First off, wasting and bloating represent two different problems. And then both can can have multiple different causes.
Let's focus on mycobateriosis. Here is a quote from the Introduction of a paper from 2013 on the subject which will give you an idea of what I mean:
Fish mycobacteriosis is well recognised in marine and freshwater fish, with several reviews concerning the topic (6, 7, 12). Mycobacterial infections are one of the most common infections of ornamental fish. Many mycobacterial species have been isolated from fish tissues. The following species have been detected: M. abscessus, M. aurum, M. avium complex, M. chelonae, M. chesopeaki, M. fortuitum, M. gordonae, M. haemophilum, M. insubricum, M. interjectum, M. kansasii, M. marinum, M. montefiorense, M. peregrinum, M. parafortuitum, M. poriferae, M. pseudoshottsii, M. scrofulaceum, M. shottsii, M. similae, M. stomatepiae sp. nov., M. szulgai, and M. triplex (1, 7, 13, 32).
Different strains can be more or less deadly and some can be treated while others are pretty much fatal. Moreover, it is not so easy for humans to become infected from fish and the records show that a lot of this happens in professions related to fishing and food more than in the hobby. As a rule of thumb, the most dangerous and most difficult to treat species of this disease are the ones which kill the fastest. Dead fish are a major cause of spreading but not the only way for sure.
Then there is the problem of knowing why a fish is wasting. Hexamita, a protozoan will also cause it.
The issue is trying to diagnose fish illnesses and diseases visually. We can all see ich, we cannot see most parasites, bacteria or viruses. So how does one effectively treat a symptom which can have multiple causes when we cannot know what it is for sure.
In this situation Pat Mary could be right and euthanizing the fish may be the only option. On the other hand a simple anti-protozoan treatment might solve the problem.
Kuckju- as I see it, you have a couple of options. But the most important things are not to add any new fish until things resolve themselves. Next, if you have more than one tank, you need not to share anything between them either.
Next, I would treat the tank for a protozoan issue rather than mycobacteria. You have a much better chance of beating this than if it is mycobacteria. There are a few medications that might help. One is Metrodinazole. However, this medication really needs to be fed rather than dosed into the water. if fish are not eating, it won't help. A better choice, imo, would be Flubendazole. You can read about that on the same site where I would send you to buy it. I suggest you read these two short easy to understand papers by Dr. Charles Harrison:http://www.inkmkr.com/Fish/FlubendazoleTreatment.pdfhttp://www.inkmkr.com/Fish/FlubendazoleArticle.pdf
The second paper gives the direction for how to dose Flubendazole as it is a bit difficult to dissolve in water. I use the Vodka method.
If this medication is not effective, then the odds are good that the issue is not a protozoan. At this point the next step is to try an antibiotic with the idea that perhaps it is a non-mycobacterial infection. I would suggest a broad spectrum antibiotic.
If this fails then I would fall back on Pat Mary's recommendation and euthanize all the fish and sterilize the tank and its equipment and start over.
As for how easy it is to catch mycobacteriosis from fish, it is not common. When all worldwide cases are analyzed most of them come from fish related business. The catching of food fish and their preparation for sale and aquaculture are the primary sources of cross species infection in humans. However, there have been cases of this happening in an aquarium. But the occurrence of transmission from fish to people from tanks is pretty rare.