The most common virus is the common cold, which is actually caused by several different families of viruses. Even though you may experience upper-respiratory symptoms associated with a bacterial infection, most cases of the common cold are not caused by bacteria-which make antibiotics useless against them.
Colon infection is caused when harmful bacteria resides in the colon. Normally, human immune system kills the harmful bacteria but there are some strains of bacteria that grow uninterruptedly even with strong immune system. When such bacteria overgrow in the large intestine, they can cause lot of complication.
1 Family history â If members of your family have had colon cancer, there's a greater chance that you may get it.  Poor diet and physical inactivity â If your diet is high in fat, it can increase your risk for colon cancer. Also people who are not active have a higher risk.