Academic journal article International Public Health Journal

Is North-Western Province of Zambia at Risk for West Nile Virus Infection?

Academic journal article International Public Health Journal

Is North-Western Province of Zambia at Risk for West Nile Virus Infection?

Article excerpt


West Nile virus (WNV) is an arthropod borne virus from the Flaviviridae family. Humans get infected from a culex mosquito bite. Most of the infections are asymptomatic but about 1% show symptoms which sometimes could develop into severe illness (nueroinvasive symptoms) which could also result into death (1).

West Nile fever was first identified in a woman from the west Nile province, Uganda, who presented with influenza like illness in Uganda (2). After the discovery in Uganda the virus became endemic in many African countries, mainly epizootic at that time, with reported seasonal outbreaks in humans (3). The disease was viewed as of very low public health importance till its recognition as an emerging infectious disease as it spread across the globe with reports in Asia, Middle East, Europe and Americas (4-6). In North Africa, a more virulent strain of WNV emerged in 1994 and it caused outbreaks of severe disease symptoms and more deaths than reported previously (5).

Several risk factors for WNV infection emerged from the study in America such as climate and environmental factors. High population density was significantly associated with the viral transmission even after adjusting for other environmental factors (7) and the results were comparable to results obtained in other studies which confirmed an association between urban/sub-urban versus a more rural area (8,9). However other studies reported significant association when there was less population density and rural. Temperature changes determining human activity and mosquito replication was also significantly associated with risk of infection. It was also concluded that these factors could differ yearly due to changes in bird populations with high bird population as being protective (7). It is possible that when there are more birds the virus could be concentrated in bird mosquito bird cycle whereas if there are fewer birds the mosquito could resort to human meals. Studies have also confirmed that age has a bearing on the severity of the infection with the older age group, 50 years and above, being most at risk (7). In Arizon staying at home and not attending school were found to be risk factors to the WNV infection, although it was argued that the possibility that those who stayed at home were the elderly who were already known to be at high risk of infection with WNV (10).

Although WNV infections have been reported worldwide and furthermore around Zambia's neighboring countries, there is still no information on the extent of the problem in the North-western province of Zambia. Therefore the purpose of this analysis was to determine the seroprevalence of WNV and its correlates in North-western province of Zambia.


The study was conducted in North-Western province of Zambia. The province was selected based on the classification as low potential risk areas for yellow fever transmission by World Health Organization (11). North-Western province which borders with Angola on the western side and Democratic Republic of Congo (DRC) on the northern side has a population of 706,462 (12). It is the most sparsely populated province in the country and the provincial capital is Solwezi. The province comprised of 8 districts which were divided into 1178 Standard Enumeration Aras (SEAs) and the main economic activities were mining in one district and general pineapple growing.

Study population, sample size, inclusion/exclusion criteria and sampling

This assessment was carried out among individuals aged nine months or older. In estimating the sample size for persons aged 5 years or older, the following parameters were considered: a prevalence of 7% (13), desired precision or confidence interval (d) of +3%, and a design effect (DE) of 2 and an 80% response rate.

Considering sex, we aimed to recruit 700 male and 700 female participants in each province. Assuming an average of 4 persons aged 5 years or older in each household, a total of 12 households in each of the 30 cluster was to be recruited in the survey. …

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