Can a Curse be real? Perhaps that depends upon who you ask.
http://www.coasttocoastam.com/show/2014/10/10
http://listverse.com/2007/10/11/top-10-bizarre-curses ,
http://www.themystica.com/mystica/articles/c/curses.html ,
Sometimes a curse is just based on an urban legend or prank.
http://www.cracked.com/article_18809_the-6-most-strangely-convincing-real-life-curses.html
However, there are times where there is still no adequate explanation in conventional terms.
