REVIEW Repetitive dengue outbreaks in East Africa: A proposed phased mitigation approach may reduce its impact Marycelin Baba 1,2 * , Jandouwe Villinger 1 and Daniel K. Masiga 1 1 Martin Lüscher Emerging Infectious Diseases Laboratory (ML-EID), International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya 2 Department of Medical Laboratory Science, P.M.B. 1069, University of Maiduguri, Maiduguri, Nigeria SUMMARY Dengue outbreaks have persistently occurred in eastern African countries for several decades. We assessed each out- break to identify risk factors and propose a framework for prevention and impact mitigation. Seven out of ten countries in eastern Africa and three islands in the Indian Ocean have experienced dengue outbreaks between 1823 and 2014. Major risk factors associated with past dengue outbreaks include climate, virus and vector genetics and human prac- tices. Appropriate use of dengue diagnostic tools and their interpretation are necessary for both outbreak investigations and sero-epidemiological studies. Serosurvey findings during inter-epidemic periods have not been adequately utilised to prevent re-occurrence of dengue outbreaks. Local weather variables may be used to predict dengue outbreaks, while entomological surveillance can complement other disease-mitigation efforts during outbreaks and identify risk-prone areas during inter-epidemic periods. The limitations of past dengue outbreak responses and the enormous socio- economic impacts of the disease on human health are highlighted. Its repeated occurrence in East Africa refutes previ- ous observations that susceptibility may depend on race. Alternate hypotheses on heterotypic protection among flaviviruses may not be applied to all ecologies. Prevention and mitigation of severe dengue outbreaks should necessar- ily consider the diverse factors associated with their occurrence. Implementation of phased dengue mitigation activities can enforce timely and judicious use of scarce resources, promote environmental sanitation, and drive behavioural change, hygienic practices and community-based vector control. Understanding dengue epidemiology and clinical symptoms, as determined by its evolution, are significant to preventing future dengue epidemics. Copyright © 2016 John Wiley & Sons, Ltd. Received: 22 September 2015; Revised: 3 February 2016; Accepted: 4 February 2016 INTRODUCTION Dengue infection is underreported and often misidentified, but its global incidence in 2012 was estimated at almost 400 million in 128 countries in contrast to only nine countries that experienced se- vere dengue epidemics before the 1970s [1,2]. Possibly, many countries (especially in Africa) that experienced dengue outbreaks did not report because of diagnostic limitations. Differential diag- nosis of febrile illnesses for dengue is difficult to attain amidst several endemic diseases (malaria, chikungunya, etc.) with atypical symptoms. Al- though global estimates of dengue infections vary by year, nearly 500000 episodes of dengue haemorrhagic fever (DHF) and dengue shock syn- drome (DSS) occur annually, with over 20 000 dengue-related deaths [2]. The World Health Day campaign focused on dengue in 2014 to emphasise its public health importance [3]. Dengue viruses (DENV) belong to the genus Flavivirus (family: Flaviviridae) and comprise four related serotypes (DENV1-4) with antigenic cross- reactivity, but no cross protection. Sylvatic DENV transmission (between mosquito and monkeys) or extrinsic virus stock being exchanged vertically *Correspondence to: M. Baba, Martin Lüscher Emerging Infectious Diseases Laboratory (ML-EID), International Centre of Insect Physiology and Ecology (icipe), P. O. Box 30772, Nairobi, Kenya. E-mail: marycelinbaba@gmail.com Abbreviations used DF, dengue fever; DHF, dengue haemorrhagic fever; DSS, dengue shock syndrome; DENV, dengue virus; CFR, case fatality rate; YF, Yel- low fever; IgM, Immunoglobulin M; IgG, Immunoglobulin G; PRNT, plaque reduction neutralisation test; MNT, mouse neutralisation test; MCNT, micro neutralisation test; POS, post onset of symptoms; NS1, non-structural protein 1; IEP, inter-epidemic period. Rev. Med. Virol. 2016; 26: 183–196. Published online 29 February 2016 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/rmv.1877 Reviews in Medical Virology Copyright © 2016 John Wiley & Sons, Ltd.