Mosquitoes have infected two women with the Zika virus in Vietnam, the health authorities said on Tuesday, in the country's first cases of a disease linked to thousands of cases of the rare birth defect microcephaly in Brazil.
A 64-year-old woman in the beach city of Nha Trang and a pregnant 33-year-old in Ho Chi Minh City fell sick in late March and three rounds of tests have confirmed they are Zika-positive, health officials said.
The sufferers are in stable condition and no further infections have been found among their relatives and neighbours, Vietnam's Health Ministry said in a statement.
"After epidemic investigations, we consider the source of infection could be mosquito," Deputy Health Minister Nguyen Thanh Long said of the patient in Ho Chi Minh City.
She is eight weeks pregnant, Long said in a Vietnam Television broadcast, but gave no details regarding the first woman.
Health officials have quarantined the living areas of the patients' families and taken samples from others living nearby for further tests, said Nguyen Chi Dung, head of Ho Chi Minh City's department of preventive medicine.
The World Health Organization is working closely with Vietnam. A WHO official told the Health Ministry to announce the infections.
Zika is carried by mosquitoes, which transmit the virus to humans.
The WHO says there is a strong scientific consensus that Zika can cause microcephaly as well as Guillain-Barre syndrome, a rare neurological disorder that can result in paralysis, though conclusive proof may take months or years.
Microcephaly is a condition in which babies are borb with unusually small heads that can result in developmental problems.
The Zika virus has spread in Asia, with infection cases confirmed in Bangladesh, South Korea, Thailand and China.
Brazil said it had confirmed more than 860 cases of microcephaly in children, most of which it considers to be related to Zika infections in their mothers. It is investigating more than 4,200 additional suspected cases of microcephaly.