Students in Roseburg and Oakland were sickened last month by identical strains of norovirus, health officials said Wednesday. The fast-moving illness, which causes diarrhea and vomiting, swept through Fir Grove Elementary School in Roseburg in early November. Health officials say it was probably transmitted through the community and reached the Oakland School District’s K-12 campus two weeks later. Stool specimens collected at the schools were tested by the Oregon State Public Health Laboratory in Hillsboro following the outbreaks. The Oakland and Fir Grove samples were found to be at least 99 percent identical, Douglas County Environmental Health Specialist Caroline Regan …