Transmission (medicine)

Transmission (medicine)

In medicine and biology, transmission is the passing of a communicable disease from an infected host individual or group to a conspecific individual or group, regardless of whether the other individual was previously infected. Sometimes transmission can specifically mean infection of a previously uninfected host.

The term usually refers to the transmission of microorganisms directly from one person to another by one or more of the following means:

• droplet contact – coughing or sneezing on another person
• direct physical contact – touching an infected person, including sexual contact
• indirect physical contact – usually by touching soil contamination or a contaminated surface
• airborne transmission – if the microorganism can remain in the air for long periods
• fecal-oral transmission – usually from contaminated food or water sources

Transmission can also be indirect, via another organism, either a vector (e.g. a mosquito) or an intermediate host (e.g. tapeworm in pigs can be transmitted to humans who ingest improperly cooked pork). Indirect transmission could involve zoonoses or, more typically, larger pathogens like macroparasites with more complex life cycles.