The mosquito-borne Zika disease has become endemic in Vietnam after nine victims tested positive in five of the country’s provinces and cities, according to one health official.

The disease is now considered an epidemic in the Southeast Asian country after nine patients have become infected in five localities, Tran Dac Phu, head of the General Department of Preventive Medicine under the Ministry of Health, told Tuoi Tre (Youth) newspaper on Sunday.

According to a study by authorities in the south-central province of Khanh Hoa, the Zika virus is now carried by the Aedes aegypti mosquito, whose numbers are higher than those that carry the dengue virus.

The Ministry of Health is expected to make an announcement on the improved protection against the virus for local residents, especially pregnant women, on Monday, Phu said.

“Zika is not a severe disease but can have serious consequences for female patients expecting a baby as the virus can cause microcephaly in infants,” the health official warned.

Zika is caused by a virus transmitted primarily by Aedes mosquitoes, according to the World Health Organization (WHO).

People with the Zika virus can experience symptoms including mild fever, skin rashes, conjunctivitis, muscle and joint pain, malaise or a headache that normally lasts between two and seven days, 

The virus can be transmitted via two species of mosquitoes, the Aedes aegypti and the Aedes albopictus, both infamous for spreading dengue, chikungunya, and other viruses. 

The most recent cases in Vietnam were recorded in Ho Chi Minh City with two female patients, one living in District 2 and the other in District 12, both testing positive.

The other victims were diagnosed earlier this year, namely one woman in the southern province of Binh Duong on October 8, one in Nha Trang City in early April, and a male patient in the south-central province of Phu Yen on August 3.  

Four foreigners have also reported their infection during stays in the Southeast Asian country, including an Australian man in March, a Korean woman in May, a German woman and a Taiwanese man, both confirmed in September.