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 Zika transmission has not yet been reported in the continental
United States, although a woman who fell ill with the virus in
Brazil later gave birth to a brain-damaged baby in Hawaii.
Brazil's Health Ministry said in November that Zika was linked to a
fetal deformation known as microcephaly, in which infants are born
with smaller-than-usual brains.
Brazil has reported 3,893 suspected cases of microcephaly, the WHO
said last Friday, over 30 times more than in any year since 2010 and
equivalent to 1-2 percent of all newborns in the state of Pernambuco,
one of the worst-hit areas.
The Zika outbreak comes hard on the heels of the Ebola epidemic in
West Africa, demonstrating once again how little-understood diseases
can rapidly emerge as global threats.
"We've got no drugs and we've got no vaccines. It's a case of deja
vu because that's exactly what we were saying with Ebola," said
Trudie Lang, a professor of global health at the University of
Oxford. "It's really important to develop a vaccine as quickly as
possible."
Large drugmakers' investment in tropical disease vaccines with
uncertain commercial prospects has so far been patchy, prompting
health experts to call for a new system of incentives following the
Ebola experience.
"We need to have some kind of a plan that makes (companies) feel
there is a sustainable solution and not just a one-shot deal over
and over again," Francis Collins, director of the U.S. National
Institutes of Health, said last week.
The Sao Paulo-based Butantan Institute is currently leading the
research charge on Zika and said last week it planned to develop a
vaccine "in record time", although its director warned this was
still likely to take three to five years.
British drugmaker GlaxoSmithKline <GSK.L> said on Monday it was
studying the feasibility of using its vaccine technology on Zika,
while France's Sanofi <SASY.PA> said it was reviewing possibilities.
RIO CONCERNS
The virus was first found in a monkey in the Zika forest near Lake
Victoria, Uganda, in 1947, and has historically occurred in parts of
Africa, Southeast Asia and the Pacific Islands. But there is little
scientific data on it and it is unclear why it might be causing
microcephaly in Brazil.
Laura Rodrigues of the London School of Hygiene and Tropical
Medicine said it was possible the disease could be evolving.
If the epidemic was still going on in August, when Brazil is due to
host the Olympic Games in Rio de Janeiro, then pregnant women should
either stay away or be obsessive about covering up against mosquito
bites, she said.
The WHO advised pregnant women planning to travel to areas where
Zika is circulating to consult a healthcare provider before
traveling and on return.
The clinical symptoms of Zika are usually mild and often similar to
dengue, a fever which is transmitted by the same Aedes aegypti
mosquito, leading to fears that Zika will spread into all parts of
the world where dengue is commonplace.
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More than one-third of the world’s population lives in areas at risk
of dengue infection, in a band stretching through Africa, India,
Southeast Asia and Latin America.
Zika's rapid spread, to 21 countries and territories in the Americas
since May 2015, is due to the prevalence of Aedes aegypti and a lack
of immunity among the population, the WHO said in a statement.
RISK TO GIRLS
Like rubella, which also causes mild symptoms but can lead to birth
defects, health experts believe a vaccine is needed to protect girls
before they reach child-bearing age.
Evidence about other transmission routes, apart from mosquito bites,
is limited.
"Zika has been isolated in human semen, and one case of possible
person-to-person sexual transmission has been described. However,
more evidence is needed to confirm whether sexual contact is a means
of Zika transmission," the WHO said.
While a causal link between Zika and microcephaly has not yet been
definitively proven, WHO Director-General Margaret Chan said the
circumstantial evidence was "suggestive and extremely worrisome".
In addition to finding a vaccine and potential drugs to fight Zika,
some scientists are also planning to take the fight to the
mosquitoes that carry the disease.
Oxitec, the UK subsidiary of U.S. synthetic biology company Intrexon
<XON.N>, hopes to deploy a self-limiting genetically modified strain
of insects to compete with normal Aedes aegypti.
Oxitec says its proprietary OX513A mosquito succeeded in reducing
wild larvae of the Aedes mosquito by 82 percent in an area of Brazil
where 25 million of the transgenic insects were released between
April and November. Authorities reported a big drop in dengue cases
in the area.
(Editing by Mark Trevelyan)
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