Disease Transmission Health Article

Definition

Disease transmission is the means by which contagious, pathogenic microorganisms are spread from one person to another.

Description

There are four major pathways by which pathogenic organisms may be spread to an individual: contact transmission, airborne transmission, vehicle transmission, and vector transmission.

Contact transmission

Infectious particles may be spread through direct or indirect contact with an infected individual, animal, or inanimate object. Direct contact refers to instances in which there is direct person-to-person spread of a disease. This occurs in the case of sexually transmitted diseases (STDs), when the genitals of one individual come into direct contact with the genitals of a person suffering from an STD such as herpes simplex virus (HSV). Contact of an uninfected person with infected wounds or blood may result in direct transmission, such as in the case of human immunodeficiency virus (HIV), if he/she is not protected by universal precautions.

A very common form of direct contact transmission occurs when infectious particles in the form of airborne droplets are expelled by an infected individual by sneezing or coughing and inhaled by another individual. Expelled droplets may travel for several meters before falling and therefore are easily spread to surrounding individuals. Examples of diseases that are caused by inhalation of infectious droplets are influenza (caused by the influenza virus) and tuberculosis (caused by the bacterium Mycobacterium tuberculosis).

Indirect contact results in the transmission of infectious particles from person to person via an intermediary carrier. Inanimate objects such as eating utensils, medical instruments, or equipment used in food preparation may become contaminated with a pathogenic microorganism and in turn spread the disease to other individuals. Infected needles may be the source of indirect transmission of pathogens between intravenous drug users. The hands of a health care worker may also cause the transmission of infectious particles from patient to patient if adequate handwashing practices are not enforced.

Organ transplantation presents a unique mode by which disease may be transmitted. Microorganisms that have disseminated to the donor organ may be transplanted to the recipient and subsequently cause disease. For example, hepatitis C virus (HCV) may be transmitted by liver transplantation if the donor organ is infected. Similarly, transmission of cytomegalovirus (CMV) from infected donor kidneys may occur.