A paper on the global spread of different genogroup II.4 variants hasa been published:

Norovirus illness is a global problem: emergence and spread of norovirus GII.4 variants, 2001-2007
Siebenga JJ, Vennema H, Zheng DP, Vinjé J, Lee BE, Pang XL, Ho EC, Lim W, Choudekar A, Broor S, Halperin T, Rasool NB, Hewitt J, Greening GE, Jin M, Duan ZJ, Lucero Y, O'Ryan M, Hoehne M, Schreier E, Ratcliff RM, White PA, Iritani N, Reuter G, Koopmans M.
J Infect Dis. 2009 Sep 1;200(5):802-12.