This is a Norwegian band that is why you can't understand the lyrics.
This video is about Norse Mythology and also science. Its about men eating rancid meat and getting sick. Then the oncoming plague caused by it. The owl represents the primal evolutionary force that lives in all other living things around us. We are surrounded by other life forms that will adapt to us, the fastest evolving amongst them are viruses and germs represented by the worms and serpents in the video.
It is very simple but it is an ancient warning from Norse mythology. Before these things about viruses and diseases were fully understood from science.
But ultimately I think it doesn't matter, our population was meant to be kept balanced just like any other life form and these viruses and microbes will get us eventually if something from outer space doesn't first.