OK, so this is an "urban legend". This is the reply to all those Craptower magazines that relate to people that narrowly missed getting AIDS from fornication, simply by staying within Tower principles.
This time, the brother refrained from fornication, though the person he was tempted with was just about perfect for him--except for religion. Instead, this brother devoutly passed her by and went from door to door trying to "do the right thing". This created quite a bit of emotional conflict for both parties.
One day, the brother knocked on a door. The person came to the door coughing a lot. No big deal: the flu is going around at this time of year. But a few weeks later, he notices that this is no ordinary flu. He goes to the doctor, and finds that he now has tuberculosis. And from all the exhausting service, it has gone active much quicker than normal. And it is much worse than normal.
Still, he is determined to go out in service. Coughing, he is soon infecting most of the congregation with tuberculosis. A number of people at the doors catch it too--however, they are not as severe since those people have the opportunity to sleep more. And with this grueling schedule, the tuberculosis gets much worse and soon this brother ends up dead. About 10 minutes before he dies, he finds out that his would-have-been girlfriend did NOT have AIDS or any of that sort of disease.
Now, one might ask how long one must go out in service to catch tuberculosis. It's not as long as it seems. I just heard that 4.2 people per 100,000 have it. Meaning you have to knock on 24,000 doors on average to run into one that has tuberculosis (the actual number is closer to 10,000 due to multi-person households and it only takes one to have it to catch it). If you are getting the door-a-minute that they "suggest", you will get 60 doors an hour. That is 600 per day, if you work the 10-hours they "suggest". Which works out to about 40 days of service on average before you are going to run into tuberculosis. That is about 400 hours, if you are industrious (if you are lazy or poorly organized, then of course it will take longer).
If you knock on doors like Jehovah's Witnesses do all the time, it's only a matter of time before you are going to be exposed to tuberculosis. And your resistance will be compromised from being exhausted from all that service, and the poor McPioneer diet that too many people eat (a Big Mac or Whopper for lunch every day and a quick TV Poison dinner for supper. Like the Craptower is quick to pounce on for AIDS and fornication, if you keep knocking on those doors, you ARE going to catch tuberculosis. It's only a matter of time.
And by the way, you won't even get the fun before catching the disease. At least with fornication, you get a bit of fun before paying for it. By going door to door, you lose out on even that. Plus you are as likely to spread a deadly plague. (No, tuberculosis is not easy to cure. And in the condition the Witnesses are in, it may well be impossible--even getting rid of the bacteria will still leave the body weak and open to other infections, and the schedule precludes getting any sleep to help.)