For each ward, 15 to 20 motorbikes have been mobilised to spray mosquito-killing chemicals during the daytime. From 1am to 5am, the spraying is done by automobiles. The work will go on till the end of August. In addition, campaigns have been launched in recent days to clean surroundings to prevent the spread of mosquitos and larvae. These are part of the efforts of the Hanoi People's Committee to control the dengue fever outbreak and the increasing number of dengue patients.