I think you're a little over-worried (though I won't say paranoid) about it. However, I think your biggest worries aren't in blood-born disease, but rather, parasites and bacteria. Yes, you'll get colds and the like, but meningitis would be my biggest fear.
In anything you do, you rely on the sanitary habits of each and every person you come in contact with, as well as anyone who has been in your physical location in as far back in the past as a few hours, to keep you from getting sick.
That's a lot of people!
This morning, I watched a clerk cook someone's breakfast burrito: she pulled out a baggie from the fridge, opened it with bare hands, pulled out raw chicken, placed it on the griddle. She then grabbed a spice container and spiced up the chicken. Then she opened the fridge again pulled out a baggie of prepared shrimp, opened it, and placed it on the griddle. Another spice can. And a spatula. Then she grabbed onions and peppers from an open can and cooked them with the chicken and shrimp. She cooked eggs. She reached for a cheese slice. Then she finally reached for a tortilla shell - still all bare hands - wrapped it all up, and handed it to the customer, who gave her a $20 bill, and she returned cash for change. Next customer.
With hygiene like that, I have strong doubt she was conscientious enough to wash her hands after using the bathroom, but that is a strong assumption I'm making. Then again, all of the customers there were day laborers from a very poor country. It is likely their bodies' immune systems were already on high alert, and these guys weren't going to get sick from eating a full tablespoon of raw E Coli bacteria.
Everything you touch, you are at the mercy of someone else's hygiene. The lettuce in that salad you're eating? The birds overhead. The moles, voles, skunks, groundhogs, and squirrels. None of them have formal bathrooms, and a head of lettuce is just as comfortable to them as a rock. The lettuce pickers. The handlers on the assembly line. The baggers. The shelvers. The customer in the store who picked up the bag (and who is pushing a supermarket cart with bare hands), looked at the price, and decided to put it back down. You sure they ALL washed their hands and didn't cough over the assembly line?
The point is, the more exposure you have to microorganism, the less likely you are to become sick from it. Some microorganisms, like meningitis, are things I would be in absolute fear of; but with a body immune system on high alert from other microorganisms, I think that is less likely an issue.
With martial arts, there are many diseases and sicknesses you are exposed to - and blood-borne are but a few of them, and the most feared ones aren't blood-borne. Even people who ARE hygienic enough to wash their hands, they can still be carriers and not even know it.
You - everyone - should take reasonable steps to maintain good hygiene, like keeping clothes, uniforms, duffel bags, shoes, and training equipment clean; as well as regular showering, keeping nails short, etc.
At the same time, the place you train at - no matter the sport - needs to have good hygienic practices as well:
- It needs to periodically sterilize mats, floors, and other commonly accessed surfaces
- It needs to have a process in place for spilled blood, saliva, and vomit
- It needs to have an accessible first aid kit (which itself needs to be washed periodically), and that first aid kit needs to be accessible and stocked, but also, must not allow access to its contents to be contaminated from the very reason people go in there. So, band aids and sterile wipes should be loose, there should be gloves, and people need to be trained to use it properly. (That is to say, things within to be dispensed should be dispensed by someone who is not injured).
Also, the place you train at needs to understand its role in the microbial ecosystem, as it is a new vector for people to become sick. It should encourage people to maintain hygienic practices through the use of signs, soap, disposable towels or air dryers, garbage bins next to the bathroom door, first aid kits, and a staff which sets good examples.
(ICYWW, I'll be back at the restaurant tomorrow.)
Infectious Disease in Athletes
Infectious Diseases Associated With Organized Sports and Outbreak Control
Infectious Diseases in Athletes
Infectious disease in athletes (you'll need to be registered to read the full article)
Common Sports-Related Infections: A Review on Clinical Pictures, Management and Time to Return to Sports