An infectious or communicable disease is an illness caused by the transmission of a specific microbial agent (or its toxic product) to a susceptible host. The agents can be bacteria, viruses or parasites. The majority of microbes are harmless to humans. Some, although not universally pathogenic, are potentially dangerous and my cause disease in unusual circumstances. Caution is needed not to attribute a disease to an organism which happens to be present as a commensal or contaminant. continue reading…







