Explain what is meant by “raising the line”

"Raising the line" is, essentially increasing the healthcare system capacity.

Explanation:

In the context of the Coronavirus, by "raising the line", we are trying to increase the amount of hospital beds, personal protective equipment for healthcare professionals, ventilators, and other supplies. In places like Italy, the cases have already surpassed the "line", and thus they have seen cases above the capacity and capabilities of many hospitals, causing healthcare professionals to be forced to choose who to treat.