A Household-Based Study of Contact Networks Relevant for the Spread of Infectious Diseases in the Highlands of Peru

BackgroundFew studies have quantified social mixing in remote rural areas of developing countries, where the burden of infectious diseases is usually the highest. Understanding social mixing patterns in those settings is crucial to inform the implementation of strategies for disease prevention and control. We characterized contact and social mixing patterns in rural communities of the Peruvian highlands.Methods and FindingsThis cross-sectional study was nested in a large prospective household-based study of respiratory infections conducted in the province of San Marcos, Cajamarca-Peru. Members of study households were interviewed using a structured questionnaire of social contacts (conversation or physical interaction) experienced during the last 24 hours. We identified 9015 reported contacts from 588 study household members. The median age of respondents was 17 years (interquartile range [IQR] 4–34 years). The median number of reported contacts was 12 (IQR 8–20) whereas the median number of physical (i.e. skin-to-skin) contacts was 8.5 (IQR 5–14). Study participants had contacts mostly with people of similar age, and with their offspring or parents. The number of reported contacts was mainly determined by the participants’ age, household size and occupation. School-aged children had more contacts than other age groups. Within-household reciprocity of contacts reporting declined with household size (range 70%-100%). Ninety percent of household contact networks were complete, and furthermore, household members' contacts with non-household members showed significant overlap (range 33%-86%), indicating a high degree of contact clustering. A two-level mixing epidemic model was simulated to compare within-household mixing based on observed contact networks and within-household random mixing. No differences in the size or duration of the simulated epidemics were revealed.ConclusionThis study of rural low-density communities in the highlands of Peru suggests contact patterns are highly assortative. Study findings support the use of within-household homogenous mixing assumptions for epidemic modeling in this setting.

背景 目前鲜有研究对传染病负担通常最为沉重的发展中国家偏远农村地区的社交接触模式进行量化分析。明晰此类场景下的社交接触模式，对于指导疾病防控策略的落地实施至关重要。本研究针对秘鲁高地的农村社区，对其接触行为与社交接触模式进行了特征刻画。
方法与结果 本横断面研究（cross-sectional study）嵌套于秘鲁卡哈马卡省圣马科斯省开展的一项大型前瞻性基于家庭的呼吸道感染研究。研究家庭的成员接受了结构化问卷调查，内容为其过去24小时内发生的社交接触（包括交谈或肢体互动）情况。本次研究共从588名研究对象中收集到9015条有效接触报告。研究对象的年龄中位数为17岁（四分位距（interquartile range, IQR）4~34岁）。报告的接触总次数中位数为12次（IQR 8~20次），而肢体接触（即皮肤接触）次数的中位数为8.5次（IQR 5~14次）。研究对象的接触对象多为年龄相近者，以及其子女或父母。报告的接触次数主要受研究对象年龄、家庭规模与职业的影响。学龄儿童的接触次数多于其他年龄组人群。家庭内接触报告的互报率随家庭规模增大而降低（范围70%~100%）。90%的家庭接触网络为完全连通网络，且家庭成员与非家庭成员的接触存在显著重叠（范围33%~86%），表明接触聚集程度较高。本研究构建了双层接触传播流行病模型，用于对比基于实测接触网络的家庭内接触模式与家庭内随机接触模式。模拟得到的流行病规模与持续时长未出现显著差异。
结论 针对秘鲁高地低密度农村社区的本研究表明，其接触模式呈现高度同配性（assortative mixing）。本研究结果支持在该场景下的流行病建模中采用家庭内同质接触假设。