1. Background

1.1 How laboratory infections occur

In order to know how to avoid laboratory infections, one must understand the ways in which they occur. Infections in the laboratory, as in nature, are caused by the invasion of an infectious agent into the body via one of four routes:

1. Through the respiratory tract, by inhalation of droplets or by dry particles as an aerosol, carrying infectious agents.
2. Through the intestinal tract, by swallowing infectious liquids or solids.
   Because of the proximity of the aesophagus to the trachea, infectious material that was inhaled through the nose can reach the aesophagus and vice versa.
3. Through the skin, by pricking or cutting by a sharp contaminated object; by a bite of an animal or insect carrying the infectious agent; or by contamination of bruised skin or mucous membrane by infectious materials .
4. Ocular or conjuctival exposure.

After the infection invades the body, developing an illness depends on several factors, among which are:

• the characteristic of the agent
• the quantity that penetrated
• the immunological state of the person
• the treatment he or she receives