Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA

Correspondence to William W. Busse, MD, Emeritus Professor of Medicine, University of Wisconsin Hospital, K4/910 CSC, MC 9988, 600 Highland Avenue, Madison, WI 53792, USA. Tel: +1 608 263 6183; e-mail: [email protected]