CALCUTTA, April 22 (AP)— The West Bengal state government reported tonight that cholera and smallpox had broken out among nearly half a million refugees who had fled to India from East Pakistan.

The state commissioner for refugees, Benoy Mandal, ap pealed for foreign aid to meet the emergency.

Mr. Mandal told newsmen that 451,000 refugees had reached West Bengal. He said that 107,000 were being accommodated in emergency camps and that 344,000 were staying with relatives and friends.

In addition, 1,800 have crossed from into the Indian states of Assam and Meghalaya and 27,000 into Tripura, ac cording to Government figures.

“The situation is approaching the magnitude of a national disaster,” Mr. Mandal said. “It will cause a serious strain on India's national resources. But you may be assured that so long as we eat, so the refugees will eat.”