What does 严防境外输入 mean? What does this mean? 严防境外输入

Seems it is common in social media at the moment. 

Does it mean "avoid foreign influence" or "avoid foreigners immigrating or visiting"?
It should be interpreted in the context of the current coronavirus situation, and it means to take precautions [against the virus, or people infected with the virus,] from coming from outside the border (and infecting more people inside the border).