( ( These ( new viruses ) ) ( then ( ( spread ( to ( infect ( other cells ) ) ) ) . ) ) )
(ROOT (S (NP (DT These) (JJ new) (NNS viruses)) (ADVP (RB then)) (VP (VBD spread) (S (VP (TO to) (VP (VB infect) (NP (JJ other) (NNS cells)))))) (. .)))
These new viruses then spread to infect other cells.
(ROOT (S (NP (NNP Tamiflu)) (VP (VBZ inhibits) (NP (NP (NN spread)) (PP (IN of) (NP (NN virus))))) (. .)))