Crimean-Congo hemorrhagic fever virus (CCHFV) is a widely distributed 
hemorrhagic fever virus found throughout Eastern Europe, Africa, the Middle East 
and Asia. It is spread through bites from infected ticks, animal husbandry and 
can also be acquired in the healthcare setting during care of infected patients. 
In humans, CCHFV can cause a sudden onset of a non-specific febrile illness that 
can rapidly progress to severe hemorrhagic manifestations. Currently, there is 
no widely available vaccine and although ribavirin has been suggested for the 
treatment of CCHFV, clinical efficacy in both animal models and humans is 
inconsistent suggesting more potent antivirals are needed for CCHFV. Favipiravir 
is approved in Japan for the treatment of influenza virus infections and has 
shown promise against other highly pathogenic RNA viruses including CCHFV with 
demonstrated efficacy in the type I interferon deficient mouse model. In this 
report we utilized the cynomolgus macaque model to evaluate the efficacy of 
once- and twice-daily favipiravir treatment against CCHFV infection. We found 
that favipiravir treatment suppressed viremia and viral shedding when treatment 
was initiated 24 h post-infection and viral burdens in key tissues trended lower 
in favipiravir-treated animals. Our data indicate that favipiravir has efficacy 
against CCHFV in vivo in a non-human primate model of infection.