Acute infectious mononucleosis (AIM), also known as mono or the ‘kissing disease,’ is caused by the Epstein-Barr Virus (EBV). In a new paper, researchers connect the onset and severity of mono to T-cells that react to both EBV and the influenza A virus, which causes the flu. The study represents one of the first reported links between how a person’s immune system responds to infection and receptors on T-cells, which instigate the immune response.