Yellow Fever - Global Rapid #Risk #Assessment (WHO, June 17 '26, summary)

 

{Summary}

Overall Risk Statement 

    This rapid risk assessment (RRA) aims to assess the overall public health risk at the global level associated with the increase in yellow fever (YF) transmission in the Region of the Americas alongside ongoing YF activity reported in the WHO African Region, documented from the fourth quarter of 2025 through 2026 to date.  

    Together these events involve 13 out of the 40 countries with areas at high risk for YF transmission globally (currently 27 in Africa and 13 in the Americas under the Global Strategy to Eliminate Yellow Fever Epidemics (EYE) classification). 

    For this risk assessment, the WHO Secretariat considered the public health impact of YF, the risk of geographical spread to other WHO regions, and the risk associated with insufficient control capacities. 

    This RRA also provides an assessment of the overall risk in regions with a history of YF transmission, and other regions where the primary vector for urban YF transmission (Aedes aegypti) is present. 

    The overall public health risk also incorporates differences in vaccination status and the availability of epidemiological evidence of YF or arboviral circulation. 

    Unvaccinated populations in at-risk areas constitute the highest risk group; vaccinated populations in the same areas are considered low risk; and populations in areas with no available evidence of YF or indicative arboviral circulation are classified as low risk, albeit with low confidence due to limited surveillance data. 

    The assessment further integrates seasonal ecological dynamics, recognizing that although YF virus transmission can occur year-round in certain ecological zones, marked intra-annual variability exists. 

    In addition, the RRA assesses the risk to countries who do not have competent vectors, as well as the risk to travellers, considering their YF vaccination status. 

    YF outbreaks must be interpreted within their epidemiological and geographic context, as the dynamics of transmission, population immunity, and public health implications differ markedly between high risk and non- risk areas for YF transmission. 

    In high-risk areas, where the virus circulates continuously and population immunity varies, outbreaks may reflect seasonal patterns, gaps in routine immunization, or fluctuations in vector populations. 

    In contrast, outbreaks occurring in areas with no evidence available for YF—where population immunity is typically low and YF virus is not expected to circulate—raise additional concerns regarding viral introduction, the potential for rapid urban transmission, and the need for immediate vaccination and vector control measures, especially in urban settings, to prevent wider spread. 

    Understanding these contextual differences is essential for interpreting the epidemiology, identifying risk factors for severe disease, and determining the relevance and effectiveness of prevention and control strategies. 

(...)

Source: 

Link: https://www.who.int/publications/m/item/who-rapid-risk-assessment--yellow-fever--global-v.1

____

Emerging and re-emerging vector-borne and other #zoonotic #RNA #viruses: #pathogenesis, #climate-driven dynamics, and strategies for global control

 

Abstract

Vector-borne and other zoonotic RNA viruses provide a significant and growing threat to global health, especially in areas where climate change, urbanization, and population growth facilitate the proliferation of arthropod vectors. This review offers an extensive examination of the biology, epidemiology, and pathogenesis of numerous important viruses, including dengue, Zika, chikungunya, yellow fever, Japanese encephalitis, Crimean–Congo hemorrhagic fever, Nipah, Ebola, and hantaviruses. We underscore how environmental and social factors, particularly increasing temperatures, modified precipitation patterns, and accelerated urbanization, transform vector habitats and spillover dynamics. The article further analyzes host–virus and virus–vector interactions, highlighting mechanisms of immune evasion, neurotropism, and vascular disease. Computational and machine learning models are examined as novel instruments for forecasting outbreaks and developing early warning systems. Finally, a summary of present and prospective control options is provided, covering integrated vector management, Wolbachia-based biological control, vaccinations, and antiviral immunotherapies.

Source: 

Link: https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2026.1755594/full

____

Mapping #global emergence of #pathogens with #epidemic and #pandemic #potential to inform and accelerate pandemic #prevention, #preparedness, readiness and response

 

Abstract

Introduction 

Increasing occurrence of epidemics and pandemics and concurrent emergence of different pathogens calls for multi-sectoral, multi-pathogen preparedness actions. Data on various factors that drive emergence of diverse pathogens can inform evidence-based preparedness by identifying geographies at-risk. When leveraging evidence within a One Health approach, multiple pathogens can be addressed simultaneously, thereby strengthening countries pandemic preparedness efforts. 

Methods 

For seventeen priority pathogens (avian influenza viruses, zoonotic coronaviruses including COVID-19, hemorrhagic fever viruses including Ebola, Henipaviruses, and arboviruses including yellow fever and Zika), we identified global evidence on animal reservoirs, vectors, environmental suitability, and reported human cases. We discriminated geospatially recorded pathogen detections from a background sample and constructed maps using these datasets to generate an evidence-based assessment of emergence risk globally. 

Results 

Seventeen pathogen-specific assessments were combined into a global composite map. Sub-Saharan Africa and South Asia have evidence supporting emergence risk for the greatest number of pathogens (included areas at-risk of all pathogens) and scored highest when strength-of-evidence weightings were factored. The Americas had the lowest tally of considered pathogens. Environmental suitability analyses received the highest weights, reservoir ranges the lowest. 

Discussion 

Preparedness and readiness must consider the range of global biological threats. Our methodology is capable of incorporating changing evidence on emergence potential for multiple pathogens to identify geographies at higher risk with different pathogen combinations. Our maps can contribute to existing decision-support structures, guiding shared interventions and strategic allocation of resources for spillover prevention and pandemic preparedness, thereby enhancing local response capacities applying a multidisciplinary approach.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This work was concluded in 2024 and supported by the United States Agency for International Development (USAID) before January 22, 2025, the Germany Agency for International Cooperation (GIZ) and the Government of France.

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.03.20.26347940v1

____

Yellow fever - Region of the #Americas (#WHO D.O.N., May 16 '25)

{Summary}

Situation at a glance

From 29 December 2024 and as of 26 April 2025 (with data for Ecuador updated as of 2 May 2025), a total of 212 confirmed human cases of yellow fever, including 85 deaths, have been reported to WHO by five countries in the Region of the Americas (case fatality rate (CFR) 40%). 

The cases have been reported in the Plurinational State of Bolivia, Brazil, Colombia, Ecuador and Peru. 

The 212 confirmed yellow fever cases reported so far in 2025 represent a threefold increase compared to the 61 confirmed cases reported in 2024. 

WHO is supporting affected countries in implementing coordinated actions to respond to the yellow fever cases and outbreaks. 

This includes: 

- enhancing preventive measures, 

- strengthening surveillance and case management, 

- improving risk communication and community engagement, and 

- implementing immunization activities. 

The current yellow fever situation in the Americas is driven by increased sylvatic transmission cycles. 

The occurrence of yellow fever cases outside of the Amazon basin, combined with high fatality, varying vaccination coverage across affected countries, and limited vaccine supply, contributes to the overall classification of yellow fever risk in the Region of the Americas, especially in endemic countries, as high. 

WHO emphasizes the importance of active surveillance, timely laboratory testing, cross-border coordination, and information sharing. 

Vaccination remains the primary means for the prevention and control of yellow fever. 

WHO continues to support countries in expanding vaccination coverage through routine immunization programs and mass vaccination campaigns to enhance population immunity and reduce the risk of outbreaks.

(...)

Source: World Health Organization, https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON570

____