vampires catching human diseases

so simple human diseases such as the cold or the flu don't affect vampires. Technically, they ARE already dead, so anything that affects the lungs, the heart, the liver, the blood, almost any organ, simply have no affect (diseases need a living host, vampires are, once again, not alive). However, diseases that affect things such as the eyes, the ears, the nose, arms, legs, hands, things like that, do affect them. If it would dim any human sense, then if a vampire gets it, it affects them 10 fold. and the brain. Any mental illness or anything that would affect a normal human brain is very very dangerous for vampires. especailly becuase their brain is their most important feature.