S1-CTD hACE2- Nov 2002–Jan 2003 (early epidemic, HP, animal/human-to-human by close contact): viral S gene contains 17–22 SNVs. - Feb–Jul 2003 (epidemic, HP, human-to-human by close contact): 25–27 SNVs- Dec 2003–May 2004 (re-appearance, LP, animal-to-human): 2–7 SNVs