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WHO declares Zika virus a public health emergency

3 February 2016

The World Health Organization has declared the recent outbreak of the Zika virus in Latin American countries a public health emergency. The mosquito-borne disease, which carries symptoms such as mild fever and joint pains, has recently been linked to increased cases of microcephaly – a condition that leads to a variety of neurological and developmental disorders in newborn babies. There is no treatment or vaccine currently available.

In the absence of treatment, the best way to reduce the number of Zika virus cases is preventing mosquito bites. The mosquito species responsible for spreading the virus, Aedes aegypti, also carries dengue, yellow fever and chikungunya, so reducing their numbers will have knock-on benefits for other diseases. Unlike the Anopheles mosquito which transmits malaria, Aedes aegypti is active during the day, limiting the protection provided by mosquito nets. With political will and high investment from donors and governments, however, the mosquito populations can be reduced through other means.

Aedes mosquitoes lay their eggs mainly in water containers often quite close to houses.  So the main vector control measures are to empty or remove containers or treat the water with insecticides with low toxicity to humans.  In some environments outdoor fogging has been attempted during major outbreaks of dengue, and there is mixed evidence on its effectiveness.  Availability of information is also crucial. Some governments, such as Brazil’s, are already pursuing public health campaigns to inform people how they can protect themselves from bites – for example, by disposing of standing water where mosquitoes breed.  Communities can do a great deal to make their neighbourhoods safer given sound advice and effective mobilisation.

It is important to look into new and innovative methods of vector control, too. Malaria Consortium has been exploring ways to reduce the Aedes aegypti population in Asia in an attempt to reduce cases of dengue. One study focuses on the feasibility of introducing predators like guppy fish in standing water where mosquitos breed. Another one explores the use of insecticide-treated clothing to kill mosquitoes and disrupt transmission of malaria, but could prove useful also to control Aedes.

While these are not likely to be end-all solutions, they add to a growing arsenal of tools to fight mosquito-borne diseases. More commitment and funding for research as well as scaling up proven vector control methods will ensure that outbreaks of this kind can be rapidly stopped.   

We hope, at least, that the global attention now focused on Aedes mosquitoes can draw more attention to the hugely neglected control of the other diseases it transmits, particularly dengue, a potentially fatal disease infecting several million people each year. 

Keywords: Vector control | Advocacy and policy

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