Individual correlates of infectivity of influenza A virus infections in households

Background: Identifying individual correlates of infectivity of influenza virus is important for disease control and prevention. Viral shedding is used as a proxy measure of infectivity in many studies. However, the evidence for this is limited. Methods: In a detailed study of influenza virus transmission within households in 2008–12, we recruited index cases with confirmed influenza infection from outpatient clinics, and followed up their household contacts for 7–10 days to identify secondary infections. We used individual-based hazard models to characterize the relationship between individual viral shedding and individual infectivity. Results: We analyzed 386 households with 1147 household contacts. Index cases were separated into 3 groups according to their estimated level of viral shedding at symptom onset. We did not find a statistically significant association of virus shedding with transmission. Index cases in medium and higher viral shedding groups were estimated to have 21% (95...研究背景：明确与流感病毒感染性相关的个体特征，对于疾病防控具有重要意义。诸多研究中，病毒排毒（viral shedding）常被用作感染性的替代评估指标，但相关实证依据仍较为有限。 研究方法：依托2008至2012年开展的一项针对家庭内流感病毒传播的详细研究，我们从门诊诊所招募经实验室确诊的流感感染患者作为指示病例（index cases），并对其家庭密切接触者进行7至10天的随访，以识别续发感染病例。我们采用基于个体的风险模型（hazard models），以刻画个体病毒排毒水平与个体感染性之间的关联。 研究结果：本研究共纳入386个家庭，涉及1147名家庭密切接触者。研究人员根据指示病例在症状发作时的预估病毒排毒水平，将其划分为3个组别。未发现病毒排毒水平与流感传播存在统计学意义上的显著关联。据估算，病毒排毒水平处于中、高组别的指示病例，其传播风险较对照组高出21%（95...