背景:2021年8月29日,盟军欢迎行动(OAW)成立,以支持80000多名阿富汗撤离人员在美国的重新安置。在疏散人员中确认麻疹后,进入的撤离航班暂时暂停,并在国内外引入了6个月或6个月以上的撤离人员的大规模麻疹疫苗接种,接种疫苗后21天的隔离期。我们旨在评估这次爆发期间麻疹病毒传播的模式以及控制措施的影响。
方法:我们对作为OAW一部分在美国定居的阿富汗撤离人员进行了麻疹疫情调查。麻疹患者被定义为2021年8月29日至2021年11月26日之间患有急性发热性皮疹疾病的个体,以及实验室确认的感染或与实验室确认的麻疹患者的流行病学联系。我们分析了麻疹患者的人口统计学和临床特征,并使用流行病学信息和全基因组测序来跟踪传播途径。使用传播模型来评估疫苗接种和其他干预措施的效果。
结果:在美国四个州的六个地方,报告了47名麻疹患者(发病率:每1000名撤离人员0·65)。患者的中位年龄为1岁(范围0-26);33(70%)小于5岁。在爆发期间,年龄分布向12个月以下的婴儿转移。20例(43%)野生型麻疹病毒患者在接种疫苗后出现皮疹。没有发现死亡或社区传播,航班恢复后也没有进一步进口。在不干预的情况下,传输模型估计可能发生5506例(IQR10-5626)。基于流行病学标准的感染集群可以使用系统发育分析划分为较小的集群;然而,几乎没有替代计数差异的序列并不总是指示传输的单线。
结论:实施控制措施限制了OAW期间的麻疹传播。我们的发现强调了流行病学和遗传信息之间整合在消除环境中辨别各个传播途径的重要性。
背景:美国疾病控制和预防中心。
On Aug 29, 2021, Operation Allies Welcome (OAW) was established to support the resettlement of more than 80 000 Afghan evacuees in the USA. After identification of measles among evacuees, incoming evacuee flights were temporarily paused, and mass measles vaccination of evacuees aged 6 months or older was introduced domestically and overseas, with a 21-day quarantine period after vaccination. We aimed to evaluate patterns of measles virus transmission during this outbreak and the impact of control measures.
We conducted a measles outbreak investigation among Afghan evacuees who were resettled in the USA as part of OAW. Patients with measles were defined as individuals with an acute febrile rash illness between Aug 29, 2021, and Nov 26, 2021, and either laboratory confirmation of infection or epidemiological link to a patient with measles with laboratory confirmation. We analysed the demographics and clinical characteristics of patients with measles and used epidemiological information and whole-genome sequencing to track transmission pathways. A transmission model was used to evaluate the effects of vaccination and other interventions.
47 people with measles (attack rate: 0·65 per 1000 evacuees) were reported in six US locations housing evacuees in four states. The median age of patients was 1 year (range 0-26); 33 (70%) were younger than 5 years. The age distribution shifted during the outbreak towards infants younger than 12 months. 20 (43%) patients with wild-type measles virus had rash onset after vaccination. No fatalities or community spread were identified, nor further importations after flight resumption. In a non-intervention scenario, transmission models estimated that a median of 5506 cases (IQR 10-5626) could have occurred. Infection clusters based on epidemiological criteria could be delineated into smaller clusters using phylogenetic analyses; however, sequences with few substitution count differences did not always indicate single lines of transmission.
Implementation of control measures limited measles transmission during OAW. Our findings highlight the importance of integration between epidemiological and genetic information in discerning between individual lines of transmission in an elimination setting.
US Centers for Disease Control and Prevention.