Unlike Conventional AIDS, which is transmitted through blood, The Cancerous strand can be transmitted through any bodily fluid. This means if a CAIDS infected person was to cough in your general direction, and you happened to be taking a breath, the virus could be transmitted to you in an airborne contraction situation. Taking a drink after, or kissing an infected person can also lead to transmission.
Obviously this is some shit you dont want to get, and any individual infected must be quaranteened immediately. An infected person in a situation such as a subway ride, could potentialy infect hundreds if not thousands of people in a matter of an hours.