Vietnam's Ho Chi Minh City on Friday declared a Zika case at a ward scale, the municipal Health Department announced.

The declaration was made after a 33-year-old woman from the city's District 2 had been found infected with Zika virus.

Earlier, Nha Trang city in central Khanh Hoa province confirmed a Zika case after a 64-year-old woman from the city's Phuoc Hoa district had been tested positive to the virus.

Since the first two Zika patients were confirmed in Vietnam on Tuesday by the country's Health Ministry, Ho Chi Minh City, Nha Trang City and many other localities nationwide have strengthened disease prevention and fight, including cleaning environments and exterminating mosquitoes' larvae in residential areas.

Zika virus disease is caused by a virus transmitted by Aedes mosquitoes. People with Zika virus disease usually have symptoms that include mild fever, skin rashes, conjunctivitis, muscle and joint pain, malaise or headache.