Chou Chih-hau, deputy director-general of the DOH’s Center for Disease Control (CDC), said the cluster infection in Tainan was the largest in nearly 10 years.

The first case of the cluster infection was reported Aug. 8, followed by more cases Aug. 13 and 14. Tainan City’s Health Bureau and the CDC then started examinations of residents and inspected the environment around the veterans’ home, which houses more than 400 veterans in their 70s or 80s.

The CDC discovered that 44 residents were infected with dengue fever and found that drains on the roof and water reservoirs of the facility’s air conditioners were the main mosquito breeding areas.

Chou said elderly people infected with dengue fever do not show obvious symptoms of rash and high fever of up to 39 degrees Celsius. He reminded nursing houses to heed the situation and clean water storage containers around residences to avoid another cluster infection.

Chou said the North District of Tainan City also reported its second indigenous dengue fever case — a two-year-old girl who was diagnosed with the disease Aug. 6. She was discharged from the hospital Aug. 17.

Meanwhile, Kaohsiung County officials responsible for health and environmental protection affairs were mobilized for an urgent undertaking aimed at preventing an outbreak of dengue fever.

County Magistrate Yang Chiu-hsiung ordered officials to reinforce efforts to cleanse mosquito-breeding sites after the southern county reported last week its first indigenous dengue fever case this summer.

The patient, a woman aged over 50, resides in the county’s Fengshan City but works in the neighboring city of Kaohsiung, County Director of Health Huang Chih-chung said, noting that Kaohsiung City is one of southern Taiwan’s dengue-affected areas, with 52 cases of indigenous dengue fever reported so far since the beginning of the summer.

Dengue fever, a viral illness, is manifested by the sudden onset of fever, severe headache, muscle and joint pains, and skin rash. The classic dengue fever lasts about six to seven days, with a smaller peak of fever at the trailing end of the fever. It can be deadly when the patient is infected by the hemorrhagic dengue fever.