Zika virus infection in Nicaraguan households

Abstract

Zika virus (ZIKV) infection recently caused major epidemics in the Americas and is linked to congenital birth defects and Guillain-Barré Syndrome. A pilot study of ZIKV infection in Nicaraguan households was conducted from August 31 to October 21, 2016, in Managua, Nicaragua. We enrolled 33 laboratory-confirmed Zika index cases and their household members (109 contacts) and followed them on days 3–4, 6–7, 9–10, and 21, collecting serum/plasma, urine, and saliva specimens along with clinical, demographic, and socio-economic status information. Collected samples were processed by rRT-PCR to determine viral load (VL) and duration of detectable ZIKV RNA in human bodily fluids. At enrollment, 11 (10%) contacts were ZIKV rRT-PCR-positive and 23 (21%) were positive by IgM antibodies; 3 incident cases were detected during the study period. Twenty of 33 (61%) index households had contacts with ZIKV infection, with an average of 1.9 (range 1–6) positive contacts per household, and in 60% of these households, ≥50% of the members were positive for ZIKV infection. Analysis of clinical information allowed us to estimate the symptomatic to asymptomatic (S:A) ratio of 14:23 (1:1.6) among the contacts, finding 62% of the infections to be asymptomatic. The maximum number of days during which ZIKV RNA was detected was 7 days post-symptom onset in saliva and serum/plasma and 22 days in urine. Overall, VL levels in serum/plasma, saliva, and urine specimens were comparable, with means of 5.6, 5.3 and 4.5 log10 copies/ml respectively, with serum attaining the highest VL peak at 8.1 log10 copies/ml. Detecting ZIKV RNA in saliva over a similar time-period and level as in serum/plasma indicates that saliva could potentially serve as a more accessible diagnostic sample. Finding the majority of infections to be asymptomatic emphasizes the importance of silent ZIKV transmission and helps inform public health interventions in the region and globally.

Warming temperatures could expose more than 1.3 billion new people to Zika virus risk by 2050

“…The impacts of the immune history and genetic risk factors of human populations are an additional critical component of the system (Rodriguez-Barraquer et al, 2019). Seroprevalence studies indicate that another catastrophic Zika epidemic is unlikely in LAC in the near term (Netto et al, 2017;Zambrana et al, 2018), but much less is known about ZIKV susceptibility in African, Asian, and Pacific Islander populations. Similarly, microcephaly rates in response to ZIKV infection varied even within the Americas, with the highest rates in Brazil (Johansson et al, 2016) and lower rates in the Caribbean (Francis et al, 2018), suggesting significant variation exists across human populations in the severity of symptoms associated with ZIKV infection.…”

Projecting the end of the Zika virus epidemic in Latin America: a modelling analysis

“…Ferguson et al [ 5 ] developed a model to project when a sufficient number of susceptibles would become available to permit a resurgence of ZIKV, estimating a 25–30 year period. We did not make this type of projection as serological surveys [ 19 , 54 ] published since suggest considerable heterogeneity in exposure within cities and there are variable birth rates across LAC. Both of these factors will add considerable uncertainty to long-term projections for resurgence of ZIKV and is consequently outside of the scope of this analysis.…”

Impact of pre-existing dengue immunity on human antibody and memory B cell responses to Zika

“…PBMCs were obtained between July 2016 and March 2017 from ZIKV-infected patients who were DENV-naïve ( n = 11) or who had previously been exposed to DENV once ( n = 12) or more than once ( n = 8) (Table 1) in the community-based prospective Pediatric Dengue Cohort Study (PDCS) of ~3700 children that has been ongoing since 2004 in Managua, Nicaragua 57 . Blood samples were collected from suspected Zika cases who presented with rash with one or more of the following: conjunctivitis, arthralgia, myalgia, and/or peri-articular edema, regardless of fever 58 . ZIKV infection was confirmed by real-time RT-PCR performed at the National Virology Laboratory of the Ministry of Health in Managua using either of two triplex assays that simultaneously detect ZIKV, CHIKV, and DENV infections: the ZCD assay 5,59 or the CDC Trioplex assay 60 .…”