Dengue has affected 400 people so far in West Bengal, though apparently the severity of the mosquito-borne viral disease is less than last year.
West Bengal Chief Secretary Amit Kiran Deb said Monday at least 400 dengue cases were reported so far, while two cases of chikungunya were confirmed.
Though the official death toll was said to be one, unofficial sources said more people had died.
The state government earlier confirmed that of the seven blood samples sent to the National Institute of Virology in Pune for detection of chikungunya virus, two had tested positive.
"The Elisa test conducted at NIV, Pune, has confirmed two chikungunya cases among the samples," D.K. Niyogi, director, School of Tropical Medicine, said here.
Official sources feared that more chikungunya cases could be detected in West Bengal.
The two who tested positive are residents of Ramchandrapur village under Baduria block of Kolkata's adjoining North 24-Parganas district.
According to official figures, about 1,500 people in about 15 villages in Baduria and Swarupnagar are down with fever. Official sources said more than 1,200 blood samples were sent to Pune for tests.
Chikungunya was first reported in Bengal 43 years ago.
Early this month, city mayor Bikash Bhattacharya had said that only 29 people in Kolkata were found affected by dengue with one death reported.
He had said the situation was not alarming, especially compared to the previous year when 1,000 people were affected and 12 deaths occurred.