You typically need more than just 1 virus in your system to get infected. Your immune system will do a good job of taking care of the 1. The study just says th

You typically need more than just 1 virus in your system to get infected. Your immune system will do a good job of taking care of the 1. The study just says they were able to detect live viruses after that amount of time, not that they would definitely infect you. It's likely that the odds of infection are very low before that 3 hour mark. Unless I'm misreading the study.