Prevalence and Incidence of Zika Virus Infection Among Household Contacts of Patients With Zika Virus Disease, Puerto Rico, 2016–2017

Background Little is known about the prevalence or incidence of Zika virus (ZIKV) infection in settings affected by the 2015–2016 Zika pandemic and associated risk factors. We assessed these factors among household contacts of patients with ZIKV disease enrolled in a cohort study in Puerto Rico during 2016–2017. Methods Household contacts of index case patients completed a questionnaire and gave specimens for real-time polymerase chain reaction (RT-PCR) and immunoglobulin M enzyme-linked immunosorbent assay testing to detect ZIKV infection. We measured the prevalence of ZIKV infection among contacts and associated individual and household factors, examined sexual transmission using a sexual-networks approach, and assessed incident infection among initially uninfected household contacts 2–4 months later. Results Of 366 contacts, 34.4% had evidence of ZIKV infection at enrollment, including 11.2% by RT-PCR. Having open doors and windows that were either screened (prevalence ratio [PR], 2.1 [95% confidence interval {CI}, 1.2–3.6]) or unscreened (PR, 2.5 [95% CI, 1.5–4.1]) was associated with increased prevalence. Sexual partners were more likely to both be RT-PCR positive relative to other relationships (odds ratio, 2.2 [95% CI, 1.1–4.5]). At follow-up, 6.1% of contacts had evidence of incident infection. Conclusions This study identified sexual contact as a risk factor for ZIKV infection. Persons living with ZIKV-infected individuals should be a focus of public health efforts.