Estates in Bishan have been identified by the National Environment Agency (NEA) as a red alert area with a high number of dengue cases.
The two clusters identified from Bishan Street 22 to 25 have seen 247 cases since the start of the cluster. 49 cases have been reported in the two clusters in the past fortnight.
The NEA also issues preventive actions accompanying each alert level (green, yellow and red in order of seriousness).
Channel NewsAsia reported in June that warmer months tend to see an increase in the number of dengue cases.