Ebola is spreading faster than responders can track it in eastern Congo, where health workers managed to follow up with barely one in five identified contacts in a single day.Authorities in the Democratic Republic of Congo (DRC) reported 83 confirmed infections, 746 suspected cases and 1,603 identified contacts as of May 21, according to the health ministry.Yet health workers were able to follow up with only 342 contacts that day – about 21 per cent of the total under monitoring – according to...