Hospitals are stretched to their limits during unseasonably early heatwave, as medical authorities liken public health risk to a ‘natural disaster’

Medical experts in Japan are to add a “most severe” category to the current heatstroke index, amid warnings that the extreme heat is straining medical services and causing damage to public health comparable to that in a “natural disaster”.

The Japanese Association for Acute Medicine said it would add a fourth category to the three-level classification later this year in an attempt to reduce deaths from heatstroke.

The announcement came in the same week as authorities in Tokyo said six people had died from the effects of a heatwave that has sent temperatures as high as 40C in some parts of the country – well above the 35C threshold classified by weather officials as “extremely hot”.