( ( By ( ( the middle ) ( of ( the ( 20th century ) ) ) ) ) ( , ( ( ( ( ( ( heart disease ) ( had ( ( surpassed ( infectious disease ) ) ( as ( ( the ( leading cause ) ) ( of ( death ( in ( the ( United States ) ) ) ) ) ) ) ) ) ) , ) and ) ( it ( ( is currently ) ( ( the ( leading cause ) ) ( of ( deaths worldwide ) ) ) ) ) ) . ) ) )
(ROOT (S (PP (IN By) (NP (NP (DT the) (NN middle)) (PP (IN of) (NP (DT the) (JJ 20th) (NN century))))) (, ,) (S (NP (NN heart) (NN disease)) (VP (VBD had) (VP (VBN surpassed) (NP (JJ infectious) (NN disease)) (PP (IN as) (NP (NP (DT the) (VBG leading) (NN cause)) (PP (IN of) (NP (NP (NN death)) (PP (IN in) (NP (DT the) (NNP United) (NNPS States)))))))))) (, ,) (CC and) (S (NP (PRP it)) (VP (VBZ is) (ADVP (RB currently)) (NP (NP (DT the) (VBG leading) (NN cause)) (PP (IN of) (NP (NP (NNS deaths)) (ADVP (RB worldwide))))))) (. .)))
By the middle of the 20th century, heart disease had surpassed infectious disease as the leading cause of death in the United States, and it is currently the leading cause of deaths worldwide.
(ROOT (S (NP (NNP Heart) (NN disease)) (VP (VBZ is) (NP (NP (DT the) (VBG leading) (NN cause)) (PP (IN of) (NP (NN death))) (PP (IN in) (NP (DT the) (VBN united) (NNS states))))) (. .)))