Correlates of Zika Virus Infection Specific IgG in North-Western Province of Zambia: Results from a Population-Based Cross-Sectional Study

IntroductionZambia is undergoing rapid developmental changes particularly in infrastructure. The opening up of new mines in recent years in North-Western province means that mining has become a major occupation for the province. This has resulted in population movement especially from the 'traditional' Copperbelt province, creating a sudden increase in the total population of the province with resultant challenges for the health sector. Sudden population increase has resulted in over-crowding making a suitable environment for disease spread including the arboviruses.Among the emerging infectious diseases, the arboviral diseases group has particularly warranted attention in the global health landscape with its potential for epidemics and its unprecedented spread (1). Despite the significance and increasing public health impact on individuals worldwide, arboviruses remain poorly understood and controlled. While increasingly well characterised in industrialised countries, the epidemiology of the these viruses is a major challenge to developing countries and surveillance often is usually in the form of reports during outbreaks due to the poor population-based surveillance systems (2). The majority of the surveillance systems were designed to detect known pathogens (61.5%), while 19.9% were for both known and unknown pathogens and only a small proportion were designed to detect unknown pathogens (3).The diagnosis of Zika virus infection is based on detection of specific antibodies (4) or virus isolation from animals or mosquitoes which is time consuming; however, rapid diagnostic methods have been developed for the African and Asian strains (5). Several serological surveys have been carried out in Africa and notable among these is the Portuguese Guinea survey which demonstrated frequent antibodies to group B viruses particularly Yellow Fever, Zika and Wesselbrons; a finding similar to previous surveys in the same region (6). Based on serological analyses, flaviviruses were classified into eight antigenic complexes; however, many viruses including the prototype of the group Yellow Fever and many new viruses could not be affiliated to any complex partly due to extensive geographical distribution, diversity of arthropod vector or vertebrate hosts and also confusion in virus nomenclature (7).No information on Zika virus infection has been reported in Zambia. The objective of the study was, thus, to determine the prevalence and correlates for Zika virus infection in North-Western province of Zambia in order to contribute to the body of knowledge on the epidemiology of Zika virus infection in Zambia.MethodsNorth-Western Province borders with Angola in the West and Democratic Republic of Congo (DRC) in the North. North-Western Province was one of Zambia's nine provinces at the time of the survey before the creation of the tenth province. It covers an area of 125,826 km2 and had a population of 695,599 (8).A total of 1,178 Standard Enumeration Areas (SEAs) were demarcated in North-Western province in the eight districts of the province. North-Western province is located in Agro-ecological zone III which is suitable for cultivating rice, cassava, pineapples and bananas (9).Sample sizeThe data was obtained from a survey on Yellow fever. The sample size calculation was based on the assumption that the sero-prevalence for Yellow fever was 7% based on the study conducted by Robinson (10). A Statcal program in Epi Info v6.04 was used to estimate the sample size. After adjusting for 80% response rate, a sample size of 3600 was obtained. The sample size was equally divided into the two provinces and powered to avoid chance findings, that is, 1,800 participants from each province.SamplingA multi-stage sampling technique was used for participants in all districts. Firstly, wards were randomly selected from each constituency. In the second stage of sampling, standard enumeration areas (SEAs) proportional to the ward size were systematically sampled. …