When heat waves become killers

Once the core temperature gets above 40C, you're in serious trouble. High internal temperatures lead to increased pressure in your skull and decreased blood flow to the brain. Not a good combination.

Very high internal temperatures, for example 49C, can directly destroy the cells in your body. At this stage you're dying and quickly.

Chicago

We know a lot about the social effects of heat waves because they have been studied intensely and none more so than the great Chicago heat wave of 1995 which killed more than 500 people.

On July 16, 2005 Chicago felt tropical. The temperature hit 41C. For a week the heat ran between the low and high 30's. The night temperatures didn't provide any relief. Chicago's houses and apartments baked.

The city set new record for power use. At one point 49,000 Chicagoans had no power. Just like the 200,000 Melbournians and Adelaidians who suffered power failures during the heat wave.

By Friday evening on July 18, thousands of Chicagoans had developed severe heat related illnesses. Paramedics couldn't keep up with the emergency calls and city hospitals were inundated. The most over crowded place in the city was the Cook County Medical Examiners Office where police transported hundreds of bodies for autopsies.

By Saturday - just three days in to the heat wave - the morgue was full and a fleet of refrigerated trucks were used to store the bodies.

During the peak of the heat wave from January 28 to February 6, the South Australia Government had to create a temporary morgue, as the main morgue at the Forensic Science Office was full with 72 bodies.

They bought in refrigerated trucks. From January 28 to January 30 the Melbourne morgue dealt with more than twice as many bodies as in the same time last year.

The state coroner Judge Jennifer Coate said they were being kept elsewhere. "We'd made arrangements for appropriate facilities around Melbourne - that includes hospitals and funeral directors largely," she said.

Ambulance Victoria operations manager Paul Holman said the service went in to major disaster mode as it struggled to respond to 1,600 jobs a day - double the normal number.

The US Centre for Disease Control and Prevention did a thorough study of individual-level risk factors for heat wave victims and they came up with a list of conditions of vulnerability: living alone, not leaving home daily; lacking access to transportation; being sick or bedridden; not having social contacts nearby, and not having an air conditioner.