Public Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of Canada, Guelph, ON, Canada.
School of Occupational and Public Health, Ryerson University, Toronto, ON, Canada.
Zoonoses Public Health. 2018 Sep;65(6):595-624. doi: 10.1111/zph.12485. Epub 2018 Jun 17.
Powassan virus (POWV), a flavivirus discovered in 1958, causes sporadic but severe cases of encephalitis in humans. Since 2007, the number of human Powassan cases diagnosed each year in the USA has steadily increased. This is in agreement with predictions that Powassan cases may increase in North America as a result of increased exposure to infected ticks. However, the increase may also reflect improved diagnostics and reporting among other factors.
A scoping review was prioritized to identify and characterize the global literature on POWV. Following an a priori developed protocol, a comprehensive search strategy was implemented. Two reviewers screened titles and abstracts for relevant research and the identified full papers were used to characterize the POWV literature using a predetermined data characterization tool.
One hundred and seventy-eight articles were included. The majority of the studies were conducted in North America (88.2%) between 1958 and 2017. Both genotypes of POWV (Powassan lineage 1 and Deer Tick virus) were isolated or studied in vitro, in vectors, nonhuman hosts and human populations. To date, POWV has been reported in 147 humans in North America. The virus has also been isolated from five tick species, and several animals have tested positive for exposure to the virus. The relevant articles identified in this review cover the following eight topics: epidemiology (123 studies), pathogenesis (66), surveillance (33), virus characterization (22), POWV transmission (8), diagnostic test accuracy (8), treatment (4) and mitigation strategies (3).
The literature on POWV is relatively small compared with other vector-borne diseases, likely because POWV has not been prioritized due to the small number of severe sporadic human cases. With the projected impact of climate change on tick populations, increases in the number of human cases are expected. It is recommended that future research efforts focus on closing some of the important knowledge gaps identified in this scoping review.
波瓦桑病毒（POWV）于 1958 年发现，是一种黄病毒，可导致人类散发性但严重的脑炎。自 2007 年以来，美国每年诊断出的人类波瓦桑病例数量稳步增加。这与预测一致，即由于接触受感染的蜱的机会增加，波瓦桑病例在北美的数量可能会增加。然而，增加也可能反映出诊断和报告的改进等其他因素。
优先进行范围审查，以确定和描述全球有关 POWV 的文献。根据事先制定的方案，实施了全面的搜索策略。两名审查员筛选标题和摘要中与研究相关的内容，并使用预定的数据特征工具来识别和描述确定的全文，以确定 POWV 文献的特征。
共纳入 178 篇文章。大多数研究是在 1958 年至 2017 年间在北美进行的（88.2%）。两种基因型的 POWV（波瓦桑谱系 1 和鹿蜱病毒）均在体外、载体、非人类宿主和人群中分离或进行了研究。迄今为止，北美已有 147 人报告感染了 POWV。该病毒还从五种蜱种中分离出来，并且几种动物对该病毒的暴露呈阳性。本综述中确定的相关文章涵盖以下八个主题：流行病学（123 项研究）、发病机制（66 项）、监测（33 项）、病毒特征（22 项）、POWV 传播（8 项）、诊断试验准确性（8 项）、治疗（4 项）和缓解策略（3 项）。
与其他虫媒病相比，关于 POWV 的文献相对较少，这可能是因为由于严重散发性人类病例数量较少，因此该病毒未被优先考虑。预计气候变化对蜱种群的影响会增加，人类病例的数量也会增加。建议未来的研究工作集中于缩小本范围审查中确定的一些重要知识差距。
