Chaw Liling, Kamigaki Taro, Burmaa Alexanderyn, Urtnasan Chuluunbatiin, Od Ishiin, Nyamaa Gunregjaviin, Nymadawa Pagbajabyn, Oshitani Hitoshi
Department of Virology, Tohoku University Graduate School of Medicine, Sendai, Japan.
National Influenza Center, National Center of Communicable Diseases, Ulaanbaatar, Mongolia.
PLoS One. 2016 Feb 5;11(2):e0148421. doi: 10.1371/journal.pone.0148421. eCollection 2016.
Pregnant women and infants under 6 months are at risk of influenza-related complications. Limited information exists on their community burden of respiratory viruses.
This prospective, observational open cohort study was conducted in Baganuur district, Ulaanbaatar, Mongolia during 2013/14 and 2014/15 influenza seasons. Influenza-like illness (ILI) and severe acute respiratory infection (sARI) were identified by follow-up calls twice a week. For those identified, influenza and respiratory syncytical virus (RSV) were tested by point-of-care test kits. We calculated overall and stratified (by trimester or age group) incidence rates (IR) and used Cox proportional hazard regression for risk factor analyses. Among 1260 unvaccinated pregnant women enrolled, overall IRs for ILI, sARI and influenza A were 11.8 (95% confidence interval (C.I):11.2-12.4), 0.1 (95%C.I:0.0-0.4), and 1.7 (95%C.I:1.5-1.9) per 1,000person-days, respectively. One sARI case was influenza A positive. IRs and adjusted hazard ratios (Adj.HR) for ILI and influenza A were lowest in the third trimester. Those with co-morbidity were 1.4 times more likely to develop ILI [Adj.HR:1.4 (95%C.I:1.1-1.9)]. Among 1304 infants enrolled, overall ILI and sARI IRs were 15.2 (95%C.I:14.5-15.8) and 20.5 (95%C.I:19.7-21.3) per 1,000person-days, respectively. From the tested ILI (77.6%) and sARI (30.6%) cases, the overall positivity rates were 6.3% (influenza A), 1.1% (influenza B) and 9.3% (RSV). Positivity rates of influenza A and RSV tend to increase with age. sARI cases were 1.4 times more likely to be male [Adj.HR:1.4 (95%C.I:1.1-1.8)]. Among all influenza A and RSV positive infants, 11.8% and 68.0% were respectively identified among sARI hospitalized cases.
We observed low overall influenza A burden in both groups, though underestimation was likely due to point-of-care tests used. For infants, RSV burden was more significant than influenza A. These findings would be useful for establishing control strategies for both viruses in Mongolia.
孕妇和6个月以下婴儿有发生流感相关并发症的风险。关于其社区呼吸道病毒负担的信息有限。
这项前瞻性、观察性开放队列研究于2013/14年和2014/15年流感季节在蒙古乌兰巴托的巴彦乌勒盖区进行。通过每周两次随访电话来识别流感样疾病（ILI）和严重急性呼吸道感染（sARI）。对于确诊者，使用即时检测试剂盒检测流感和呼吸道合胞病毒（RSV）。我们计算了总体及分层（按孕期或年龄组）发病率（IR），并使用Cox比例风险回归进行危险因素分析。在纳入的1260名未接种疫苗的孕妇中，ILI、sARI和甲型流感的总体发病率分别为每1000人日11.8（95%置信区间（C.I）：11.2 - 12.4）、0.1（95%C.I：0.0 - 0.4）和1.7（95%C.I：1.5 - 1.9）。1例sARI病例甲型流感检测呈阳性。ILI和甲型流感的发病率及调整后风险比（Adj.HR）在孕晚期最低。患有合并症的孕妇发生ILI的可能性高1.4倍[Adj.HR：1.4（95%C.I：1.1 - 1.9）]。在纳入的1304名婴儿中，ILI和sARI的总体发病率分别为每1000人日15.2（95%C.I：14.5 - 15.8）和20.5（95%C.I：19.7 - 21.3）。在检测的ILI病例（77.6%）和sARI病例（30.6%）中，总体阳性率分别为6.3%（甲型流感）、1.1%（乙型流感）和9.3%（RSV）。甲型流感和RSV的阳性率随年龄增长而趋于升高。sARI病例为男性的可能性高1.4倍[Adj.HR：1.4（95%C.I：1.1 - 1.8）]。在所有甲型流感和RSV阳性婴儿中，分别有11.8%和68.0%在sARI住院病例中被确诊。
我们观察到两组中甲型流感的总体负担较低，不过由于使用即时检测，可能存在低估情况。对于婴儿，RSV负担比甲型流感更显著。这些发现将有助于制定蒙古针对这两种病毒的防控策略。
