Antibiotics are facing an existential crisis less than a century after their introduction. Increased bacterial resistance is putting the world at risk of an era in which routine infections are untreatable.

A leading killer among diseases is now targeted for eradication by the middle of this century. Efforts to combat malaria are costly and challenging.

The Zika virus, which has been found to cause severe birth defects, has spread across the Americas, prompting the World Health Organization to declare a global health emergency.