Answer:
Where do they occur: infected blood, semen or vaginal secretions in your body
How do they start: mainly by having s3x
How do they spread: either by s3x or injection drug use
How deadly are they: takes about 10 years for an injection to develop aids so idk a long time I guess? Just say very deadly
Is there a vaccine: not yet but people are working on some
Step-by-step explanation: