Apart from viruses, other causes of infectious disease in humans include bacteria, fungi, parasites, rickettsias and chlamydia. Among these types of microorganisms, viruses and bacteria cause the fastest onset of disease and the most acute effects.
人類傳染病病原，除病毒外，還包括細菌、黴菌、寄生蟲、立克次體、披衣菌等，這幾種微生物中，以病毒和細菌的致病速度較快、危害較烈。