HO CHI MINH CITY, June 4 (Xinhua) -- Five more medical workers here have shown A/H1N1 influenza symptoms, raising the total suspected and confirmed cases to 28, including 16 confirmed ones, the municipal Preventive Medicine Center said Monday.

Of the 28 suspected cases, eight are medical workers at the Endoscopy Department of Tu Du Hospital, a major maternity institution in Vietnam, and 20 are patients at the hospital.

Last Friday, a woman from southern Tien Giang province went to the hospital for gynecological checkup.

Later on the same day, there were 23 cases of patients, their relatives and medical workers who had close contact with the woman simultaneously having high temperatures, a running nose and sore throat. Sixteen of them tested positive for A/H1N1 influenza, an acute respiratory disease.

According to the World Health Organization, the disease can be transmitted by droplets emanating from unprotected coughs and sneezes, hand contamination, and interpersonal encounters in crowded closed spaces.

In a tropical country like Vietnam, the influenza circulates the entire year round, usually reaching several peaks in the rainy season. The A/H1N1 virus causes pernicious respiratory infection.

Vietnam experienced an H1N1 pandemic in 2009, with over 9,000 cases of people contracting the disease and nearly 20 deaths within four months of the year, according to its Health Ministry.