Eleven districts of Bengal have reported at least 65 cases of black fever or 'kala-azar' in the last couple of weeks, a senior official of the health department said, citing results of a state-administered surveillance.

The districts where maximum number of cases was registered include Darjeeling, Malda, Uttar Dinajpur, Dakshin Dinajpur and Kalimpong, he told PTI.

"Kala-azar was practically eradicated from West Bengal. A recent surveillance, however, led to the detection of 65 cases in 11 districts. Now that these cases have come to the fore, the state will be able to tackle the spread of the disease, the official said.

The districts of Birbhum, Bankura, Purulia, Murshidabad have also reported a few cases of black fever, mainly transmitted by bites of sandflies infected with the parasite leishmania donovani'.

According to the official, no case has yet been detected in Calcutta.

"It was found that the disease was mostly prevalent in people who have spent a considerable amount of time in Bihar, Jharkhand and in Uttar Pradesh. Some individuals from Bangladesh, too, have been showing symptoms of kala-azar," the official said, adding, the surveillance process will continue.

A top bureaucrat at the state secretariat said the government has taken the decision to treat all diagnosed with the disease "free of cost".

"Even if the infection is detected in a private laboratory or hospital, the doctor should immediately bring the matter to the attention of the district health officer. All expenses of treatment along with meals will be borne by the state health department. The district chief health officer will monitor the whole process," the bureaucrat told PTI.

Arrangements are also being made to provide nutritious food to the patients, he said.