Respiratory viruses of human origin infect wild apes across Africa, sometimes 
lethally. Here we report simultaneous outbreaks of two distinct human 
respiratory viruses, human metapneumovirus (MPV; Pneumoviridae: Metapneumovirus) 
and human respirovirus 3 (HRV3; Paramyxoviridae; Respirovirus, formerly known as 
parainfluenza virus 3), in two chimpanzee (Pan troglodytes schweinfurthii) 
communities in the same forest in Uganda in December 2016 and January 2017. The 
viruses were absent before the outbreaks, but each was present in ill 
chimpanzees from one community during the outbreak period. Clinical signs and 
gross pathologic changes in affected chimpanzees closely mirrored symptoms and 
pathology commonly observed in humans for each virus. Epidemiologic modelling 
showed that MPV and HRV3 were similarly transmissible (R0 of 1.27 and 1.48, 
respectively), but MPV caused 12.2% mortality mainly in infants and older 
chimpanzees, whereas HRV3 caused no direct mortality. These results are 
consistent with the higher virulence of MPV than HRV3 in humans, although both 
MPV and HRV3 cause a significant global disease burden. Both viruses clustered 
phylogenetically within groups of known human variants, with MPV closely related 
to a lethal 2009 variant from mountain gorillas (Gorilla beringei beringei), 
suggesting two independent and simultaneous reverse zoonotic origins, either 
directly from humans or via intermediary hosts. These findings expand our 
knowledge of human origin viruses threatening wild chimpanzees and suggest that 
such viruses might be differentiated by their comparative epidemiological 
dynamics and pathogenicity in wild apes. Our results also caution against 
assuming common causation in coincident outbreaks.