A health worker cleans his hands with chlorinated water before entering an Ebola screening tent at the Kenema Government Hospital in Sierra Leone. More than 300 Sierra Leoneans have died of the disease. Michael Duff/AP hide caption

itoggle caption Michael Duff/AP

A high-resolution image of the molecular carrier that moves the botulinum toxin from the intestine into the bloodstream. The carrier (silver) creates gaps in the gut lining by grabbing the rope-like molecules (red ribbons) that tether one intestinal cell to the next. Rongsheng Jin, UC Irvine, and Min Dong, Harvard Medical School hide caption

itoggle caption Rongsheng Jin, UC Irvine, and Min Dong, Harvard Medical School