The disease called Chlamydia bacteria is caused by both bacteria and virus and it mainly acts as a host causing much harm to the main organism. This condition is quite apparent in humans as they need the ATP the energy molecule to reproduce in large numbers and this molecule is mainly found in human beings. This is the reason you can trace this molecule only in humans. In short human body is the host of this bacterial type. The Chlamydia bacteria can well travel from one body to another and this is the reason why this disease can spread so fast. This makes it clear that the disease can cause immense contamination and infection.