Zika outbreak: Babies exposed to virus developed microcephaly after birth, study finds

Thirteen babies in Brazil bornwith normal head circumference have been diagnosed withcongenital Zika syndrome, with brain scans showing extensivemalformations, inflammation and reduced brain volume,researchers reported on Tuesday.

Of the 13 infants, 11 gradually developed the birth defectmicrocephaly, or abnormally small head size, in the months
following birth.

• Zika emergency over, but still needs 'intense action:' WHO
• Zika infection found in newborns without microcephaly

The findings raise new concerns about the hidden effects ofpre-natal exposure to the mosquito-borne Zika virus, which hasbeen shown to cause birth defects when women become infectedduring pregnancy.

On Friday, the World Health Organization declared the globalZika emergency over because the link between Zika and
microcephaly has been confirmed. WHO intends to continuestudying Zika as a serious infectious disease that will requireyears of research.

Although others have observed neurological problems ininfants exposed to Zika during gestation, the study is the first
to carefully document birth defects in a group of babies withconfirmed Zika exposure whose head circumference fell into thenormal range at birth.

The study, published on Tuesday in the U.S. Centers forDisease Control and Prevention's weekly report on death and
disease, was done by teams in Recife and Fortaleza innortheastern Brazil.

Definition of syndrome expands

Eleven of the infants were born with heads that were on thesmall side and were referred for evaluation shortly after birth.The remaining two, born with normal head circumferences, werereferred for evaluation at 5 to 7 months because ofdevelopmental concerns.

Among the observed symptoms, 10 of the 13 babies had troubleswallowing, seven had epilepsy, five showed some degree ofirritability, nine could not voluntarily move their hands andall had hypertonia, or excessively stiff muscle tone.

In a conference call with reporters on Tuesday, WHOofficials said the fact that children can be born with normalhead size but later develop microcephaly demonstrates that thedefinition of congenital Zika virus syndrome the term WHO hasassociated with Zika-related birth defects continues toexpand.

The CDC now recommends monitoring babies born to Zika-infected women after birth, but the agency is looking at whether additional imaging should be recommended, said CDC Director Dr. Tom Frieden.

Investigators are working to determine what proportion of Zika-infected women have babies with birth defects, and how the risk varies based on when during the pregnancy the infection occurred. Earlier research has suggested that 1 per cent to 14 per cent of Brazilian mothers infected in the first three months of pregnancy had babies with microcephaly and that the risk falls when infections happens later in the pregnancy.

Dr. Anthony Costello, WHO's expert on maternal, newborn,child and adolescent health, said some 2,100 babies in Brazilhave had confirmed cases of microcephaly related to Zika. Heexpects another 1,000 cases to be confirmed as doctors continueto investigate a backlog of suspected cases.

"We know the problem has not gone away in Brazil," he said.