The health department has stepped up surveillance after two persons -- man and a woman -- in the Sigur plateau in the Nilgiris tested positive for dengue recently.
Health officials have set up a medical camp in the area to test people complaining of illnesses that are symptomatic of dengue, which is caused by a virus transmitted by Aedes aegypti mosquitoes.
Deputy Director of Health Services S. Porkudi The Hindu that as both the patients had a travel history they could have contracted the virus from outside the Nilgiris.
While the man was a driver who regularly travelled to Karnataka, the woman attended a wedding outside the district, said Dr. Porkudi.
In the tests done during the camp that was on for over 10 days, all the patients had tested negative for dengue. Only a few cases of respiratory problems were found.
The health department had also collected larvae samples to check for the presence of the Aedes aegypti mosquitoes, an official said.
The mosquito breeds in stagnant fresh water. Officials said that these mosquitoes did not usually breed in the Nilgiris because of the climatic condition.
It breeds only in the Gudalur region, and that only during summer.
The officials also pointed out that with continuous rain, stagnation of fresh water was not possible and this ruled out Aedes aegypti breeding in the Nilgiris.
