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WHO Director-General briefs the media on the Zika situation

WHO statement
22 March 2016

Ladies and gentlemen,

I welcome this opportunity to update you on developments in science and the Zika evidence base that have built up since 1 February.

The world was alerted to the first appearance of Zika in the Western Hemisphere on 7 May 2015, when Brazil confirmed that a mysterious outbreak of thousands of cases of mild disease with rash was caused by the Zika virus.

The appearance of an infectious disease with epidemic potential in a new part of the world is always cause for concern.

The absence of population immunity gives the virus license to spread rapidly and behave in possibly unexpected ways.

At the time of the May announcement, the disease looked reassuringly mild, with no hospitalizations or deaths reported. Past experience has taught us to expect more from emerging viruses than what is initially observed.

This came from Brazil in July with a reported increase in cases of Guillain-Barré syndrome, followed by an unusual increase in microcephaly among newborns, reported to WHO in late October.

The possibility that a mosquito bite could be linked to severe fetal malformations alarmed the public and astonished scientists.

The association with Guillain-Barré syndrome and other severe disorders of the central nervous system has expanded the risk group well beyond women of child-bearing age.

We now know that sexual transmission of the virus occurs.

In less than a year, the status of Zika has changed from a mild medical curiosity to a disease with severe public health implications.

The knowledge base is building very rapidly. I want to thank all countries and their scientists who have worked so hard in helping WHO build up the evidence base.

The more we know the worse things look.

A pattern has emerged in which initial detection of virus circulation is followed, within about three weeks, by an unusual increase in cases of Guillain-Barré syndrome.

Detection of microcephaly and other fetal malformations comes later, as pregnancies of infected women come to term.

In the current outbreak, Brazil and Panama have reported microcephaly. Colombia is investigating several cases of microcephaly for a possible link to Zika. In other countries and territories, the virus has not been circulating long enough for pregnancies to come to term. A WHO team is currently in Cabo Verde to investigate the country’s first reported case of microcephaly.

To date, 12 countries and territories have now reported an increased incidence of Guillain-Barré syndrome or laboratory confirmation of Zika infection among GBS cases.

Additional effects on the central nervous system have been documented, notably inflammation of the spinal cord and inflammation of the brain and its membranes.

The virus is currently circulating in 38 countries and territories. On present knowledge, no one can predict whether the virus will spread to other parts of the world and cause a similar pattern of fetal malformations and neurological disorders.

If this pattern is confirmed beyond Latin America and the Caribbean, the world will face a severe public health crisis.

Ladies and gentlemen,

We need to build the knowledge base quickly, very quickly.

Since 1 February, WHO has convened seven international meetings and published 15 documents that translate the latest research into interim practical guidance to support countries as they respond to this outbreak and its neurological complicatoins.

Over the past two weeks, WHO convened three high-level meetings to look at the science, the convention and new tools for mosquito control, and what we know about the management of complications, including microcephaly and Guillain-Barré syndrome. These meetings help answer pressing scientific questions and gather advice on the best ways to respond to a situation that is rapidly evolving.

The science meeting looked at the evidence linking Zika infection with fetal malformations and neurological disorders. Though the association is not yet scientifically proven, the meeting concluded that there is now scientific consensus that Zika virus is implicated in these neurological disorders. The kind of urgent action called for by this public health emergency should not wait for definitive proof.

In terms of new medical products, the experts agreed that a reliable, point-of-care diagnostic test is the most urgent priority. At present, more than 30 companies are working on, or have developed, potential new diagnostic tests.

For vaccines, 23 projects are being worked on by 14 vaccine developers in the US, France, Brazil, India, and Austria. As the vaccine will be used to protect pregnant women or women of child-bearing age, it must meet an extremely high standard of safety.

WHO estimates that at least some of the projects will move into clinical trials before the end of this year, but several years may be needed before a fully tested and licensed vaccine is ready for use.

Several scientists warned that the first explosive wave of spread may be over before a vaccine is available. However, all agreed that development of a vaccine is imperative. More than half of the world’s population lives in an area where the Aedes aegypti mosquito is present.

During the meeting on mosquito control, the experts concluded that well-implemented control programmes using existing tools and strategies are effective in reducing the transmission of Aedes-borne diseases, including Zika. However, they also identified a number or challenges in implementing these tools.

The experts evaluated the potential impact of five new tools for mosquito control. None was judged ready for full-scale implementation.

While investigations of all five should continue, the experts recommended carefully planned pilot deployment of two: namely, microbial control, using Wolbachia bacteria, of human pathogens in adult mosquitoes, and the use of genetic manipulation to reduce mosquito populations.

The third meeting looked at the management of complications, including fetal malformations and neurological disorders, and the heavy burden this places on health systems. Evidence supports the likelihood that Zika infection during pregnancy will have a broad range of effects on the developing fetus, beyond microcephaly.

As the experts concluded, a shift in thinking is needed, away from the management of individual cases and towards the longer-term building of capacities to cope with these added burdens.

Fetal malformations place a heart-breaking strain on families and communities as well as systems for health care and social support. Neurological disorders like Guillain-Barré syndrome call for added capacity to provide life-saving intensive care.

Thank you.