BANGKOK, Sept. 5 (Xinhua) -- Two pregnant women from northern Thailand's Chiang Mai were confirmed with Zika virus infection, leaving the number of Zika patients in the province at 11, local media reported on Monday.
Disease control officials in Chiang Mai stated on Monday that the Zika tests on the last two patients were confirmed positive on Saturday.
The two latest patients are a six-month pregnant Thai and an eight-month pregnant Myanmar woman. Both are living in the same district San Sai Luang, where nine Zika cases were recorded within a month.
Zika is a dengue-like virus transmitted by Aedes mosquitoes. It often occurs without symptoms and is usually mild and short-lived, making it difficult for pregnant women to know whether they have been infected.
A possible link between exposure to it in pregnancy and microcephaly -- resulting in babies with small heads and potential neurological damage -- and other congenital malformations has been identified.
According to the Public Health Ministry, 97 Zika cases were reported in Thailand from January to the end of June, compared with an average of five to seven each year in the past.
Sopon Mekthon, permanent secretary of the Public Health Ministry, said four provinces including the famous tourist destination Chiang Mai, are on the Zika transmission watch list, where 20 new cases have been reported since last week.
Officials have played down Zika outbreak fears, saying that an increase in the number of infected patients reflects the country's improved screening procedures and growing awareness among health workers.
However, the World Health Organization has listed Indonesia, Thailand, the Philippines and Vietnam as countries with "possible endemic transmission or evidence of local mosquito-borne Zika infections in 2016."
