A Virus Cases Report, as of Dec. 13 '24

 Source: US Centers for Disease Control and Prevention, LINK <||>

{Excerpt}

Two probable cases of influenza A(H5) virus infection were reported to CDC this week by the Arizona Department of Health Services. To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States.

These cases occurred among two adult workers, ≥ 18 years of age, performing depopulation activities at a commercial poultry facility where highly pathogenic avian influenza (HPAI) A(H5N1) virus had been detected. While being monitored by local public health, these patients developed illness during the weeks ending November 23 and November 30, respectively. Both patients reported respiratory symptoms. One patient also reported conjunctivitis.

Specimens were collected from the patients and initially tested positive with high CT values at public health laboratories using the CDC influenza A(H5) assay. The specimens were negative for influenza A(H5) virus using diagnostic RT-PCR at CDC. These two probable cases are the first reported human influenza A(H5) cases reported in Arizona. 

No additional notification to WHO of these probable cases is required 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 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.

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#USA, Monitoring for Avian #Influenza A(#H5) Virus In #Wastewater

 Source: US Centers for Disease Control and Prevention, LINK <||>

{Excerpt}

Time Period: December 01 - December 07, 2024

H5 Detection: 60 sites (18.9%)

No Detection: 257 sites (81.1%)

No samples in last week: 14 sites

#Germany - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 Source: WOAH, LINK <||>

Wild birds of different species in Baden-Württemberg.

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Systematic #Review of Avian #Influenza Virus #Infection and #Outcomes during #Pregnancy

 Source: US National Library of Medicine, https://pubmed.ncbi.nlm.nih.gov/39668388/ 

Abstract

Human cases of avian influenza A(H5N2) and A(H5N1) viruses associated with outbreaks in birds and mammals are increasing globally, raising concerns about the possibility of a future avian influenza pandemic. We conducted a systematic review examining 30 reported cases of avian influenza in pregnant women. We found high mortality rates for mothers (90.0%, 27/30) and their babies (86.7%, 26/30) when women were infected with avian influenza virus during pregnancy. Despite being a high-risk population and having worse health outcomes across multiple pandemics, pregnant women are often excluded from vaccine trials. However, as the risk for a new pandemic increases and human vaccines against avian influenza are developed, early inclusion of pregnant women in clinical trials can inform the risk-benefit analysis for both the mother and their newborn infant. Early inclusion of pregnant women in public health vaccination programs is vital for protecting this high-risk population.

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Rapid #Surge of #Reassortant A(#H1N1) #Influenza Viruses in Danish #Swine and their #Zoonotic Potential

 Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2024.12.11.627926v1?rss=1 

Abstract

In 2018, a single detection of a novel reassortant swine influenza A virus (swIAV) was made in Denmark. The hemagglutinin (HA) of the virus was from the H1N1 pandemic 2009 (H1N1pdm09) lineage and the neuraminidase (NA) from the H1N1 Eurasian avian-like swine lineage (H1N1av). By 2022, the novel reassortant virus (H1pdm09N1av) constituted 27 % of swIAVs identified through the Danish passive swIAV surveillance program. Sequencing detected two H1pdm09N1av genotypes; Genotype 1 contained an internal gene cassette of H1N1pdm09 origin, Genotype 2 differed by carrying an NS gene segment of H1N1av origin. The internal gene cassette of Genotype 2 became increasingly dominant, not only in the H1pdm09N1av population, but also in other Danish enzootic swIAV subtypes. Phylogenetic analysis of the HA genes from H1pdm09N1av viruses revealed a monophyletic source, a higher substitution rate compared to other H1N1pdm09 viruses and genetic differences with human seasonal and other swine adapted H1N1pdm09 viruses. Correspondingly, H1pdm09N1av viruses were antigenically distinct from human H1N1pdm09 vaccine viruses. Both H1pdm09N1av genotypes transmitted between ferrets by direct contact, but only Genotype 1 was capable of efficient aerosol transmission. The rapid spread of H1pdm09N1av viruses in Danish swine herds is concerning for swine and human health. Their zoonotic threat is highlighted by the limited pre-existing immunity observed in the human population, aerosol transmission in ferrets and the finding that the internal gene cassette of Genotype 2 was present in the first two zoonotic infections ever detected in Denmark.

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