Agents that can be transmitted by the aerosol route have caused most laboratory infections. It is wise, when planning work with a relatively uncharacterized agent with an uncertain mode of transmission, to consider the potential for aerosol transmission . The greater the aerosol potential, the higher the risk. Factors such as desiccation, exposure to sunlight or ultraviolet light, or exposure to chemical disinfectants must be considered. The infectious dose of the agent is another factor to consider.
Infectious dose can vary from one to hundreds of thousands of units.
The complex nature of the interaction of microorganisms and the host presents a significant challenge even to the healthiest immunized laboratory worker, and may pose a serious risk to those with lesser resistance. The volume of concentrated material being handled is also important. In most instances, the risk factors increase as the working volume of high-titered microorganisms increases, since additional handling of the materials is often required. The origin of the potentially infectious material is also critical in doing a risk assessment. From another perspective, this factor can also consider the potential of agents to endanger American livestock and poultry.