MIAMI, United States (AFP) — Four times the number of babies born with skull deformities linked to Zika virus were reported in Colombia this year following the outbreak of the mosquito-borne infection, said a United States Government report last Friday.

Women infected early in pregnancy were most at risk of giving birth to babies with unusually small heads, a condition known as microcephaly, said the report by the US Centers for Disease Control and Prevention (CDC).

The Zika outbreak, which began in mid-2015, has mainly swept across Latin America and the Caribbean. The viral disease can be spread by the bite of an infected Aedes mosquito or sexual contact.

The toll of microcephaly in Colombia was smaller than in Brazil, which saw a ninefold increase in the disorder, perhaps because much of the population in Colombia lives at higher elevations where mosquitoes are scarce, according to the report.

“This preliminary report on Zika virus disease and microcephaly in Colombia demonstrates that an increase in microcephaly is not specific to Brazil,” the CDC said.

“This finding confirms that countries with Zika virus outbreaks are likely to experience large increases in microcephaly and other Zika-related birth defects.”

Colombia saw 476 cases of microcephaly from January 31 to mid-November 2016, said the CDC report, four times higher than the same period a year earlier.

Of those cases, 432 infants were born alive and 44 were lost to either miscarriage, abortion, or stillbirth.

“The peak in cases of microcephaly in Colombia came about six months after the period in which the highest number of new Zika infections was reported, which suggests that the highest risk period for Zika-associated microcephaly is likely to be in the first half of pregnancy, particularly the first trimester and early in the second,” the CDC said.

Colombia reported a total of 105,000 cases of Zika virus, including nearly 20,000 cases in pregnant women, from August 9, 2015 through November 26, 2016.

Zika has spread through 69 countries from 2015 onward, and 29 nations have reported birth defects possibly linked to the viral infection, according to the World Health Organization.