( Viruses ( ( are ( extremely ( effective ( at ( infiltrating cells ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Viruses)) (VP (VBP are) (ADJP (RB extremely) (JJ effective) (PP (IN at) (S (VP (VBG infiltrating) (NP (NNS cells))))))) (. .)))
Viruses are extremely effective at infiltrating cells.
(ROOT (S (NP (NNP Tamiflu)) (VP (VBZ inhibits) (NP (NP (NN spread)) (PP (IN of) (NP (NN virus))))) (. .)))