ABSTRACT
Between 19 April and 23 June 2015, 52 laboratory-confirmed cases of Middle East Respiratory Syndrome due to coronavirus [MERS] were reported from Al-Ahssa region, eastern Saudi Arabia. The first seven cases occurred in one family; these were followed by 45 cases in three public hospitals. The objectives of this investigation were to describe the epidemiological characteristic of the cluster and identify potential risk factors and control measures to be instituted to prevent further occurrence of MERS. We obtained the medical records of all confirmed cases, interviewed the members of the affected household and reviewed the actions taken by the health authorities. All the cases were connected. The index case was a 62-year-old man with a history of close contact with dromedary camels; three of the seven infected family members and 18 people in hospitals died [case-fatality rate, 40.4%]. The median incubation period was about 6 days. The cluster of cases appeared to be due to high exposure to MERS, delayed diagnosis, inadequate risk communication and inadequate compliance of hospital health workers and visitors with infection prevention and control measures