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WHO warns of spray limitations for Zika virus

March 9, 2016

The UN's health agency has warned of the limitations of spraying against dengue fever. The WHO suggested the Zika virus may be similarly resistant.

Brasilien Bekämpfung Stechmücken Zika Virus
Image: Reuters/A. Machado

The World Health Organization (WHO) has said that widespread spraying to eliminate mosquitoes has failed to significantly stop the spread of dengue fever. The agency suggested it may be the same case for the Zika virus, which has been linked to neurological disorders, including microcephaly.

WHO Marie-Paule Kieny PK zu Zika Virus in Genf
WHO Assistant Director General Marie-Paule KienyImage: Reuters/P. Albouy

The announcement in Geneva on Wednesday came as Brazil's health ministry said the number of confirmed and suspected cases of microcephaly had risen to 4,976 - up from 4,863 a week earlier. Of these, the number of confirmed cases increased by a hundred in one week - to 745.

A three-day meeting of experts called for a quicker development of tools to diagnose Zika infections and of vaccines to prevent the disease.

WHO Assistant Director General Marie-Paule Kieny said experts concurred there was no evidence that traditional mosquito control methods had had any significant impact on transmission of dengue, a virus close to Zika.

"This is important because we must be sure that we invest in interventions that work," Kieny told a news briefing in Geneva on Wednesday. Instead, emphasis should be put on enlisting families and communities to protect themselves and eliminate mosquitoes from their homes.

Brasilien Zika Virus - Mikrozephalie - Mutter mit Baby
A mother with her baby who was born with microcephalyImage: picture-alliance/dpa/A. Lacerda

She said the Aedes aegypti species of mosquito that carries Zika is the "cockroach of mosquitoes" because it stays mainly indoors and is hard to eradicate.

Vaccines months away

Kieny said that the most advanced candidate vaccines for Zika were still a few months away from starting human clinical trials.

"It is, therefore, possible that vaccines may come late for the current Latin American outbreak, but the development of a vaccine remains an imperative, in particular vaccines suitable for pregnant women and women of child-bearing age," Kieny said.

Director of Brazil's Butantan Institute in Sao Paolo, Jorge Kalil, attended the meeting. He commented: "The problem right now is it's very difficult to fight the [mosquito]; there are billions and billions of insects."

Zika Virus
A scientist researching a possible Zika-repellent clothes detergent additiveImage: Reuters/I. Alvarado

Kieny said there had been a discussion on innovative methods such as using genetically modified mosquitoes to stop the outbreak. She noted that "extreme rigor" must be used in evaluating such new tools.

To date, there have been outbreaks of the Zika virus in 41 countries. Confirmed cases linking Zika to babies with birth defects have been recorded in Brazil and French Polynesia. Nine countries have reported an increase in the number of cases of Guillain-Barre syndrome, a neurological condition that typically affects people after infections.

jm/jil (Reuters, AP)