No one can fail to have been moved by the utter devastation this week in the Philippines. Flattened cities, parents cradling the bodies of their children, survivors’ reports of loved ones washed away from their grasp – our natural human response is empathy. The people who survive devastating events such as Typhoon Haiyan need assistance. Relief agencies that provide it deserve public support.

It is an imperative to offer shelter, nutrition, sanitation and medical care to those suddenly bereft of it; without aid, humanitarian crises would cause still greater suffering. Yet admiration for the agencies that deliver relief should not blind us to the need to ensure that it is well delivered. Humanitarian responses must be founded on good evidence.

The evidence base, unfortunately, is weak. We know that storms, earthquakes and conflicts have devastating consequences for health and wellbeing, and that not responding is not an option, but we know surprisingly little about how best to go about it. Not only is evidence-based practice rare in humanitarian relief operations, it is often impossible.