The new engl and jour nal of medicine n engl j med nejm.org 1 Brief Report Family Cluster of Middle East Respiratory Syndrome Coronavirus Infections Ziad A. Memish, M.D., Alimuddin I. Zumla, M.D., Ph.D., Rafat F. Al-Hakeem, M.D., Abdullah A. Al-Rabeeah, M.D., and Gwen M. Stephens, M.D. From the Global Center for Mass Gather- ings Medicine (Z.A.M., A.I.Z., R.F.A.-H., A.A.A.-R., G.M.S.), the Ministry of Health (Z.A.M., R.F.A.-H., A.A.A.-R., G.M.S.), and Al-Faisal University (Z.A.M.) — all in Riyadh, Saudi Arabia; and the Division of Infection and Immunity, University Col- lege London, and Department of Medical Microbiology, UCL Hospitals NHS Foun- dation Trust, London (A.I.Z.). Address re- print requests to Dr. Memish at WHO Collaborating Center for Mass Gathering Medicine, Ministry of Health, Riyadh 11176, Saudi Arabia, or at