- Use of the P gene to genotype human metapneumovirus identifies 4 viral subtypes. Mackay, I.M., Bialasiewicz, S., Waliuzzaman, Z., Chidlow, G.R., Fegredo, D.C., Laingam, S., Adamson, P., Harnett, G.B., Rawlinson, W., Nissen, M.D., Sloots, T.P. J. Infect. Dis. (2004)