A total of 14 people, all but one of whom are foreign workers, fell ill last month and were found to have malaria. One full-time national serviceman was also among the clusters. Twelve of them have been discharged as of last Saturday.

All 14 patients, aged between 20 and 40, had no recent travel history, leading the MOH to suspect that there is local malaria transmission in the areas.

Malaria, like dengue fever, is a mosquito-borne disease. It is spread by the Anopheles mosquito.

The National Environment Agency (NEA) has inspected the worksites, dormitories and its surrounding areas. The agency is conducting adult-mosquito trapping and search-and-destroy operations. NEA has also asked the dormitory operators to carry out measures to rid the area of mosquitoes.

The last local malaria cases were in 2007 when there were also two clusters - one involving three NS men and the other involving two Redhill residents.