The Ministry of Health has beefed up surveillance to prevent a possible Zika outbreak in Ho Chi Minh City’s District 7, where a South Korean had stayed for 20 days and was diagnosed with the virus when she returned home.
A statement from the ministry said the 25-year-old woman worked from April 10 to 30 at an international school in District 7 and stayed at an apartment building in Phu My Hung urban area in the district.
The ministry said it would monitor the school and apartment and find out if anyone was in close contact with her.
The city health department and the Pasteur Institute have also beefed up surveillance of the areas.
The woman returned home on May 1 and tested positive for Zika on May 7, three days after she went to a local hospital with rashes and joint pain.
Health officials in South Korea suspect that she was bitten by mosquitoes in Vietnam and contracted the virus, which has an incubation period of three to 12 days. They are also checking a person who met her during her stay in Vietnam.
The Aedes aegypti mosquito, the main vector of the virus, is very common in Vietnam. It is also known for carrying the dengue, yellow fever and chikungunya viruses.
Vietnam reported its first two Zika patients last month, a 64-year-old woman in Nha Trang and a 33-year-old woman in HCMC. The latter was then eight weeks pregnant but underwent an abortion after the ultrasound scan reportedly did not detect the fetal heartbeat.
No further infections have been reported since.
Zika was first detected in Africa in 1947 and has been considered a relatively mild disease until the current outbreak started in Brazil in May 2015.
The disease has since spread to more than 60 countries and territories, including many in Southeast Asia such as Indonesia, Laos, Malaysia, the Philippines, Thailand, and South Korea.
Brazil, Venezuela and Columbia have each reported three deaths linked to the Zika virus.
Brazil has reported nearly 5,000 confirmed and suspected cases of microcephaly associated with Zika, Reuters reported.