Ebola virus (EBOV) causes a severe acute infection in humans [8] . Infection with the Ebola Zaire strain, Zaire ebolavirus (ZEBOV), produces mortality in the range of 60%-90% [9] with death generally occurring around 7-11 d following the appearance of symptoms [8] . There is a single report describing the use of convalescent sera to treat EBOV infection [10] . However, the patients in this report may have already been through the worst stages of the disease, and it is not clear that serum antibodies were responsible for their recovery [10] . Further, neutralizing antibody titers in survivors of EBOV infection tend to be rather low, although we have isolated a neutralizing human monoclonal antibody (mAb), KZ52, of good potency from a convalescent individual [11] .