Is there only one disease? Is it a misconception that there are many diseases?

There is only one human disease,and there are not thousands of different diseases. Now, its obvious that many of you will come up with HIV and influenza as two different diseases,but the truth is HIV virus has never been seen till present. It's just an assumption of virus or a hypothesis. Most diseases are tested using a symptom based formula for determining which disease you have. Viral loading is used for HIV. This viral loading is determined in a simple way. Well,first,a blood sample is taken and put in a blender,and at last,the result is filtered. Then the particles of a certain size are said to be 'viruses'. Just because a particle of matter is of a certain size,it doesn't make it a virus.
It is well known that if we avoid some chocolates or anything else,we will never get a 'cold','flu' or 'influenza virus.' Well that's because there are no viruses.
The bacteria in the gut can leak into the blood stream by a problem called leaky gut syndrome which is caused by an inappropriate diet. This is the cause of a disease. Therefore,there is only one disease which is a vitamin deficiency disease.
How do viruses organise themselves to attack humans when they have no senses of any description? Well first of all how did the first person discover virus without a reference photo of what it looks like? This proves that viruses couldn't be found even if they exist. An electron microscope will not be able to locate something as small as a virus. If you see any photos of viruses,they are usually digital creations of what people think a virus looks like. So now what do you think about existence of various diseases?