( ( The ( term ( disease ( causative agent ) ) ) ) ( usually ( ( refers ( to ( ( ( ( the ( biological pathogen ) ) ( that ( causes ( a disease ) ) ) ) , ) ( such ( as ( ( ( a virus ) , ) ( parasite ( , ( fungus ( , ( or bacterium ) ) ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (DT The) (NN term) (NN disease) (NN causative) (NN agent)) (ADVP (RB usually)) (VP (VBZ refers) (PP (TO to) (NP (NP (DT the) (JJ biological) (NN pathogen)) (SBAR (WHNP (WDT that)) (S (VP (VBZ causes) (NP (DT a) (NN disease))))) (, ,) (PP (JJ such) (IN as) (NP (NP (DT a) (NN virus)) (, ,) (NP (NN parasite) (, ,) (NN fungus) (, ,) (CC or) (NN bacterium))))))) (. .)))
The term disease causative agent usually refers to the biological pathogen that causes a disease, such as a virus, parasite, fungus, or bacterium.
(ROOT (S (NP (NNS Pathogens)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (JJ disease-causing) (NNS agents))) (, ,) (PP (JJ such) (IN as) (NP (NNS bacteria) (CC and) (NNS viruses))))) (. .)))