Low risk of Zika-related birth defects, say doctors

SINGAPORE — The links between Zika infection and birth defects in babies could be blown out of proportion, some doctors suggest, stressing that no scientific association has been drawn between the mosquito-borne virus and microcephaly, a condition where a baby is born with an abnormally small head.

Reiterating that the risk of microcephaly ranges between 1 and 13 per cent, experts such as infectious disease specialist Leong Hoe Nam, who is based in Mount Elizabeth Novena Hospital, said that risk levels for Singapore is likely to fall within the lower end.

The “extremely high rate” of Zika-hit pregnancies that result in newborns with deformities in Brazil — the epicentre of an epidemic that is now in 45 countries and territories worldwide — is an “outlier”, Dr Leong said.

The first alarms about microcephaly were raised last October, when doctors in the state of Pernambuco in north-eastern Brazil reported a surge in babies born with it. By the following month, 646 such births were reported in the state alone and Brazil declared a health emergency, Reuters reported in April.

Between 2001 and 2014, Brazil had, on average, about 163 cases of microcephaly a year.

In contrast, a retrospective study of French Polynesia’s outbreak between 2013 and 2015, published in the United Kingdom medical journal The Lancet, puts the risk of microcephaly at closer to 1 per cent.

Even in Colombia — the country second-most affected by the virus — updates from the World Health Organisation showed in July that the number of microcephaly births there stands at 21, despite recording nearly 100,000 Zika-positive cases.

Dr Leong said that the “disproportionately high” rates of microcephaly in Brazil could be due to environmental and cultural factors.

Agreeing, Dr Beh Suan Tiong, an obstetrics and gynaecology specialist, pointed to suggestions that a new pesticide introduced into water supplies in Brazil to curb the development of mosquito larvae may be a culprit.

Dr Beh, who operates his own practice at Thomson Medical Centre, said: “Most countries reported (just) 2 to 3 per cent of babies affected. Brazil is the only one which reported a higher percentage. Obviously, there is something wrong with their data ... There must be some other factors apart from Zika that may have aggravated the situation (there).”

Microcephaly may be caused by a wide spectrum of factors, including rubella, consumption of anti-epileptic drugs and alcohol abuse.

“If you don’t test for all, you cannot be 100 per cent sure it is due to Zika,” obstetrics and gynaecology specialist Dr Christopher Chong said.

Although some doctors have said that there is no reason to delay pregnancy during the Zika outbreak, experts interviewed by TODAY said that the epidemic may cause a dent in the country’s already-low birth rate.

“People are getting worried, especially those just married, and they may try not to get pregnant in the meantime. But a lot depends on how the virus spreads or is contained in the next few weeks,” Dr Chong said.

The experts acknowledge that it is difficult to draw deep inferences, given that Singapore is still in the “early days” of the infection. Dr Beh said: “We will probably need to wait for a couple more months, or years, before a clearer association can be established ... It will be especially when more countries, especially in Asia, start to report their numbers.”

Singapore is in a “good position” to shed light and establish trends in these areas, he added, given its recent widespread testing of suspected cases.

Associate Professor Joanne Yoong from the Saw Swee Hock School of Public Health agreed that “active case finding” should be seen as a strength of Singapore’s control programme.

“Interpreting the spike in cases is not straightforward ... Part of the high rate of discovery is due to the efforts of the authorities to uncover otherwise hidden cases,” she said.