Scores of people suffering with the crippling fever, Chikungunya, have been reported from West Bengal's North 24 Pargana District.
Twenty-one of the 36 samples that were earlier sent to the Indian Council for Medical Research (ICMR) have tested positive.
'Chikungunya' virus spreads through mosquito-bite and causes a non-fatal self-limiting illness, marked by high fever, headache, severe joint pain, rashes and nausea.
Health officials are working over-time in the region to provide assistance and curb the spread of disease.
Medical camps have been set up and health workers are taking precautionary measures like spraying disinfectants in villages. Health workers are also carrying out door-to-door visits to keep a check on patients.
'Our health staff and doctors are visiting houses and identifying the cases and accordingly we are giving priority in treating the patients,' said Kusum Kumar Adhikari, Health Officer.
The outbreak has caused an alarm in the region.
'We are really terrified,' said Padma Sarkar, a villager.
Like dengue, another mosquito borne disease, there is no vaccine for Chikungunya, and at best, symptoms can be countered through painkillers, intake of plenty of fluids and lots of rest.
Chikungunya, first reported in India in Kerala in 2000, has taken a toll of several hundred lives. Thousands were admitted to hospitals across the State since May this year that followed the southwestern monsoon.