Zika virus likely to spread throughout the Americas, says WHO.
as only Canada and Chile expected to be free of
mosquito-borne disease
Zika virus: what you need to knowTwo of the world's biggest drug companies are
evaluating whether existing vaccine technology could
be used against the Zika virus, as the World Health
Organisation warned the mosquito-borne virus was
likely to spread to all countries in the Americas
except for Canada and Chile.
The WHO director general, Margaret Chan, told the
organisation's executive board that she had asked
Carissa Etienne, head of the WHO in the Americas, to
brief the board later this week on its response to the
outbreak. The mosquito-borne Zika virus has been
linked to brain deformities in babies.
Zika virus: its effects, how it is spread, and the
possible threat to women
"Although a causal link between Zika infection in
pregnancy and microcephaly has not – and I must
emphasise – has not been established, the
circumstantial evidence is suggestive and extremely
worrisome," Chan said. "An increased occurrence of
neurological symptoms, noted in some countries
coincident with arrival of the virus, adds to the
concern."
Zika is transmitted by the Aedes aegypti mosquito,
which is also known to carry the dengue, yellow fever
and Chikungunya viruses.
There is no vaccine or treatment for Zika, which
typically causes mild fevers and rashes, although
about 80% of those infected show no symptoms.
"We're concluding our feasibility studies as quickly as
we can to see if our vaccine technology platforms
might be suitable for working on Zika," Glaxo
spokeswoman Anna Padula told Reuters in an email.
France's Sanofi SA, which won approval late last year
for the first dengue vaccine, has also said it is
reviewing the possibility of applying its technology
for Zika. "However, there are too many unknowns
about Zika to reliably judge the ability to research
and develop a vaccine effectively," a spokesman said
last month.
The first outbreak of the disease outside of Africa,
Asia and the Pacific islands occurred in May 2015,
when a case was reported in Brazil.
It was previously considered to have relatively mild
consequences for those infected. But in November
Brazil's health ministry said that the virus was linked
to a foetal deformation known as microcephaly, in
which babies are born with smaller than normal
brains.
Brazil has reported almost 4,000 suspected cases of
microcephaly, the WHO said last Friday, over 30
times more than had been reported in any year since
2010.
Zika virus: health experts fear Carnival celebrations
will lead to spread
The WHO's warning came as the Brazilian authorities
announced plans to prevent the spread of the
disease during this summer's Olympic Games in Rio
de Janeiro, when about 500,000 tourists are expected
to descend on the city.
The WHO said the 21 countries predicted to be
affected are all those in the region that have Aedes
mosquitoes, which carry the virus. Zika has not yet
been reported in the continental United States,
though a woman who fell ill with the virus in Brazil
later gave birth to a baby with brain damage in
Hawaii.
The WHO attributed the rapid spread of Zika to the
fact that the population of the Americas had not
previously been exposed to it and so lacks immunity.
It said in a statement: "The role of Aedes mosquitoes
in transmitting Zika is documented and well
understood, while evidence about other transmission
routes 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."
It said there was no evidence of Zika being
transmitted to babies through breast milk. Pregnant
women planning to travel to areas where the virus is
circulating are advised to consult a healthcare
provider before travelling and on their return.
The Brazilian authorities said inspections of Olympic
facilities would begin four months before the Games
to get rid of mosquito breeding grounds and daily
sweeps would take place during the competition.
They added that fumigation would be an option but
would be limited because of concerns for the health
of the athletes and visitors.
Laura Rodrigues, professor of infectious disease
epidemiology at the London School of Hygiene &
Tropical Medicine, said evidence of a link with
microcephaly was strong. "Evidence includes
temporal association between Zika outbreaks and
microcephaly outbreaks both in Brazil and French
Polynesia," she said. "The virus is neurotropic. It
grows in the brain of the foetus and destroys brain
structures so the developing brain is malformed –
small – that's the cause of the microcephaly."
She said that there had previously been little
research on Zika as it was seen as of "no public
health importance", but the suggestion that it could
cause congenital infections and microcephaly had
changed that view.
Rodrigues suggested that with a major international
effort there could possibly be a vaccine within the
next couple of years.
Trudie Lang, professor of global health research at
Oxford University, said it was important that the
response from the research community was faster
than with Ebola.
"This is an important emerging disease outbreak
situation and we really must apply the lessons that
we learnt from Ebola because Zika could be a major
public health issue in these countries," she said.
"There are many unknowns and so research is
urgently needed to understand what is happening
and how to prevent further cases.
"There is no treatment and no vaccine and so this
would need addressing through clinical trials as
quickly as possible."
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