Dispersion characteristics of respiratory droplets are important in controlling transmission of airborne diseases indoors. This study investigated the spatial concentration distribution and temporal evolution of exhaled and sneezed/coughed droplets in a ventilated hospital ward. The viability function of airborne bacteria was experimentally determined and encorporated into an air infection model with calculated results to estimate exposures and infection probability to the bacteria. The diffusion, gravitational settling and deposition mechanism of particulate matter were accounted by using an Eulerian modeling approach. The simulation results indicated that the ventilation flow was found to play a significant role in aerosol transport, leading to different spatial distribution patterns in infection droplet. The smaller size of infection droplet caused higher chance of ventilation from the outlet. The possibility of the proposed exposure estimation into the dose–response model for infection risk assessment was discussed. The infection probability is broadly different from 10^-6 to 7.2% by receptor's position and location and size of infection droplet conditions.