Siraj Amir S, Perkins T Alex
Department of Biological Sciences & Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA.
BMJ Glob Health. 2017 Sep 25;2(3):e000309. doi: 10.1136/bmjgh-2017-000309. eCollection 2017.
On November 18, 2016, the WHO ended its designation of the Zika virus (ZIKV) epidemic as a Public Health Emergency of International Concern (PHEIC). At the same time, ZIKV transmission continues in Asia, with the number of Asian countries reporting Zika cases increasing over the last 2 years. Applying a method that combines epidemiological theory with data on epidemic size and drivers of transmission, we characterised the population at risk of ZIKV infection from mosquitoes in 15 countries in Asia. Projections made under the assumption of no pre-existing immunity suggest that up to 785 (range: 730-992) million people in Asia would be at risk of ZIKV infection under that scenario. Assuming that 20% of ZIKV infections are symptomatic, this implies an upper limit of 146-198 million for the population at risk of a clinical episode of Zika. Due to limited information about pre-existing immunity to ZIKV in the region, we were unable to make specific numerical projections under a more realistic assumption about pre-existing immunity. Even so, combining numerical projections under an assumption of no pre-existing immunity together with theoretical insights about the extent to which pre-existing immunity may lower epidemic size, our results suggest that the population at risk of ZIKV infection in Asia could be even larger than in the Americas. As a result, we conclude that the WHO's removal of the PHEIC designation should not be interpreted as an indication that the threat posed by ZIKV has subsided.
2016年11月18日，世界卫生组织（WHO）不再将寨卡病毒（ZIKV）疫情认定为国际关注的突发公共卫生事件（PHEIC）。与此同时，寨卡病毒在亚洲持续传播，过去两年报告寨卡病例的亚洲国家数量不断增加。我们运用一种将流行病学理论与疫情规模及传播驱动因素数据相结合的方法，对亚洲15个国家中面临蚊虫传播寨卡病毒感染风险的人群进行了特征描述。在假设不存在既往免疫力的情况下所做的预测表明，在这种情况下，亚洲多达7.85亿人（范围：7.30亿 - 9.92亿）有感染寨卡病毒的风险。假设20%的寨卡病毒感染会出现症状，这意味着面临寨卡临床发作风险的人群上限为1.46亿 - 1.98亿。由于该地区关于寨卡病毒既往免疫力的信息有限，我们无法在更符合实际的既往免疫力假设下做出具体的数值预测。即便如此，将不存在既往免疫力假设下的数值预测与关于既往免疫力可能降低疫情规模程度的理论见解相结合，我们的结果表明，亚洲面临寨卡病毒感染风险的人群可能比美洲更大。因此，我们得出结论，WHO取消PHEIC认定不应被解读为寨卡病毒构成的威胁已经消退的迹象。
