Hahné Susan, Schurink Tessa, Wallinga Jacco, Kerkhof Jeroen, van der Sande Marianne, van Binnendijk Rob, de Melker Hester
Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), PO Box 1, 3720, BA, Bilthoven, The Netherlands.
BMC Infect Dis. 2017 Jan 10;17(1):56. doi: 10.1186/s12879-016-2135-5.
Mumps emerged among highly vaccinated populations in the Netherlands. This offered a unique opportunity to study mumps virus transmission. In particular the extent to which asymptomatic infections in vaccinated people contribute to ongoing mumps virus transmission is uncertain. Insight into this could help project the future burden of mumps in vaccinated populations. We therefore studied the relative infectiousness of symptomatic and asymptomatic cases.
In a cohort study we followed contacts of notified mumps cases (ring 1) and contacts' contacts (ring 2) for 40 days to ascertain symptoms of mumps and social contacts by weekly diaries and questionnaires, and mumps virus infections by taking finger stick dried blood spot specimens (DBS) that were tested for mumps-specific IgG antibodies. Mumps IgG concentrations >1500 RU/ml in a single sample, a four-fold increase in IgG antibody concentration in paired samples, or a positive oral fluid PCR were defined as recent infection.
We recruited 99 contacts (40 in ring 1 and 59 in ring 2) of 10 mumps index cases. The median age of participants was 23 years (range 18-57 years), 31 (31%) were male. At study entry, DBS of 4 out of 78 (5%) participants with samples showed serological evidence of recent mumps virus infection. Three of these reported mumps symptoms. Among the 59 participants who provided DBS at the beginning and end of the follow-up period, none had serological evidence of infection during this period. Of 72 participants who provided at least one oral fluid sample, one participant (1%) who also reported mumps symptoms, was found PCR positive. Of all 99 participants, the attack rate of self-reported mumps was 4% (95% CI 1.1-10.0%). Of the 5 laboratory confirmed mumps cases, 1 reported no mumps symptoms (percentage asymptomatic 20% (95% CI 0-71%)). Compared to non-students, students had larger households and more household members who were born after 1980 (p < 0.01 and <0.01, respectively).
We demonstrated that this prospective cohort study design allows for inference of the proportion of asymptomatic mumps infections. Because we only detected one asymptomatic mumps virus infection, we could not assess the relative infectiousness of asymptomatic mumps. Household characteristics of students differed from non-students. This may partly explain recent mumps epidemiology in the Netherlands.
荷兰在高疫苗接种率人群中出现了腮腺炎疫情。这为研究腮腺炎病毒传播提供了独特的机会。尤其是接种疫苗人群中的无症状感染对腮腺炎病毒持续传播的影响程度尚不确定。深入了解这一点有助于预测接种疫苗人群未来的腮腺炎负担。因此，我们研究了有症状和无症状病例的相对传染性。
在一项队列研究中，我们对报告的腮腺炎病例的接触者（第1环）及其接触者的接触者（第2环）进行了40天的随访，通过每周的日记和问卷来确定腮腺炎症状和社交接触情况，并通过采集手指刺血干血斑标本（DBS）检测腮腺炎病毒感染，这些标本用于检测腮腺炎特异性IgG抗体。单个样本中腮腺炎IgG浓度>1500 RU/ml、配对样本中IgG抗体浓度增加四倍或口腔液PCR呈阳性被定义为近期感染。
我们招募了10例腮腺炎索引病例的99名接触者（第1环40名，第2环59名）。参与者的中位年龄为23岁（范围18 - 57岁），31名（31%）为男性。在研究开始时，78名提供样本的参与者中有4名（5%）的DBS显示有近期腮腺炎病毒感染的血清学证据。其中3名报告有腮腺炎症状。在随访期开始和结束时提供DBS的59名参与者中，在此期间无人有感染的血清学证据。在提供至少一份口腔液样本的72名参与者中，1名报告有腮腺炎症状的参与者（1%）PCR检测呈阳性。在所有99名参与者中，自我报告的腮腺炎发病率为4%（95%CI 1.1 - 10.0%）。在5例实验室确诊的腮腺炎病例中，1例报告无腮腺炎症状（无症状百分比为20%（95%CI 0 - 71%））。与非学生相比，学生的家庭规模更大，且有更多1980年后出生的家庭成员（分别为p < 0.01和< 0.01）。
我们证明了这种前瞻性队列研究设计能够推断无症状腮腺炎感染的比例。由于我们仅检测到1例无症状腮腺炎病毒感染，所以无法评估无症状腮腺炎的相对传染性。学生的家庭特征与非学生不同。这可能部分解释了荷兰近期的腮腺炎流行病学情况。
