( ( 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 (NP (NNS Bacteria)) (, ,) (NP (NNS viruses)) (, ,) (NP (NNS fungi)) (, ,) (CC and) (NP (NN protozoa))) (VP (VBP are) (NP (NP (NNS examples)) (PP (IN of) (NP (NP (DT a) (NN pathogen)) (, ,) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (DT a) (JJ disease-causing) (NN microorganism)))))))) (. .)))