I think you are incorrect to claim that the world is "becoming unhealthy." In fact, many diseases that were once a huge threat to humans are either eradicated or controlled. Here's a list of diseases that have been controlled or eradicated and how many lives are saved annually: http://www.unicef.org/pon96/hevaccin.htm
Viruses, bacteria, and other disease-causing organisms have coexisted with humans since the dawn of mankind. They have evolved along with humans and are still evolving. Fortunately in recent times our scientific understanding has grown immensely and humans have been able to either grow immune to certain diseases and/or control/eliminate them.
Will there come a day when all disease is eradicated? Who knows? In the mean time, don't let the news networks scare you. Their job is to inflate the facts to sell more of their publication. If you want to know about the current state of disease in the world, it would be better to look into actual research organizations and actual numbers.