Vietnamese health officials confirmed the nation's third case of the Zika virus on Wednesday.
Nguyen Thi Mong Ngoc, Director of the Health Department of Phu Yen Province, said a 27-year-old man identified only as Hung had contracted Zika.
Hung was admitted to a hospital in Phu Yen on June 30th with symptoms including fever and rash. He recovered and was discharged from the hospital on Jul. 7.
However, a test had been performed on him and it came back positive on Jul. 28, according to a report by the health department.
Doctors are investigating how Hung contracted the virus.
The health department of Phu Yen has beefed up surveillance to prevent a possible Zika outbreak in the area where Hung lives.
The Zika virus is transmitted by infected mosquitoes and can be passed by sexual partners. Most people won't experience the disease's mild symptoms, which include rash and joint pain, but health officials say Zika infections in pregnant women can cause severe birth defects.
Vietnam reported its first two Zika patients in April, a 64-year-old woman in Nha Trang and a 33-year-old woman in Ho Chi Minh City. The latter was then eight weeks pregnant but underwent an abortion after the ultrasound scan reportedly did not detect the fetal heartbeat.
A South Korean who stayed in HCMC for 20 days was also diagnosed with the virus after she returned home in May.