Community associated infections remain a persistent and recognized public health risk to all. Sexually transmitted infection rates are on the rise. Tuberculosis rates are generally low but remain persistent among all communities. Hepatitis C rates are declining, but care and treatment for chronic hepatitis C infection impose a heavy burden on the health care system and there are estimates that 41 per cent of infection individuals are unaware of their infection. Diseases occur only when conditions are favorable to them to occur, in man and environment. When we are physically weak and our body resistance slides down, the mischievous microbes enter our body where they incubate and we fall ill. Same way the polluted environment around us invites the deadly germs to breed and multiply, and cause various diseases to break out. The necessary conditions for the infections or communicable diseases to occur and the processes that go with them are briefly explained in this paper.