WASHINGTON (REUTERS) - Two US soldiers serving in South America contracted Zika but have fully recovered and returned to duty, while a third, pregnant service member left the region early for fear of contracting the virus, a top US commander said on Thursday (March 10).

Zika infections have been linked to thousands of birth defects as the mosquito-borne virus spreads rapidly in Brazil and other countries in Latin America and the Caribbean.

Two US servicemen stationed in Brazil and Colombia were confirmed to have contracted Zika, said Navy Admiral Kurt Tidd, commander of US Southern Command.

"Both cases were confirmed. The cases have (been) resolved," he said in a news briefing. "They both returned to duty."

A third, pregnant service member in the region sped up her scheduled return to the United States as a result of the Zika scare, Adm Tidd said.

The US military has discussed mosquito eradication with partner militaries in the region and has provided small amounts of supplies, including mosquito netting, he said.

Much remains unknown about Zika, including whether the virus actually causes microcephaly in babies, a condition defined by unusually small heads that can result in developmental problems.

On March 9, Brazil said confirmed microcephaly cases rose to 745 and considers most of them to be related to Zika infections in the mothers. Brazil is investigating an additional 4,231 suspected cases of microcephaly.

Traces of Zika virus have been found in the bodily fluids and tissue of mothers and babies affected by microcephaly.