MRC Centre for Global Infectious Disease Analysis; and the Abdul Latif Jameel Institute for Disease and Emergency Analytics (J-IDEA), School of Public Health, Imperial College London.
J Travel Med. 2021 Apr 14;28(3). doi: 10.1093/jtm/taab015.
There is concern about the risk of yellow fever (YF) establishment in Asia, owing to rising numbers of urban outbreaks in endemic countries and globalisation. Following an outbreak in Angola in 2016, YF cases were introduced into China. Prior to this, YF had never been recorded in Asia, despite climatic suitability and the presence of mosquitoes. An outbreak in Asia could result in widespread fatalities and huge economic impact. Therefore, quantifying the potential risk of YF outbreaks in Asia is a public health priority.
Using international flight data and YF incidence estimates from 2016, we quantified the risk of YF introduction via air travel into Asia. In locations with evidence of a competent mosquito population, the potential for autochthonous YF transmission was estimated using a temperature-dependent model of the reproduction number and a branching process model assuming a negative binomial distribution.
In total, 25 cities across Asia were estimated to be at risk of receiving at least one YF viraemic traveller during 2016. At their average temperatures, we estimated the probability of autochthonous transmission to be <50% in all cities, which was primarily due to the limited number of estimated introductions that year.
Despite the rise in air travel, we found low support for travel patterns between YF endemic countries and Asia resulting in autochthonous transmission during 2016. This supports the historic absence of YF in Asia and suggests it could be due to a limited number of introductions in previous years. Future increases in travel volumes or YF incidence can increase the number of introductions and the risk of autochthonous transmission. Given the high proportion of asymptomatic or mild infections and the challenges of YF surveillance, our model can be used to estimate the introduction and outbreak risk and can provide useful information to surveillance systems.
由于在流行国家的城市暴发数量增加以及全球化的影响，人们对黄热病（YF）在亚洲建立的风险感到担忧。2016 年安哥拉暴发疫情后，YF 病例传入中国。在此之前，尽管气候适宜且存在蚊子，但亚洲从未记录过 YF。亚洲的疫情爆发可能会导致广泛的死亡和巨大的经济影响。因此，量化亚洲 YF 暴发的潜在风险是公共卫生的当务之急。
我们利用国际航班数据和 2016 年的 YF 发病估计数，量化了 YF 通过航空旅行传入亚洲的风险。在有证据表明存在有能力传播病毒的蚊子种群的地方，我们使用繁殖数的温度依赖性模型和假设负二项分布的分支过程模型来估计本地 YF 传播的潜力。
在 2016 年，亚洲共有 25 个城市估计有风险接收至少一名 YF 病毒血症旅行者。根据它们的平均温度，我们估计所有城市的本地传播概率均<50%，这主要是由于当年估计的传入量有限。
尽管航空旅行有所增加，但我们发现，2016 年 YF 流行国家与亚洲之间的旅行模式不太可能导致本地传播。这支持了亚洲历史上没有 YF 的情况，并表明这可能是由于过去几年传入的数量有限。未来旅行量或 YF 发病率的增加会增加传入数量和本地传播的风险。鉴于无症状或轻度感染的比例很高，以及 YF 监测的挑战，我们的模型可用于估计传入和暴发风险，并可为监测系统提供有用的信息。
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