Zika outbreak: hearing loss found in 6% of Brazilian babies in study

Tests on small group of infants with microcephaly and evidence of Zika virus infection before birth suggests more than five per cent experienced hearing loss, researchers find.

Other viral infections during pregnancy can also cause hearing loss

 A study in Brazil of 70 babies whose mothers had confirmed Zika infections found that nearly 6 per cent had hearing loss, adding a new complication to the list of ills the virus can cause when women are infected during pregnancy.

The Brazilian study, published on Tuesday in the U.S. Centers for Disease Control and Prevention's weekly report on 
death and disease
, confirmed less rigorous reports of deafness among infants born to mothers with Zika infections.

The finding is part of an effort to fully characterize the harm caused by the Zika virus during pregnancy. The virus is best known for causing the severe birth defect microcephaly, characterized by undersized heads and underdeveloped brains. But other studies have shown that Zika can cause other brain abnormalities, vision problems and joint deformities.

In the latest study, a team at the Oswaldo Cruz Foundation in Pernambuco, Brazil, examined records from 70 infants with microcephaly whose mothers had laboratory-confirmed Zika infections during pregnancy.

They found that nearly 6 per cent had hearing loss without any other plausible cause.

Several other viral infections during pregnancy can cause hearing loss, including rubella and cytomegalovirus, or CMV,
infections. The current study adds Zika infection to that list.

WHO emergency committee for Zika meets Thursday

Scientists say Zika should now be considered a risk factor for hearing loss, and children who were exposed during pregnancy but have normal hearing at birth should be screened regularly for delayed or progressive hearing loss.

Meanwhile, the World Health Organization (WHO) said on Tuesday that its Emergency Committee on Zika would meet on Thursday to review the outbreak's evolution and neurological birth defects linked to the mosquito-borne virus.

The panel of independent experts led by Dr. David Heymann, which last met on June 14, convenes every three months to assess progress in the fight against the disease and malformations including microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies.

  The Zika virus was detected in Brazil last year and has since spread across the Americas. Singapore on Monday confirmed 15 new cases of locally transmitted infections, taking the tally to 56 as authorities step up efforts to contain the outbreak. 

Elsewhere, the U.S. Centers for Disease Control and Prevention, Australia, Taiwan and South Korea advised pregnant women and those attempting to get pregnant to avoid travel to Singapore.

Singapore's outbreak and the warnings come as a potential blow to tourism in one of the world's busiest travel hubs, which is already struggling to recover from a slump amid tepid global growth.

Singapore reported its first case of locally-transmitted Zika at the weekend, and the number of reported infections of the mosquito-borne virus has since jumped to 56. At least three dozen of those have since made a full recovery.

Screening in Southeast Asia

In most people infected with Zika virus, the reaction is mild, and 80 per cent have no symptoms.

The Zika virus was detected in Brazil last year and has since spread across the Americas. It poses a risk to pregnant women because it can cause severe birth defects. It has been linked in Brazil to more than 1,800 cases of microcephaly, a rare birth defect where babies are born with abnormally small heads and brains.

 The 56 confirmed cases in Singapore include only one woman.

Taiwan, Australia and South Korea advised pregnant women and those planning pregnancy to postpone trips to Singapore. Those returning from the country should avoid pregnancy for two months. South Korean travellers will receive text messages with the warning when they arrive in Singapore.

Regional health experts said the Zika virus is likely to be significantly under-reported across tropical Southeast Asia as 
local health authorities fail to conduct adequate screening.

As of Aug. 25, 232 travel-related cases, two sexually transmitted cases and three reports of maternal-to-fetal transmission have been detected in Canada.

There have been no reported cases of individuals infected by mosquitoes in Canada. Travellers are advised to take precautions against mosquito bites at all times.

With files from Reuters and CBC News


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