Droplet

When we breathe, cough, and sneeze, tiny droplets are released into the air. These droplets can carry a pathogen suspended in the liquid. Depending on the size of the droplets and the mass of the pathogen, the droplets can fall quickly to the ground or could travel a greater distance from the host. Droplets spread infection by being absorbed through mucous membranes in the mouth, nose, eyes, and throat.

Examples: COVID-19, Common Cold, Influenza.

Blood or fluid borne

Similar to droplets, blood and fluid borne pathogens transfer from the body in blood, saliva, semen, and other fluids. However, infection is caused by that fluid coming in contact with either an opening in the skin like a cut, or the mucous membranes of the mouth, nose, and eyes.

Examples: HIV, Hepatitis B & C.

Airborne

Pathogens that leave the body through droplets that are so small and light that they do not immediately fall to the ground are considered airborne. These droplets are light enough to be carried on air currents and can travel far from the host to infect another person.

Examples: Measles, Chickenpox, Tuberculosis.

Vector-borne

A vector-borne disease is transmitted by other organisms, such as mosquitoes and ticks. The vector will draw blood from an infected host and then later bite an uninfected person, which can transfer the disease to them. Contaminated needles are another example of a vector for transmitting disease.

Examples: Zika virus, Lyme disease, Rabies, West Nile Virus

Fecal-Oral

This is the transmission of disease through contaminated food, water, or hands. A pathogen leaves a host in fecal matter and due to cross-contamination, it will enter a new host usually through the mouth. Poor hand-hygiene is the most common method leading to food poisoning or other infections. Contaminated water or food supplies when waste processing is too close to a water source is a common issue in less-developed areas.

Examples: Hepatitis A, Salmonella, Cholera, Rotavirus