{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
____
No comments:
Post a Comment