Article Prevalence of Zika and malaria in patients with fever in secondary healthcare facilities in south-eastern Nigeria Akaninyene A Otu 1 , Ubong A Udoh 2 , Okokon I Ita 2 , Joseph P Hicks 3 , Ido Ukpeh 4 and John Walley 5 Abstract We describe the frequency of Zika and malaria among patients presenting with fever to secondary health facilities in Cross River State, Nigeria. Using a cross-sectional, stratified survey design, we randomly selected nine facilities and consecutively recruited 100 participants (aged  1 year) who presented with fever. On testing blood samples using Biocan qualitative lateral flow immuno-chromatographic cassettes for Zika IgG and IgM, 10% were seropositive for Zika virus (ZIKV) IgM, 12% for ZIKV IgG and 20% for ZIKV IgM, IgG or both. Following microscopy of thick films stained with Giemsa for malaria parasites, 55% were positive for malaria and 15% were positive for both malaria and ZIKV IgM, IgG or both. A moderately negative association between urban and rural household location and seropositivity for ZIKV IgM or IgG was found on logistic regression. Our results clearly indicate a high rate of probable ZIKV and malaria co- incidence in Cross River State. Given the high risk of serious fetal outcomes following ZIKV infection, further epidemio- logical research and surveillance systems for ZIKV are clearly required. Keywords Zika, malaria, Cross River, fever Introduction Reaching a diagnosis of febrile illnesses in sub-Saharan Africa remains a dilemma largely owing to the lack of appropriate laboratory testing capacity in many health facilities. Given that up to 92% of the 219 million cases of malaria in 2017 were estimated to occur in Africa, 1 it is not surprising why so many undifferentiated cases of fever in Africa are presumed to be due to malaria and treated with antimalarial drugs. 2 However, arboviral infections such as Zika have been shown to manifest similar symptomatology as malaria. 3 Similarly, infections of the upper respiratory tract, urinary tract and ear will also contribute to the burden of undifferentiated fever. Zika has attracted global public health attention with recent outbreaks in over 50 countries and has been linked to a dramatic rise in the number of cases of microcephaly found in neonates of infected mothers, 4 as well as with fetal death and serious neuro- logical deficits. 5 Zika is a single-stranded RNA flavi- virus which was first isolated in 1947 from a rhesus monkey (Macaca mulatta) in the Zika forest near Lake Victoria, Uganda, 6 and subsequently from the Aedes africanus mosquito in the same forest. Zika virus (ZIKV) is primarily transmitted by the bite of an infected Aedes mosquito although ZIKV has been iso- lated from over 25 species of mosquitoes including Culex. Other modes of transmission of Zika include sexual, 7 perinatal 8 and congenital. 9 Aedes aegypti, 1 Senior Lecturer/Consultant Physician, Department of Internal Medicine, University of Calabar, Calabar, Cross River State, Nigeria 2 Lecturer/Consultant Medical Microbiologist, Department of Medical Microbiology and Parasitology, University of Calabar, Calabar, Cross River State, Nigeria 3 Lecturer in Medical Statistics, Nuffield Centre for International Health, Leeds Institute of Health Sciences, University of Leeds, Leeds, UK 4 Senior Registrar in Internal Medicine, Department of Internal Medicine, University of Calabar, Calabar, Cross River State, Nigeria 5 Clinical Professor of International Public Health, Nuffield Centre of International Health & Development, LIHS, University of Leeds, Leeds, UK Corresponding author: Akaninyene A Otu, Department of Internal Medicine, University of Calabar, Calabar, Cross River State, Nigeria. Email: akanotu@yahoo.com Tropical Doctor 0(0) 1–8 ! The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0049475519872580 journals.sagepub.com/home/tdo