Invasion of space isn't just getting too close to somebody, it also involves your senses such as smell, sight, hearing, touch and taste. For example if you smell a unpleasant smell from somebody who just farted that is invading your personal space.  

The picture above shows us the girls personal space although something we break this 'invisable force field' by letting people close to us such as our boyfriend, family and friends.

Viruses are also a one of many things that invade our personal space. They come into our body without any control from us and take over killing things in its way.

Viruses are the most harmful of these "space invaders".