Mathematical projections suggest about 93.4 million people may catch the virus -- including some 1.65 million pregnant women -- before the epidemic fizzles out, a team reported in the journal Nature Microbiology.
Eighty per cent of people will develop mild symptoms or never even be aware they have the virus.
But for babies in the womb Zika can be devastating -- linked to a brain-damaging disorder called microcephaly that can lead to stillbirth or severely disabling birth defects.
This meant "somewhere on the order of tens of thousands across the whole of Latin America and the Caribbean who could realistically end up developing microcephaly or a related condition," said study co-author Alex Perkins of the University of Notre Dame in Indiana, and specified this referred to "live births."
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The projection was "a worst-case scenario" he told AFP, "but a realistic one".
It did not account for women who may be postponing conception or having abortions as a result of the outbreak.
The team used data on the usual number of pregnancies, the prevalence of the mosquito species spreading the virus, weather conditions and socio-economic conditions that make people more vulnerable, and disease spread dynamics.
Mathematical models of disease progression are notoriously prone to inaccuracies, as estimates can be skewed by such factors as the infectiousness of the virus, the adaptative response of the immune system and social and economic factors that help it to spread.
Derek Gatherer of Lancaster University noted recent research which found that as many as 29 per cent of babies of Zika-infected mothers develop problems.
If so, "over half a million" children may ultimately be affected, he said.
Whatever the final number, a support system for affected babies and their families "needs to be put in place as soon as possible," said Jimmy Whitworth of the London School of Hygiene & Tropical Medicine.
"Over 1,700 affected babies have been born in Brazil so far, and the numbers are going to continue to increase in the months ahead," he said in comments via the Science Media Centre.