In reality, it can spread both ways. If someone sneezes or coughs respiratory droplets will be emitted into the air column. If you are in a closed environment and are close enough to someone you can breathe this in and be infected. It is also quite likely that these droplets will land on surfaces and the virus will exist there for a length of time depending upon the surface. If you touch that surface and then touch your eyes or mouth out definitely you can be infected with COVID-19. That is why all of these measures are important: social distancing, frequent hand washing with soap, and strict avoidance of touching you face (as hard as that can be). The hope for the upcoming summer months is that humid air will cause the droplets to pick up moisture and fall faster to the ground, rather than linger in cooler, dryer air. It's no secret that most viruses do much better in cooler, less humid conditions. But, even more important is that during the warm weather months more people will potentially be outdoors which reduces the likelihood of the above methods of spread. I suppose we'll know for sure in he upcoming months if the number of COVID-19 cases rises sharply in the southern hemisphere as the weather begins to cool down there.