This often happens to me when watching E-sport on twitch. Because on the break between match, they will use music or songs from sponsors and ads. Yeah, it feels like that. LOL
It's even worse when the song isn't in a language you know, and only a part of it gets stuck in your head. Then every so often you'll hear it in random places and it gets stuck again when you least expect it.
It feels like author was trying to demonstrate how the pandemic works in a harmless way. Manbagi was infected by the song and got to infect people around her. I know it is a BIG stretch but... Idk maybe I'm just paranoid about the pandemic.