Climate and new virus vectors; advice on prescribing opioids for pain; triggers for an oesophagal problem; cost of macular disease medication

Global warming will probably mean that wildlife travels more and mixes with other species—and an effect will be to spread unfamiliar viruses; There is new guidance to help hospital doctors and clinicians prescribing opioids for pain; A disorder of the oesophagus creates symptoms similar to reflux or allergies, but the cause of the disorder is not known; The non-availability of a treatment for age-related macular degeneration has eye surgeons arguing for change.