Some supected cases of dengue have been reported in Sunnambur village in the district, where there was a severe outbreak about six months back.
Health Department officials claimed they had taken the initiative to control spread of the mosquito borne disase by disinfecting the area.
Reports said some people had been affected by leptospirosis, caused by rat urine, but were tested for dengue as officials said they did not want to take chances.
Initial tests were conducted on four persons near Thiruvadavur for leptospirosis and two others for dengue.
Officials said they are taking steps to prevent an outbreak in Sunnambur and neighbouring villages.