By Gradel Muyisa, Emma Farge, Clement Bonnerot and Ammu Kannampilly BUNIA, Democratic Republic of Congo, June 19 (Reuters) - At least 30 people have died since the start of May in one camp for displaced civilians in northeastern Congo, a death rate that camp officials said was unprecedented, with some confirmed to have died from Ebola in a sign the disease could be spreading fast there.