Complex sentence: Often, infectious pathogens associated with a disease may be suspected of playing a causal role in that disease--though association does not automatically imply causation (see correlation does not imply causation).
Split into simpler sentences: Often, infectious pathogens associated with a disease may be suspected of playing a causal role in that disease. However, just because a pathogen is associated with a disease, it does not automatically imply that the pathogen causes the disease (since correlation does not imply causation).