Gray GC, Capuano AW, Setterquist SF, Erdman DD, Nobbs ND, Abed Y, Doern GV, Starks SE, Boivin G. Multi-year study of human metapneumovirus infection at a large US Midwestern Medical Referral Center. J Clin Virol. 2006 Dec; 37(4):269-76.