In the context of trends, graphs, statistics, does "to spike" mean numbers going sharply up and then back down, or only going up?

I always thought a spike in a graph was the shape of a spike or thorn in the physical world, with the number rising much higher than normal for a very short time, and then back to the normal line.

But in recent months it seems people refer to Coronavirus spiking when it starts to go up sharply, whether or not it's going to maintain that new level, get exponentially higher, or go back to normal.

Are these two different senses, is one wrong, is one a new emerging sense, or are they "actually just the same thing"?

While a physical spike gives the image of a quick increase and decrease, the word is often used just to refer to the increase.

M-W includes the following definition

an abrupt sharp increase (as in prices or rates)

When discussing coronavirus, a more common term has been "surge", which doesn't suggest that it's short-term.