Direct transmission also involves droplet contact, where sneezing, coughing or talking contaminates the air with droplets. Cold and flu viruses are most commonly spread by droplet contact. Even with droplet contact, the contact must be direct, since droplets generally do not travel more than 12 feet from the source. Indirect transmission occurs when an infected person spreads the infection to an inanimate object, and a noninfected person touches or otherwise comes into contact with the infected object. Equipment and instruments often spread disease as can soil, air, insects, food, milk and water.
Airborne transmission is much like droplet contact but it is more diffused.
Droplets that are sneezed, coughed or otherwise sprayed into the air evaporate but the residue remains in the air for long periods of time. Airborne dust particles pick up some of these bacteria or other disease causing organisms and air currents help to spread them over a wide area. The disease-causing organisms then are inhaled by or come to rest on a susceptible person who is subsequently infected. A person may drink contaminated water or may eat contaminated food or it also could occur as a result of the injection of contaminated blood or contaminated drugs. Vector transmission occurs when an animal provides the route of transmission to a person such as an infected tick causing Rocky Mountain spotted fever or an infected mosquito transmitting malaria.