WordNet sense 1 (a source of danger; a possibility of incurring loss or misfortune):

endangerment, hazard, jeopardy, peril

WordNet sense 2 (the probability of becoming infected given that exposure to an infectious agent has occurred):

risk of infection

WordNet sense 3 (the probability of being exposed to an infectious agent):

risk of exposure

WordNet sense 4 (expose to a chance of loss or damage):

lay on the line, put on the line

WordNet sense 5 (take a risk in the hope of a favorable outcome):

adventure, chance, gamble, run a risk, take a chance, take chances

WordNet sense 6 (a venture undertaken without regard to possible loss or injury):

danger