A large part of fighting disease is social. If people feel cut off, isolated, abandoned, etc or if their economy is impacted more than necessary, it can lead to unrest, making it more difficult to fight the disease on the ground. It also makes people more likely to hide and/or try to escape through alternate routes. It's easier to lose track of people that way. Overall, I think it's very possible that a strict ban could make us less safe in the long run in exchange for a feeling of temporary safety.
To those who are in favor of the travel ban, why do you think one has not been put in place already?