Zika: Then, now, and tomorrow
Where do we stand one year after WHO announced Zika as a public health emergency? International spread has continued, while surveillance has improved. In line with WHO advice, innovative approaches to mosquito control are being piloted in countries and WHO will provide sustained guidance for effective interventions and support for families, communities, and countries experiencing Zika virus.
They are tiny animals that live near or inside human dwellings where contact with people is high. Every few days, they lay 100-150 eggs which develop into adults in about a week. They are mosquitoes. The adult females feed on people’s blood, several times during the day. In the 1960s, thanks to the use of insecticides, Aedes mosquitoes were virtually eliminated from the Americas. Today, more than half of the world’s people live in areas where the Aedes mosquito lives, breeds, proliferates, feeds and infects people with viruses such as Zika virus, chikungunya, dengue and yellow fever. In late 2015, with no vaccine or treatment against Zika virus, mosquito control became the only line of defence when Brazil and other countries observed an upsurge of Zika virus infections and neurological complications.
“More than half of the world’s people live in areas where the Aedes mosquito lives, infecting people with viruses such as Zika virus, chikungunya, dengue and yellow fever.”
Dr Raman Velayudhan, Coordinator, vector ecology and management
I was amazed to see how fast authorities across the Americas, but also in Asia where Zika virus outbreaks had occurred in the past, have taken action to control transmission of Zika virus. Sometimes, even the army was involved! In Barranquilla, Colombia, Los Caminantes de la Salud – Hikers for Health – helped families inspect their backyards to remove, clean or turn upside down unused containers. When filled with rainwater, these are perfect sites for the mosquitoes to lay their eggs. Miami-Dade County in the United States sprayed insecticides from planes and thus managed to contain the outbreak in a small geographic area. In Tonga, the Ministry of Health and its partners sprayed in and around houses and handed out mosquito nets to pregnant women. In Singapore, the National Environmental Agency detected and destroyed about 130 mosquito breeding habitats to stop the cycle of transmission between mosquitoes and people.
Mosquito control can work. It has to be done, though, in a systematic and comprehensive way and sustained over time. In late 2016, we convened Member States, UN agencies, scientific and research groups and nongovernmental organizations to develop a longer-term strategy for the simultaneous control of many species, including Aedes mosquitoes that carry disease-causing organisms.
Besides research into how to counter growing insecticide resistance and scaling up existing control techniques, the draft global vector control response also includes improving water supply and solid waste management in expanding towns and cities. In addition, several countries have started to pilot novel techniques that WHO reviewed and recommended in 2016. Yes, they are tiny and often a step ahead of humans because they can adapt extremely well to new living conditions, but history has shown that control is feasible.