Droplet spread without<unk>  up to ~ for sneezes and coughs, up to ~ for talking. Aerosol spread in much further than this. Infections in general may spread by direct contact (for example, shaking hands or kissing), by inhaling infectious droplets in the air (droplet transmission), by inhaling long-lasting aerosols with tiny particles (airborne transmission), and by touching objects with infectious material on their surfaces (fomites). Different diseases spread in different ways; some spread by only some of these routes. For instance, fomite transmission of COVID-19 is thought to be rare while aerosol, droplet and contact transmission appear to be the primary transmission modes, . Coughs and sneezes can spread airborne droplets up to ~. Speaking can spread droplets up to ~. It may be difficult to maintain these distances. For a masked person, or even one sneezing or coughing into a tissue or elbow, these distances are reduced. Masking any person who may be a<unk>  of infectious droplets (or aerosols) thus reduces the unsafe range of physical distances. If a person can be infectious before they are symptomatic and diagnosed, then people who do not yet know if they are infectious may also be a<unk>  of infection. Handwashing helps to protect people against contact transmission, and against indirect droplet transmission. Handwashing removes infectious droplets that their mask caught (from either side) and which transferred to their hands when they touched their mask. For pathogens transmitted through the air, strategies to block cough air jets and to capture aerosols, e.g. the "Shield & Sink" approach, can be highly effective in minimizing exposure to respiratory secretions.
Source control 
Risk Evaluation and Mitigation Strategies
Therapeutic relationship
Cost sharing
Organ procurement
Recovery model
Theory of indispensable attributes
Guaranteed issue