Each patient of each cohort will receive favipiravir loading doses of 4800 mg at Day 1 (2400 mg bid), following by 3600 mg (1800 mg bid) from Day 2 to 14 (cohort 1), then 3600, 4200 or 4800 mg from Day 2 to 14 (cohort 2 and 3), depending on previous cohort results.