Nat. Med. 16, 374–376 (2010); published online 7 April 2010; corrected after print 6 May 2010

In the version of this News and Views initially published, the last name of one of the authors whose work was being discussed, Jonathon N. Winnay, was incorrectly spelled as 'Winney'. The error has been corrected in the HTML and PDF versions of the article.