Transmission from person to person
Infected people typically don't become contagious until they develop symptoms. Family members are often infected as they care for sick relatives or prepare the dead for burial.
Medical personnel can be infected if they don't use protective gear, such as surgical masks and gloves. Medical centers in Africa are often so poor that they must reuse needles and syringes. Some of the worst Ebola epidemics have occurred because contaminated injection equipment wasn't sterilized between uses.
There's no evidence that Ebola virus or Marburg virus can be spread via insect bites.