In what can be termed as a Covid-19 blast as many as 18 students of National Institute for Empowerment of Persons with Visual Disabilities (NIEPVD) earlier NIVH were detected positive for the disease on Wednesday. The district surveillance officer of Dehradun Dr Rajiv Dixit said samples of 169 students were taken for testing and out of them reports of 138 had arrived. The NIEPVD authorities has imposed a ban on entry of outsiders in the campus