Hence, these results suggest that the seasonality of influenza A(H3N2) may, in fact, result from a combination of these 2 models postulated by Nelson et al [19] , i.e. mainly migration, but with occasional examples of latency. Again, due to the unavoidable, incomplete sampling and sequencing of influenza A(H3N2) viruses worldwide, this support for these hypotheses ('migration' and 'latency'), as presented here, is admittedly, only patchy at best. However, the fact that we can find at least one example supporting the latency hypothesis, in these 281 HA and NA sequences spanning 10 years (1997) (1998) (1999) (2000) (2001) (2002) (2003) (2004) (2005) (2006) , suggests that they may both play a part in the underlying mechanism governing influenza A(H3N2) seasonality.