Indoor ndoor and and Built uilt Environment Original Paper Ventilation of general hospital wards for mitigating infection risks of three kinds of viruses including Middle East respiratory syndrome coronavirus H.C. Yu, K.W. Mui, L.T. Wong and H.S. Chu Abstract This study investigates the effectiveness of ventilation design strategies for general hospital wards in terms of virus removal capacity. A typical semi-enclosed six-bed general ward of Hong Kong hospitals and three respiratory viruses, namely Middle East respiratory syndrome coronavirus (MERS-CoV), severe acute respira- tory syndrome coronavirus (SARS-CoV) and H1N1 influenza virus, were chosen for the computational fluid dynamics (CFD) simulation of airflow field and virus dispersion inside the ward. The results demonstrated that the location of an infected patient would affect the infection risks to other occupants and healthcare workers inside the same hospital ward, and an increased air change rate in the ward could reduce the risk of infection from direct contact and inhalation. It was found that an air change rate of 9h�1 could effectively minimize the deposition and floating time of respiratory virus particles while maximizing energy efficiency. This study should provide a useful source of reference for the hospital management to mitigate the risk of infection with MERS or other airborne transmitted viruses through better ventilation design strategies. Keywords Ventilation, Virus dispersion, Hospital general wards, CFD, Middle East respiratory syndrome (MERS) Accepted: 4 January 2016 Introduction According to a statistical report by the Hong Kong Hospital Authority,1 the in-patient discharges and deaths were continuously increasing from 2003 to 2013. The 2012/2013 overall number of in-patient dis- charges and deaths was 1,027,005, and that of day- patient was 516,127 in Hong Kong. Among all patients, 33.4% were day-patients. To prevent nosocomial or healthcare-associated infections, especially airborne ones, hospital hygiene and infection control are necessary. The Centres for Disease Control and Prevention (CDC) provides guid- ance to help healthcare personnel to follow standard, contact, and airborne precautions when caring for hos- pitalized patients with known or suspected viral infec- tions.2 Effective prevention measures, e.g. an airborne infection isolation room (AIIR), are especially crucial for control of acute respiratory infectious threats. Proper ventilation also plays a key role in infection control by minimizing airborne bacteria and viruses. Both the spread of severe acute respiratory syndrome coronavirus (SARS-CoV) during the largest nosoco- mial SARS outbreak in Hong Kong and the recent out- break of Middle East respiratory syndrome (MERS) in the South Korean hospitals revealed that airborne dis- ease transmission through inefficient hospital ward ven- tilation systems can lead to dire health consequences.3–5 For a balanced ventilation that delivers indoor air Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China Corresponding author: L. T. Wong, Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China. Email: