of the nature of, caused by, or relating to a virus or viruses

a severe viral infection

vaccines targeted at multiple viral antigens

(of an image, video, piece of information, etc.) circulated rapidly and widely from one internet user to another

a viral ad campaign

the video went viral and was seen by millions

an image, video, piece of information, etc. that is circulated rapidly and widely on the internet

the rise of virals in online marketing