Mechanistic #modelling of highly pathogenic avian #influenza: A scoping #review revealing critical gaps in cross-species #transmission models

 

Abstract

Background

Highly pathogenic avian influenza (HPAI) viruses, particularly subtypes such as H5N1 and H7N9, have caused widespread outbreaks in wild birds, poultry, livestock and occasionally humans, raising concerns about cross-species transmission and pandemic potential. Effective control and surveillance strategies require a thorough understanding of HPAI transmission dynamics, which can be supported by mathematical modelling.

Objective

This scoping review aimed to identify mechanistic models used to study HPAI transmission. Specifically, we sought to categorize model types, describe their application contexts (e.g., wild birds, poultry, livestock, and humans), and highlight modelling gaps relevant to understanding and mitigating the risks of HPAI spread.

Methods

Following PRISMA guidelines and the PRISMA extension for scoping reviews (PRISMA-ScR), we conducted systematic searches of PubMed and Web of Science to identify peer-reviewed studies employing deterministic and stochastic models to analyze HPAI transmission. Eligible articles published between January 2023 and June 2025 were screened and grouped by model structure, host populations, transmission pathways, and modelling objectives.

Results

After screening, 30 studies published after 2023 were included in this scoping review. Compartmental models were the most common (26 studies), with 16 deterministic and 10 stochastic approaches. These models were primarily used to describe transmission among wild birds, poultry, livestock, and humans and to evaluate interventions such as culling, vaccination, and movement restrictions. Agent-based models (2 studies) captured individual-level interactions and spatial heterogeneity, while network models (2 studies) represented contact structures and transmission pathways between farms or species.

Conclusions

Currently, mechanistic modelling of HPAI is dominated by compartmental approaches, including both deterministic and stochastic formulations, whereas agent-based and network models remain relatively underused. Although most studies focus on transmission in wild birds and poultry, and in some cases spillover infections to humans, few explicitly examine infection dynamics in livestock or in transmission between livestock and humans, despite the importance of livestock (e.g., cattle) as potential intermediaries in human infection. Key gaps persist in the integration of empirical data, representation of multi-host interactions, and evaluation of realistic intervention strategies. Addressing these limitations is essential to improve predictive accuracy and to strengthen the role of modelling in informing HPAI surveillance and control.

Source: 

Link: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0347929

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Dual-route #H5N1 #vaccination induces systemic and mucosal #immunity in murine and bovine #models

 

Abstract

Highly pathogenic H5N1 avian influenza (clade 2.3.4.4b) has spread widely among dairy cattle herds since early 2024, causing major economic losses. This zoonotic event emphasizes the urgent need for H5 vaccines eliciting strong, durable, cross-reactive immune responses in cows. To address this, we immunized mice and cattle with a centralized consensus H5 vaccine, localizing near the central node of the human H5 phylogenetic tree. The vaccine was delivered using serotype-switched adenoviral vectors in a prime–boost regimen, combined with intramuscular and intranasal coadministration to target systemic and mucosal immunity and elicit strong humoral and cellular immune responses. This approach strategically integrates multiple innovative features: centralized consensus immunogens, mucosal targeting, and vector serotype switching aimed at maximizing immune protection against H5N1 viruses. Our results show that vaccination elicits strong humoral and cellular immunity in both mice and calves. In challenge experiments, vaccinated mice were fully protected against lethal infection with divergent H5N1 strains, including A/bovine/Ohio/B24OSU-439/2024. Vaccine-induced immunity was consistent across species, supporting the translatability of the mouse model findings to cattle. Overall, our findings represent a promising approach for immunizing key livestock, including cattle, against highly pathogenic avian influenza H5N1, mitigating agricultural losses, and reducing the risk of zoonotic transmission.

Source: 

Link: https://www.nature.com/articles/s41541-026-01460-6

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#Infection of the #bovine mammary #gland by avian #H5N1 subclade 2.3.4.4b #influenza viruses

 

Abstract

The emergence of the panzootic clade of highly pathogenic avian influenza H5N1 (2.3.4.4b) in 2020 marked a major expansion in the host range of influenza A viruses (IAVs), raising concerns about further cross‑species transmission events and zoonotic spillover. Introduction of 2.3.4.4b viruses into U.S. dairy herds has resulted in widespread circulation, accompanied by reduced milk yield, mastitis, and high viral loads in milk. Notably, virus circulation in dairy cattle represents a novel route for mammalian adaptation and transmission that has already led to more than 40 human cases in the U.S. since 2024. Here, we investigated whether avian clade 2.3.4.4b viruses could infect mammary tissue from Aberdeen Angus, Holstein Friesian, and Limousin cattle, three breeds commonly farmed in Europe, the Americas, and Oceania. Using mammary gland explants, we inoculated tissues with attenuated reassortant viruses expressing the haemagglutinin and neuraminidase glycoproteins of three 2.3.4.4b viruses that predated the emergence of H5N1 in US cattle: A/chicken/England/053052/2021 (AIV07), A/chicken/Scotland/054477/2021 (AIV09), and A/chicken/England/085598/2022 (AIV48). Infected epithelial cells were identified using immunohistochemistry in explants from both the teat and gland cistern for all three breeds following infection with AIV09 and AIV48, indicating that mammary tissue from each of the three tested cattle breeds cattle is permissive to H5N1 infection. Lectin staining showed expression of both α2,3‑linked and α2,6‑linked sialic acids in the mammary tissue of all donors showing that all three breeds have the potential to support infection with both avian-adapted and mammalian adapted IAVs. Together, these findings demonstrate that mammary glands from both beef and dairy cattle breeds are permissive to infection with avian‑adapted and mammalian-adapted H5N1 viruses and highlight the potential for this tissue to act as a mixing vessel for IAV reassortment, underscoring the need to include cattle in ongoing H5N1 surveillance and risk‑assessment frameworks.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Medical Research Council, https://ror.org/03x94j517, MR/Y03368X/1, MR/Y03368X/1, MC_UU_0034/2, MC_UU_0034/3, MC_UU_0034/1

Biotechnology and Biological Sciences Research Council, https://ror.org/00cwqg982, BB/V004697/1

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.04.16.718897v1

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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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Serological and viral #prevalence of #Oropouche virus (OROV): A systematic review and meta-analysis from 2000–24 including #human, #animal, and #vector #surveillance studies

 

Abstract

Background

Oropouche virus (OROV) is an emerging arbovirus primarily transmitted by biting midges and is increasingly recognized as a public health threat in Central and South America. With over 11,000 confirmed cases reported in 2024, a ten-fold increase from the previous year, its transmission dynamics and true burden remain poorly understood due to diagnostic challenges and fragmented surveillance systems.

Objective

This systematic review and meta-analysis (SRMA) synthesizes OROV prevalence data in humans and summarizes the available data for vectors and animal hosts sampled between 2000 and 2024 to provide updated estimates and identify key surveillance gaps.

Methods

We systematically searched Web of Science, PubMed, Embase, Medline, and LILACS for OROV seroprevalence and viral prevalence studies in human, insect, and animal populations, published up to September 12, 2024. The review protocol was registered with PROSPERO (CRD42024551000). Studies were extracted in duplicate, and data were meta-analyzed using generalized linear mixed-effects models. Risk of bias was appraised using a modified Joanna Briggs Institute checklist.

Results

We included 71 articles reporting serological or viral prevalence of OROV across nine countries. Between 2000–2024, pooled human seroprevalence among individuals with febrile illness or suspected of Oropouche infection was 12.6% [95% CI 5.3-26.9%] across four South American countries and seroprevalence of 1.1% [95% CI 0.5-2.3%] was observed in asymptomatic groups. Viral prevalence among individuals with febrile illness or suspected of Oropouche infection was 1.5% [0.8-3.0%] across seven South American countries and Haiti. Most studies used convenience sampling and RT-PCR or hemagglutination assays. In vector populations, positive OROV prevalence in Aedes aegypti and Culex quinquefasciatus was reported in two of 18 sources, while 10.0% and 7.5% animal host prevalence was reported in dogs and cattle, respectively. We found high risk of bias in 11.3% of studies in our critical appraisal, with most animal, human, and vector studies falling in the moderate risk of bias range.

Conclusions

Despite rising numbers of OROV reported cases, prevalence estimates remain limited by sparse surveillance and variable methodology. This review highlights the urgent need for standardized serological assays, community-based studies, and expanded surveillance in animal and vector reservoirs. A One Health approach is essential to monitor OROV transmission and inform regional preparedness efforts.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013340

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Joint #FAO / #WHO / #WOAH Rapid #Risk #Assessment of Rift Valley fever (#RVF) in #Senegal and #Mauritania: Implications for Public Health and Animal Health (Oct. 24 '25)

 

{Excerpt}

Risk statement

This risk assessment is based on the current epidemiological and epizootic situation of Rift Valley fever (RVF) in Senegal and Mauritania, from 20 September through 8 October 2025.

The risk assessment was conducted separately for each country. However, the findings indicate that the level of risk is the same for both countries across all levels, for both human and animal health.  

During this period, Senegal reported 119 confirmed human RVF cases, including 16 deaths, resulting in a case fatality rate (CFR) of 13.4%. Cases were recorded across eight health districts in three regions of Senegal, with the majority in Saint-Louis Region with 110 cases (92%) followed by Louga (four cases) and Matam (one case). 

The affected districts in Saint-Louis Region: Podor, Richard-Toll, Dagana, and Saint-Louis are located along the northern border with Mauritania along the Senegal River.  

The most affected age groups were 15- 35 years, accounting for 69 cases (58%), and 35-60 years with 34 cases (29%), with 77 % of cases occurring in males. 

Hemorrhagic symptoms were reported in 22 cases (18%) of which 13 resulted in death.  

Animal infections resulting in abortions and livestock mortality were also reported. 

On 23 September, 1122 blood samples and four abortion samples were collected from small ruminant herds in villages where human cases were reported. 

Of these, 36 samples tested positive across six herds. 

By 30 September, a total of 27 confirmed animal cases, two deaths have been reported to the World Organisation for Animal Health (WOAH) through the World Animal Health Information System (WAHIS). 

As of that date, five animal outbreaks have been confirmed in Saint-Louis Region, with four additional outbreaks expected to be included in a forthcoming follow-up report currently in draft.  

RVF is endemic in Senegal, with previous outbreaks affecting both humans and animals. 

The last confirmed human case before this outbreak occurred in January 2025 in Touba, located in the Diourbel region, while the last recorded human case in Saint-Louis region occurred in 2022.   

Between 27 September and 5 October 2025, Mauritania reported 17 confirmed human RVF cases, including eight deaths, resulting in a CFR of 47%. 

Cases were recorded across seven districts in five regions (wilayas), three of which have international borders: Assaba which borders Mali to the south, Brakna and Trarza both bordering Senegal along the Senegal River. 

Of 66 samples tested, the positivity rate was 25.7%.  

Multiple active outbreaks in animals have also been reported. According to the Ministry of Animal Resources of Mauritania, as of 6 October, 17 outbreaks across eight regions, with 86 out of 307 samples testing positive. 

The first animal cases, involving goats and camels, were reported in August 2025. A total of 39 clinical animal cases (including 16 deaths in two dromedaries and 14 goats) were reported in Aioun, Hodh-Gharbi region and Timbedra, Hodh-Charghi region, both are located in southeastern Mauritania near the Mali border, and in Maghta Lahjar, Brakna region, in central Mauritania.  

In Brakna region alone, 233 animal cases and 55 deaths have been reported to WOAH by 3 October 2025. 

Affected animals include sheep, goats, camels and cattle.  

RVF is endemic in Mauritania. The last major outbreak occurred in 2022, with 47 confirmed human cases, including 23 deaths (CFR 49%), mostly among animal breeders in nine of 15 regions. 

The virus also affected animals such as cattle, camels, and small ruminants, with sample positivity rates of around 24% tested during that outbreak period.  

The current outbreak in Senegal and Mauritania is unusual in both its magnitude and severity. It involves multiple districts in border regions, particularly along the Senegal River, increasing the risk of cross-border transmission between Senegal and Mauritania. 

In Mauritania, the outbreak also extends to eastern regions bordering Mali, raising concerns about potential regional spread beyond the Senegal River basin.  

A notably high proportion of severe and haemorrhagic cases has been reported. In Senegal, 18% of confirmed human cases presented with haemorrhagic symptoms, with 13 cases resulting in death.  

The situation is particularly concerning in Mauritania, where the CFR has reached 47%, reflecting both the severity of illness and potential gaps in early detection and clinical management. 

Further information is needed to better understand the factors contributing to this high fatality rate. 

Possible contributing factors include delayed access to adequate care, shortage of essential medical products and supplies and underreporting of mild cases, which may result in disproportionate detection of severe cases. However, additional factors should also be investigated.  

(...)

Source: World Health Organization, https://www.who.int/publications/m/item/joint-fao-who-woah-rapid-risk-assessment-of-rift-valley-fever-(rvf)-in-senegal-and-mauritania--implications-for-public-health-and-animal-health

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#Detection and #Phylogenetic Characterization of #Influenza D in Swedish #Cattle

Abstract

Increased evidence suggests that cattle are the primary host of Influenza D virus (IDV) and may contribute to respiratory disease in this species. The aim of this study was to detect and characterise IDV in the Swedish cattle population using archived respiratory samples. This retrospective study comprised a collection of a total 1763 samples collected between 1 January 2021 and 30 June 2024. The samples were screened for IDV and other respiratory pathogens using real-time reverse transcription quantitative PCR (rRT-qPCR). Fifty-one IDV-positive samples were identified, with a mean cycle threshold (Ct) value of 27 (range: 15–37). Individual samples with a Ct value of <30 for IDV RNA were further analysed by deep sequencing. Phylogenetic analysis was performed by the maximum likelihood estimation method on the whole IDV genome sequence from 16 samples. The IDV strains collected in 2021 (n = 7) belonged to the D/OK clade, whereas samples from 2023 (n = 4) and 2024 (n = 5) consisted of reassortants between the D/OK and D/660 clades, for the PB2 gene. This study reports the first detection of IDV in Swedish cattle and the circulation of D/OK and reassortant D/OK-D/660 in this population.

Source: Viruses, https://www.mdpi.com/1999-4915/17/1/17

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