A DNA analysis of the mosquito-borne virus, which has infected
almost 300 people in Singapore, including two pregnant women,
revealed slight differences between the strains but it was not clear
what that meant in terms of the severity of the disease, the health
The World Health Organization (WHO), which has declared Zika an
international health emergency, says more research is needed to
determine the effects of the different Zika strains.
"There is no evidence from existing studies and from this sequence
to indicate whether the differences between these strains and the
South American virus correlate with differences in severity or type
of disease," the health ministry said.
"Correlation of virus strains with specific clinical manifestations
will take long-term careful epidemiological studies as well as
experimental studies," it added.
The WHO has said that infection with the virus in pregnant women can
cause the birth defect microcephaly, in which the brain and head of
the baby are undersized, and other severe brain abnormalities.
The WHO also said it was likely that the Zika virus could trigger
the Guillain-Barre syndrome, a rare neurological disorder that can
result in paralysis, though conclusive proof may take years.
The connection between the virus and microcephaly first came to
light in Brazil, which has been the hardest hit by the outbreak
affecting Latin America.
Scientists say the Zika strain in Brazil most likely evolved from an
Asian strain. The virus, first detected in Uganda in 1947, spread to
equatorial Asia in the 1960s and 1980s.
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Singapore said the strain causing the current outbreak also evolved
from an Asian strain. Raymond Lin, head of the National Public
Health Laboratory said the strain in Singapore and Brazil were
slightly different, but it was not clear what this meant.
"There might be fine differences, there might be more mutations but
currently there is no evidence at all to suggest that it's less
severe or more severe; whether there is less or more likelihood of
getting microcephaly," he told media.
A WHO spokeswoman also said more research was needed to better
understand the virus.
"Researchers do not yet know if the 'old' lineage of Zika also
causes complications such as microcephaly and neurological
disorders," the spokeswoman said.
(Editing Miral Fahmy, Robert Birsel)
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