| The pattern of Transmission route (PTR) | Particles involved and particle characteristics | Characteristics/definition of transmission | References |
| Contact | Self-inoculation of mucous membranes by contaminated hands. | [21] | |
| Direct | Deposited on persons. | Virus transfer from one infected person to another. | [22] |
| Indirect | Deposited on objects. | Virus transfer through contaminated intermediate objects (fomites). | [23] |
| Airborne Droplets | Droplets (>5 µm) | Short-range transmission. | [20] |
|
| Remain only shortly in the air (<17 min) | Direct inoculation of naïve person through coughing/sneezing/breathing of an infected person. | |
| Dispersed over short distances (<1 m) | Deposition mainly on mucous membranes and upper respiratory tract. | ||
| Aerosol Droplets | Aerosols, droplet nuclei (>5 µm) | Long-range transmission (LRT) | [24] |
| Remain in the air for an almost infinite amount of time | Inhalation of aerosols in a repairable size range (RSR) | ||
| Dispersed over long distances (>1 m) | Deposition along the respiratory tract, including the lower airways. |