Gunnera is a family of herbaceous flowering plants (http://en.wikipedia.org/wiki/Gunnera).
I will assume what you are referring to is Gonorrhea, a rather nasty Sexual Transmitted Infection (STI). It is 'caught' by having unprotected sex with an infected person. However, some people don't know that they have it until later - symptoms can take between two and thirty days to appear.
Check out Wikipedia for more information.
http://en.wikipedia.org/wiki/Gonorrhea