viruses Review An Opportunistic Pathogen Afforded Ample Opportunities: Middle East Respiratory Syndrome Coronavirus Ian M. Mackay 1,2,* ID and Katherine E. Arden 2 1 Public and Environmental Health Virology, Forensic and Scientific Services, Department of Health, Queensland Government, Coopers Plains, 4108 QLD, Australia 2 Child Health Research Centre, The University of Queensland, South Brisbane, 4101 QLD, Australia;