Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Horizontal transmission is the transfer of infectious agents between individuals of the same generation. This can occur through direct contact, respiratory droplets, or vectors like insects.
5 Must Know Facts For Your Next Test
Horizontal transmission is distinct from vertical transmission, which occurs from parent to offspring.
Common examples include the spread of viruses like influenza and HIV.
Vectors such as mosquitoes can facilitate horizontal transmission of viruses like Zika and Dengue.
Horizontal transmission can occur rapidly in crowded environments due to close proximity and frequent interactions.
Preventative measures include vaccination, hand hygiene, and vector control.
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Related terms
Vertical Transmission: The passing of an infectious agent from parent to offspring, often during childbirth or breastfeeding
Vector: An organism that transmits pathogens from one host to another, such as mosquitoes or ticks
Direct Contact Transmission: Spread of pathogens through physical contact with an infected individual