HANOI (REUTERS) - Two Vietnamese women have contracted the Zika virus which has been linked to thousands of suspected cases of microcephaly, a rare birth defect, in Brazil, and are the first Zika infections in Vietnam, the Health Ministry said on Tuesday (April 5).

A 64-year-old woman in the beach city of Nha Trang and another woman, 33, in Ho Chi Minh City fell sick in late March, and three rounds of tests have confirmed they are Zika-positive, the ministry said in a statement.

The two patients are in stable condition while no further infections among their relatives and neighbours have been found, the ministry said.

Zika is carried by mosquitoes, which transmit the virus to humans. Zika has not been proven to cause microcephaly in babies, but there is growing evidence that suggests a link. The condition is defined by unusually small heads that can result in developmental problems.

Brazil said it has confirmed more than 860 cases of microcephaly, and considers most of them to be related to Zika infections in the mothers.

Brazil is investigating more than 4,200 additional suspected cases of microcephaly.