The latest two victims died in hospital intensive care units on Monday night and Tuesday morning from medical complications stemming from a wild thunderstorm that struck Melbourne on November 21, a Health Department statement said.
Another patient remained in intensive care. Another six were in hospitals with less serious respiratory and related conditions.
Last week's storm caused rain-sodden ryegrass pollen grains to explode and disperse over the city, with tiny pollen particles penetrating deep into lungs. Around a third of patients who suffered asthma attacks reported never having asthma before.
The world's first recorded thunderstorm asthma event occurred in Melbourne in 1987, when hospitals reported a five-fold increase in asthma cases. Similar events have happened in the United States, Canada, Britain and Italy. The last major event in Melbourne was in November 2010.