BACKGROUND: The Middle East respiratory syndrome coronavirus (MERS-CoV) has been reported to have a high case-fatality rate. Currently, there is no specific therapy or vaccine with proven effectiveness for MERS-CoV infections. METHODS: A combination of ribavirin and interferon therapy was used for the treatment of five MERS-CoV-positive patients. We reviewed the therapeutic schedule and the outcome of these patients. RESULTS: All patients were critically ill with acute respiratory distress syndrome treated with adjunctive corticosteroids and were on mechanical ventilation at the time of initiation of therapy. The median time from admission to therapy with ribavirin and interferon was 19 (range 10-22) days. None of the patients responded to the supportive or therapeutic interventions and all died of their illness. CONCLUSIONS: While ribavirin and interferon may be effective in some patients, our practical experience suggests that critically ill patients with multiple comorbidities who are diagnosed late in the course of their illness may not benefit from combination antiviral therapy as preclinical data suggest. There is clearly an urgent need for a novel effective antiviral therapy for this emerging global threat.