'Using a microscope, Paul Langerhans jump-started the islet research field when he visualized “. . . small cells of almost perfect homogeneous content & of a polygonal form, with round nuclei without nucleoli,mostly lying together in pairs or small groups” https://t.co/1Lwn1cqXQW https://t.co/dlGuzr66OG

"One way to do this is cluster investigations, or “backwards contact tracing”, which have been a key feature of the thus far successful response in Japan." Ref Cluster-based approach to COVID-19 response in Japan—February–April 2020 https://t.co/oFDi8D7EXD