Four updates on scientific aspects of Zika

Zika virus epidemic: Africa should not be neglectedby Nicolas Meda, Sara Salinas, Thérèse Kagoné, Yannick Simonin, Philippe Van de PerreLancet Correspondence 388(10042):337–338. 23–29 July 2016The Zika virus was first isolated in Uganda in 1947. Despite the recent severe outbreak of Zika virus in Cape Verde, with 7,557 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…Aedes aegypti [mosquitoes], the main vector of Zika virus… are mainly present in sub-Saharan Africa… 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 3,000 consecutive births in Lagos, Nigeria, in 2012…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.…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…*****************************************The first case of female-to-male sexual transmission of the Zika virus reported Centers for Disease Control and Prevention Morbidity & Mortality Weekly Report, 22 July 2016The first case of female-to-male sexual transmission of the Zika virus has been documented in New York City.Current guidance to prevent sexual transmission of Zika virus has been based on the assumption that transmission occurs from a male partner to a receptive partner. Ongoing surveillance is needed to determine the risk for transmission of Zika virus infection from a female to her sexual partners.Persons who want to reduce the risk for sexual transmission of Zika virus should abstain from sex or correctly and consistently use condoms for vaginal, anal, and oral sex, as recommended in the current CDC guidance (5). Guidance on prevention of sexual transmission of Zika virus, including other methods of barrier protection, will be updated as additional information becomes available.*****************************************Promising new tools to fight Aedes mosquitoes Organization, by Andréia Azevedo Soares 2016;94:562–563DOI: new tools for suppressing Aedes aegypti mosquito populations have been recommended for pilot testing. Trials are needed to see whether they actually reduce disease as well.Scientists released 12 000 to 15 000 Wolbachia-infected mosquitoes every week for 20 weeks in this suburb of Rio de Janeiro from September 2014 and repeated this a year later. Wolbachia is a bacterium that stops den­gue, chikungunya and Zika viruses from replicating inside their mosquito vectors. When Wolbachia-infected mosqui­toes mate with wild mosquitoes, they pass Wolbachia on to the next generation. If all goes to plan, most mosquitoes in Tubia­canga and Jurujuba, another neighbour­hood involved in the study, will carry Wolbachia and be unable to transmit the three viruses to humans.After almost a decade of research, O’Neill’s team managed to rear mosqui­toes carrying Wolbachia in the laboratory. The first Wolbachia-infected Aedes were released in 2011 in Cairns, a small coastal city in Queensland, Australia. O’Neill’s team did a similar experiment in Townsville, 346 km to the south, in Octo­ber 2014 and other members of the research consortium have done similar field trials in Colombia, Indonesia and Viet Nam. Wolbachia-infected Aedes aegypti was one of five promising new tools to reduce mosquito populations discussed at an emergency meeting of the World Health Organization (WHO) Vector Control Advisory Group in March in Geneva. The meeting was held a month after WHO declared the Zika epidemic an international public health emergency. At that meeting, experts from the Vector Control Advisory Group reviewed four other new tools: transgenic mos­quitoes called Oxitec OX513A, vector traps, the sterile insect technique and the attractive toxic sugar bait. They recommended the pilot de­ployment of two contrasting approaches: Wolbachia-infected Aedes aegypti mos­quitoes and Oxitec transgenic mosqui­toes to see whether the latter reduces mosquito populations when released on a large scale.While the Wolbachia approach aims to make Aedes mosquito populations less harmful to human health, the Oxitec ap­proach seeks to reduce the size of these populations… According to Oxitec, the company that developed the transgenic mosquitoes, five small-scale trials in Brazil, the Cayman Islands and Panama led to a reduction of more than 90% in mosquito populations. Oxitec is awaiting approval from the United States Food and Drug Adminis­tration to do a large-scale trial near Key West in the southern state of Florida… Luciano Moreira, proj­ect leader at the Oswaldo Cruz Foundation said: “Now we’re ready to scale-up the project. If we begin today, in three years we would have the capacity to cover a city like Rio de Janeiro.” ……“The large-scale use of insecticide-treated bednets (ITNs) and indoor residual spraying have contributed significantly to the decline of malaria, for example,” says Dr Abraham Mnzava, coordinator of entomology and vector control in the Global Malaria Programme department. However, ITNs are of limited use against Aedes because these mosquitoes bite during the day. Traditional ap­proaches to tackling Aedes mosquitoes, such as fogging and space-spraying with insecticides and larvicides in household water storage containers, have been deployed for decades while dengue epi­demics and resistance to insecticides have continued to grow.*****************************************Could clinical symptoms be a predictor of complications in Zika virus infection?This letter is in response to an article that reviews the literature on whether clinical symptoms of Zika could be a predictor of complications from Zika infection. The authors say they think it seems 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. But they say that further studies are needed to understand the risks of malformations associated with Zika virus infection, which are not restricted to microcephaly. REPLY:Lancet 388(10042):338, 23–29 July 2016, by André Ricardo Ribas Freitas, Marcelo Henrique Napimoga, Maria Rita DonalisioAuthors’ reply (summary): 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…Overall, we agree with Freitas and colleagues that comparison of the two studies supports the hypothesis that the risk of microcephaly might increase with the presence of symptoms in the infected mother. Since most infections are thought to be asymptomatic, a substantial proportion of Zika virus-related microcephaly could still come from women who did not have any symptoms. Follow-up of pregnant women with and without symptoms will be essential to better characterise this relation.Lancet 388(10042):338-339, 23–29 July 2016, by Simon Cauchemez et al.