Many public health interventions were made to try to control the spread of the disease, which is mainly spread through respiratory droplets in the air, either inhaled or deposited on surfaces and subsequently transferred to a body's mucous membranes. These interventions included earlier detection of the disease; isolation of people who are infected; droplet and contact precautions; and the use of personal protective equipment (PPE), including masks and isolation gowns. A 2017 meta-analysis found that for medical professionals wearing N-95 masks could reduce the chances of getting sick up to 80% compared to no mask. A screening process was also put in place at airports to monitor air travel to and from affected countries.