Zika: Questions That Need Answers
Similar to the spread of the West Nile Virus to North America more than a decade ago, Zika originated in Africa but has recently spread through tropical regions around the world, causing illness in populations that have never encountered it before. In Brazil, the emergence of Zika was followed by an increase in cases of congenital microcephaly (abnormally small heads in newborns) as well as other neurological disorders. This moved the World Health Organization (WHO) to declare the Zika outbreak a Public Health Emergency of International Concern on February 1. By March 17, there were 30 cases of Zika reported in Canada, in people who contracted the disease while traveling outside the country. Unlike the West Nile Virus, which is transmitted by mosquitos in southern Canada, Zika virus transmission has so far remained in tropical and sub-tropical zones where other types of mosquitos are found.
The WHO is now coordinating an international response, including Canada, to help stop the outbreak. This coordination is essential to make diagnostic tests available, better understand and prevent congenital anomalies and other neurological disorders, speed up development of treatments and vaccines, share data, and scale up effective methods to combat mosquitoes.
To fight the disease, there is an urgent need to know more about the Zika virus infection, including rates of asymptomatic infection, implications for pregnancy, persistence of virus infection in bodily fluids, and the related risks of transmission. Researchers also seek to know whether there are other ways, besides mosquito bites, by which the virus is transmitted. How do we quickly and reliably diagnose Zika? What are the effects of the virus on human health in the immediate, medium, and long term? Can we confirm the causal link between the virus and the severe neurological complications reported, and explore other factors that could cause them? How and why do the effects vary? What are the ecological and epidemiological conditions that the virus needs to be transmitted? And how can we control, or better yet, prevent this virus from spreading? Canada has expertise and innovations to contribute to discovery and research efforts.
What we do know is that the Zika virus, like similar viruses such as Chikungunya and Dengue, is transmitted by the bite of an infected mosquito known as Aedes aegypti. Health officials are reporting that the virus is prevalent in dense urban areas, where mosquitoes have greater contact with people, breed in stagnant water, and thrive in weak infrastructure and poor sanitary conditions. We also know that, until there are preventive or therapeutic treatments in place to fight Zika, the most sustainable way to control transmission is to combat the vector – the mosquito. The bad news is that insecticides have their limitations. Mosquitoes can avoid them, become resistant, or quickly re-infest treated areas.
The good news is that we have other, more effective, and environmentally friendly options. In the last decade, IDRC has invested $7 million in the fight against Dengue in Latin America. Some of this research in partnership with the WHO’s Special Programme for Research and Training in Tropical Diseases, and led by Latin American experts, promotes an approach focusing on mobilizing community members to detect and eliminate mosquito breeding sites, usually standing water collecting in containers or in piles of waste such as old tires, cans, and construction debris. This approach reduces the mosquito population. Putting screens on doors and windows, applying insecticide to window curtains, and treating standing water that cannot be eliminated are additional strategies to prevent the Dengue, Zika, and other diseases transmitted by the same mosquitos. As a result, five sites hit by Dengue in Latin America have seen a considerable reduction in the number of mosquitoes, including up to 70% fewer in one study area in Colombia. In Fortaleza, Brazil, mosquito population increases during the rainy season were 16 times lower in areas that used the community-based environmental control approach than those areas that used standard insecticide spraying to control adult mosquitos.
In May 2015, Brazil’s national Dengue control program rolled out the community-based mosquito control approach in about 15,000 households in both Goias and Belo Horizonte as part of an initial scaling-up process to control Dengue, but that could also help curb Zika. Such research is demonstrating that it is possible to control the mosquitoes, but it requires considerable ongoing effort by community members and public health authorities in affected areas.
Other research is exploring how to control Dengue and Zika by modifying the mosquitoes so that they cannot breed or so that they cannot transmit viruses. Still others are searching for vaccines to prevent infectious diseases like Dengue and Zika. But until such break-through innovations are tested and proven effective, mosquito control remains the best defense.
Because of these past investments in vector control research in Latin America and our world-class expertise in vaccine and treatment research against infectious diseases, recently used to fight Ebola, Canada is ready and able to join the global fight against the new threat of Zika. There are still many questions about the Zika virus and its impact on human health. But it’s important to keep in mind that research has already provided us with many answers.
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