More than 3,500 people are infected , and more than 1,900 have died , WHO says . Comment: A nurse from the UK who had been infected leaves the hospital .
More than 3,500 people are infected , and more than 1,900 have died , WHO says . International response to `` global crisis '' inadequate , Medecins Sans Frontieres says . A nurse from the UK who had been infected leaves the hospital .