Thunderstorm asthma: Death toll in Melbourne rises to six

Updated: 

Six people have died and five remain on life support after a rare condition known as thunderstorm asthma struck Australia's second largest city.

The sixth victim died in hospital on Saturday night from medical complications, after a wild thunderstorm hit Melbourne on Monday night, the health department said.

Around a third of patients who suffered asthma attacks on Monday reported never having had asthma before.

Five patients remain in intensive care units, with three of them in a critical condition, according to the health department.

Another 12 people were in hospitals with less serious respiratory and related conditions.

Thunderstorm asthma occurs when rain-sodden ryegrass pollen grains explode and disperse over the city. Tiny pollen particles then penetrate deep into people's lungs.

views across Melbourne
The last major thunderstorm asthma event in Melbourne was in 2010 (David Davies/PA)

Emergency services and hospitals in Melbourne, which has a population of 4.5 million people, were overwhelmed following Monday's storm. Some 8,500 people needed to receive hospital treatment.

The world's first recorded thunderstorm asthma event occurred in Melbourne in 1987. Hospitals reported a five-fold increase in asthma cases at the time.

The United States, Canada, Britain and Italy have all been hit by similar events in the past. The last major time it happened in Melbourne was back in November 2010.