Zika virus link to microcephaly could take 6 months to prove: WHO

The World Health Organization says it could take four to six months to say with certaintywhether the Zika virus is associated with the birth defect microcephaly.

At a news conference in Geneva on Friday, Dr.Bruce Aylward,WHO'sexecutivedirector of outbreaks and health emergencies, saidcausation has not been proved,but they continue to proceed as if the association is causal or "guilty until proven innocent" for both microcephaly andGuillain-Barrsyndrome, arare disorder of muscle weakness and sometimes paralysis.

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Aylward said they are getting more informationshowing a stronger associationbetweenmicrocephaly, characterized byan abnormally small headandincomplete brain development at times,and infection with the virus. The balance will probably tip once women in Colombia and other countries give birth, meaning mid-summer at the latest.

"A lot can be done in terms of reducing the intensity of Zika transmission and the accumulating evidence is that this has got to be done and done very, veryurgently,because there is a very real possibility that this virus could be responsible for some of the horrific consequences we've been talking about in terms of children affected by this disease," he said.

Link probed

The investigation testing the link between Zika virus and microcephalywas sparked afterBrazilian doctors noticed an increase last fall in babies with thebirth defect. There are many causes, both infectious and non-infectious.The cases closely followed the country's first outbreak of the tropical virus Zika.

WHO has declared the clusters of microcephaly and other neurological complications associated with Zika"an extraordinary event and public health threat to other parts of the world."

Preliminary results of the two case control studiesconducted by the U.S. Centers for Disease Control and Prevention
and Brazilian biomedical research centres in the northeasternstates of Bahia and Paraiba should be ready "this spring," saidCDC principal deputy director Anne Schuchat.

"Scientists are increasingly confident that Zika is causingmicrocephaly, but people may have different judgments about howmuch proof is enough," Schuchat told reporters during a two-daymeeting in the Brazilian capital.

In the case-control studies, "cases" or babies born with microcephalyare compared in detail with those born without the condition. Researchers are checking for risk factors such as whether the mothershad symptoms of the Zika virus during their pregnancies, and if so, inwhich trimester, as well as looking at otherpotential exposures during pregnancy, such as other infections or environmental toxins.

'Tenacious menace'

The virus itselfcauses a mild illness for about a week, and on its ownwouldn't have triggered an emergency.

To reduce transmission, efforts focus on controlling the Aedesaegypti mosquito thatthe UNhealth body has described as an "opportunistic and tenacious menace."

Dr. Pedro Alonso, director of WHO's global malaria program, described proven and experimentalmosquito control strategies, such as fogging to getrid of adults,useof fish with an appetite for larvae, and ways to eliminate the larvae.

"It is not that we're waiting for a magic bullet of one of these new, fancy, potentially important new technologies,but a lot can be done in terms of controlling this outbreak and massively reducing the disease burden with currently available tools and strategies," Alonsosaid.

As of today, 36 countries are known to have transmission of the virus, including 28 in theAmericas,Aylwardsaid.