Zika virus epidemic: Africa should not be neglected - The Lancet

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Jul 23, 2016 - health agencies (such as African public health institutes and surveillance systems) ... Cape Verde, with 7557 suspected cases between Oct 21 ...
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Zika virus epidemic: Africa should not be neglected The Zika virus was first isolated in Uganda in 1947.1 Despite the recent severe outbreak of Zika virus in Cape Verde, with 7557 suspected cases between Oct 21, 2015, and May 8, 2016, very little attention has been paid to the African continent for participation in Zika virus outbreak preparedness programmes. Since the mid-1950s, findings from seroepidemiological surveys have suggested a high prevalence of Zika virus IgG positivity in western, central, and eastern Africa, with up to 60% people with previous exposure to the virus.2 However, interpretation of these historical results is problematic because of important cross-reactivity of Zika virus serological assays with those of other flaviviruses (eg, dengue viruses), and because of the interference of malaria with modern Zika virus ELISA that results in reduced specificity.3 Aedes aegypti, the main vector of Zika virus, and Aedes albopictus, a convincing alternative candidate, are mainly present in sub-Saharan Africa (figure). Therefore, most of the 936 million inhabitants of the continent (World Bank estimates, 2013) are potentially exposed to Zika virus arthropod vector bites. The incidence and prevalence of microcephaly and Guillain-Barré syndrome, the two main neurological manifestations of Zika virus infection, in Africa are unknown. However, one of the few studies on systematic measurement of head circumference at birth reported a prevalence of microcephaly (according to WHO definition) of 10·6% in more than 3000 consecutive births in Lagos, Nigeria, in 2012.4 Results from a phylogenetic study5 suggested a central role of two African countries, Côte d’Ivoire and Senegal, in the worldwide spread of Zika virus, and that not only the Asian lineage but also the African lineage of the virus might be involved in the spread of Zika virus www.thelancet.com Vol 388 July 23, 2016

Country limits Aedes aegypti Aedes albopictus 0

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Figure: Distribution of Aedes aegypti and Aedes albopictus in Africa

outside of Africa since 2007. However, a comparison of the neurovirulence and neurotropism of African versus Asian strains remains to be reported to improve prediction of potential neurological complications that are attributable to African strains. It is plausible that Zika virus outbreaks occurred in recent years in Africa and remained unnoticed because of the very low capacities for detection of emergent conditions in most of the continent. Surveillance in sentinel populations, increased capacity for laboratory tests and antenatal echography, reporting systems on the emergence of Zika virus-related neurological conditions, intensification of vector control, and education on emerging infectious threats are all of utmost priority in outbreak preparedness programmes. Not long ago, many west African communities were taken by surprise by the Ebola virus epidemic. National and international health organisations

made very strong statements about the importance of learning from the Ebola experience and to improve preparedness for future emergent outbreaks. Now that we know that Zika virus, its vectors, and favourable environmental conditions for their spread are present in Africa, there should be no place for complacency. There is no reason to neglect Africa in international preparedness programmes. Networks of national health agencies (such as African public health institutes and surveillance systems) should be urgently mobilised and empowered to play this crucial part.6

For World Bank estimates see http://www.worldbank.org/en/ about/annual-report/regions/ afr#4

We declare no competing interests.

Nicolas Meda, Sara Salinas, Thérèse Kagoné, Yannick Simonin, *Philippe Van de Perre [email protected] Centre Muraz, Bobo-Dioulasso, Burkina Faso (NM, TK); Pathogenesis and control of chronic infections, UMR 1058 INSERM, University Montpellier, Etablissement Français du Sang, Montpellier, France (SS, YS, PVdP); and Department of Bacterioloy–Virology, CHU Montpellier, Montpellier, France (PVdP)

Submissions should be made via our electronic submission system at http://ees.elsevier.com/ thelancet/

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Dick GWA, Kitchen SF, Haddow AJ. Zika virus. I. Isolations and serological specificity. Trans R Soc Trop Med Hyg 1952; 46: 509–20. Geser A, Henderson BE, Christensen S. A multipurpose serological survey in Kenya. 2. Results of arbovirus serological tests. Bull World Health Organ 1970; 43: 539–52. Van Esbroeck M, Meersman K, Michiels J, Ariën KK, Van den Bossche D. Specificity of Zika virus ELISA: interference with malaria. Euro Surveill 2016; 21: 30237. Olusanya BO. Full-term newborns with congenital microcephaly and macrocephaly in southwest Nigeria. Int Health 2012; 4: 128–34. Shen S, Shi J, Wang J, et al. Phylogenetic analysis revealed the central roles of two African countries in the evolution and worldwide spread of Zika virus. Virol Sin 2016; 31: 118–30. Meda N, Dabis F, Desenclos JC, Crespin X, Delfraissy JF. Network for strong, national, public health institutes in West Africa. Lancet 2016; 387: 2196–97.

Could clinical symptoms be a predictor of complications in Zika virus infection? Compelling evidence of the relation between Zika virus and microcephaly has been emerging in the scientific literature, although the risk in infected pregnant women remains largely unknown. Using retrospective data from routine ultrasonography and clinical examination at birth, Simon Cauchemez and colleagues (May 21, p2125)1 estimated the risk of microcephaly in newborn babies of infected pregnant women at 1% in French Polynesia. Their results differ from those reported in a prospective cohort of 88 pregnant women in Rio de Janeiro presenting with a rash during pregnancy, of whom 72 had Zika virus infection confirmed by RT-PCR.2 Of 42 Zika virus-positive women who had fetal ultrasonography, 12 (29%) had fetal abnormalities, including five fetuses who had intrauterine growth restriction with or without microcephaly. Nine fetuses had some pathological changes in the CNS. The discrepancy between the estimates in the two studies1,2 could be a result of case detection bias. In 338

the study in French Polynesia,1 because no specific imaging techniques were used, no special attention was paid to neurological disorders either at birth or during prenatal ultrasound screening. By contrast, the prospective study2 in Rio de Janeiro had a specific outcome—namely, the diagnosis of fetal neurological disorders related to seropositive gravidae. Furthermore, the pregnant women followed up had symptoms suggestive of Zika virus infection, whereas such a variable could not have been accounted for in the study in French Polynesia, since the proportion of infected gravidae was an estimation based on results from a population serosurvey. Therefore, it seems very likely that pregnant women presenting with a combination of rash plus positive RT-PCR results for Zika virus could have higher viraemia than those with seroconversion alone. The hypothesis that clinical complications are more common in individuals who have clinical symptoms of Zika virus infection is further supported by findings from another study in French Polynesia,3 in which 37 (88%) of 42 individuals diagnosed with Guillain-Barré syndrome also presented with viral syndrome (ie, rash, arthralgia, or fever) and almost all (98%) had laboratory confirmation of Zika virus infection. The proportion of symptomatic patients among those with viraemia is estimated at 20%.4,5 Clearly, further studies are needed to understand the risks of malformations associated with Zika virus infection, which are not restricted to microcephaly. We suggest that the presence of symptoms in patients with Zika virus infection could be an important surrogate marker of such developmental disorders and should be taken into consideration, especially when prognosticating pregnant women. We declare no competing interests. We acknowledge financial support from the Brazilian funding agency National Council for Scientific and Technological Development (CNPq). MHN and MRD were supported by research fellowship grants from CNPq.

*André Ricardo Ribas Freitas, Marcelo Henrique Napimoga, Maria Rita Donalisio [email protected] Laboratory of Immunology and Molecular Biology, São Leopoldo Mandic Institute and Research Center, Campinas, São Paulo 13015904, Brazil (ARRF, MHN); Laboratory of Spatial Analysis of Epidemiological Data, School of Medical Sciences, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil (MRD); and Campinas Department of Health, Division of Health Surveillance, Campinas, São Paulo, Brazil (ARRF) 1

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Cauchemez S, Besnard M, Bompard P, et al. Association between Zika virus and microcephaly in French Polynesia, 2013–15: a retrospective study. Lancet 2016; 387: 2125–32. Brasil P, Pereira JP Jr, Raja Gabaglia C, et al. Zika virus infection in pregnant women in Rio de Janeiro—preliminary report. N Engl J Med 2016; published online March 4. DOI:10.1056/ NEJMoa1602412. Cao-Lormeau VM, Blake A, Mons S, et al. Guillain-Barré syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study. Lancet 2016; 387: 1531. Duffy MR, Chen TH, Hancock WT, et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med 2009; 360: 2536–43. Petersen EE, Staples JE, Meaney-Delman D, et al. Interim guidelines for pregnant women during a Zika virus outbreak—United States, 2016. MMWR Morb Mortal Wkly Rep 2016; 65: 30–33.

Authors’ reply The Zika virus epidemic in the Americas has been quickly followed by multiple attempts to quantify the association between the infection in pregnant women and microcephaly. It has become difficult to gain a coherent picture from estimates that are often based on different measures, in different populations, and with different case definitions. Understanding the mechanisms that might explain apparent discrepancies is essential to strengthening the risk assessment of Zika virus. Therefore, the Correspondence by André Ricardo Ribas Freitas and colleagues is particularly timely. Why is the risk of microcephaly in pregnant women with symptomatic Zika virus infection in Rio de Janeiro1 found to be higher than our estimates for women with any type of Zika virus infection (with or without symptoms) in French Polynesia?2 www.thelancet.com Vol 388 July 23, 2016