WHO Needs Much More Evidence and Time to Link Zika Virus With Microcephaly

Though there are several reports of evidence linking Zika virus to microcephaly, the World Health Organization has said that it could still take months to determine for certain that the Zika virus causes the serious birth defect. "There is an increasing accumulation of evidence now that these phenomena may be associated," said Bruce Aylward, WHO chief on outbreaks and health emergencies.

The mosquito-borne Zika virus, which has been spreading explosively in Latin America especially, is strongly suspected of causing a rapid rise in the number of children born with microcephaly -- abnormally small heads and brains -- in the hardest-hit country, Brazil.

A hike in microcephaly cases was also registered following a Zika outbreak in French Polynesia three years ago.

The virus is also believed to be tied to a rise in cases of the paralysis-causing Guillain-Barre syndrome in eight countries, including Brazil, Colombia, El Salvador and Venezuela.

Aylward said researchers would likely be able to prove more quickly that Zika causes Guillain-Barre than microcephaly, since surges in the syndrome are believed to be lagging only about three weeks after spikes in Zika infections.

By comparison, it will take much longer to register a spike in microcephaly in babies born to women infected with Zika at some point during their pregnancies, he said.

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Meanwhile, "the virus is considered guilty until proven innocent," Aylward said, stressing "the need to be super aggressive" in trying to rein in the Aedes aegypti mosquito, which carries Zika and also dengue and chikungunya viruses.

The mosquito is endemic to tropical regions, and is already transmitting Zika in at least 36 countries worldwide -- 28 of them in the Americas -- and Aylward said there were indications that the virus was spreading in six additional countries.

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"We are still dealing with a very much evolving situation," Aylward cautioned.

There is currently no cure or vaccine for Zika, so in a bid to beat it, affected countries have declared war on the Aedes aegypti, trying to wipe out breeding spots, kill larvae either with chemicals or with fish that feed on them, and fumigation to kill off adult mosquitoes.

Pedro Alonso, head of WHO's global malaria program, told reporters the agency would in mid-March convene a meeting of the world's top experts on vector control to determine if a range of radical new methods could also be safely and efficiently used.

They include releasing genetically modified mosquitoes, or releasing large numbers of sterilized male mosquitoes to halt reproduction.

Another method being studied is infecting mosquitoes with a bacteria, the Wolbachia, that does not infect humans and that can prevent mosquito eggs from hatching and can reduce a mosquito's ability to transmit a virus.

The meeting, Alonso said, will "assess whether there is room for fast-tracking one or several of these new strategies. He stressed though that in the meantime, the more traditional methods "can have a very major impact. We are not waiting for a magic bullet," he said.

Source-AFP