Background-From October 2013 to April 2014, French Polynesia experienced the largest Zika virus (ZIKV) outbreak ever described at that time. During the same period, an increase in GuillainBarré syndrome (GBS) was reported, suggesting a possible association between ZIKV and GBS.

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With the introduction of more efficient treatments for hepatitis C virus (HCV), improved epidemiological information is required at the country level to allow evidence-based policymaking for elaboration of national strategies and HCV resources planning. We present a systematic review with meta-analysis of HCV seroprevalence data in adults in African countries. We conducted a systematic review of all HCV seroprevalence estimates reported in African countries from 2000 to 2014 in MEDLINE, AJOL and grey literature. We assessed studies performed in the general population and among blood donors, pregnant women and HIV-positive patients. A meta-regression analysis was used to provide adjusted estimates of HCV seroprevalence in the general adult population in each country, accounting for the heterogeneity in sample age structure and population types in the included studies. We identified 775 national-level estimations, among which 184 were included. Estimates of HCV seroprevalence were produced for 38 countries, in addition to the results from nationwide representative surveys available in Egypt and Libya. Next to Egypt, which clearly stands out, the highest levels of seroprevalence were found in Middle Africa (e.g. Cameroon, Gabon and Angola) and some West African countries (e.g. Burkina Faso, Benin), and the largest absolute numbers of infected adults were found in Nigeria, Ethiopia and Democratic Republic of Congo. This study exposes the diversity of HCV epidemiology among African countries. Egypt and several countries of West and Middle Africa present a HCV burden that will require strong governmental commitment to promote efficient preventive and curative interventions.

To the Editor: Killed oral cholera vaccines (OCVs) are part of the standard response package to a cholera outbreak, although the two-dose regimen of vaccines that has been prequalified by the World Health Organization (WHO) poses challenges to timely and efficient reactive vaccination campaigns. 1 Recent data suggest that the first dose alone provides short-term protection, similar to that of two doses, which may largely dictate the effect of OCVs during epidemics. [2][3][4] A cholera outbreak was detected in Lusaka, Zambia, in February 2016, after a period of 4 years without a reported case of cholera. An emergency reactive vaccination campaign was implemented in April 2016, targeting more than 500,000 persons who were at high risk for cholera in Lusaka (population, >2 million persons). The Ministry of Health, with support from Médecins sans Frontières and the WHO, decided to implement a single-dose campaign to quell the epidemic rapidly, in view of the insufficient number of vaccine doses that were available in the global stockpile to complete a two-dose campaign. In December 2016, when more doses became available, a second round of vaccination was organized and the second vaccine dose was offered to persons at risk.We conducted a matched case-control study to quantify the short-term effectiveness of a single-dose OCV regimen (Shanchol) between April 25, 2016, and June 15, 2016. The study was approved by two institutional review boards, and written informed consent was obtained from all the participants (see the Supplementary Appendix, available with the full text of this letter at NEJM.org). Cases of cholera were confirmed by means of culture, polymerase-chain-reaction as-

Two community-based density case-control studies were performed to assess risk factors for cholera transmission during inter-peak periods of the ongoing epidemic in two Haitian urban settings, Gonaives and Carrefour. The strongest associations were: close contact with cholera patients (sharing latrines, visiting cholera patients, helping someone with diarrhoea), eating food from street vendors and washing dishes with untreated water. Protective factors were: drinking chlorinated water, receiving prevention messages via television, church or training sessions, and high household socioeconomic level. These findings suggest that, in addition to contaminated water, factors related to direct and indirect inter-human contact play an important role in cholera transmission during inter-peak periods. In order to reduce cholera transmission in Haiti intensive preventive measures such as hygiene promotion and awareness campaigns should be implemented during inter-peak lulls, when prevention activities are typically scaled back.