Sixth person dies in Melbourne 'thunderstorm asthma' outbreak

A sixth person has died almost a week after Melbourne was hit by an unprecedented "thunderstorm asthma" outbreak.

The patient, who had been in a critical condition, died in hospital on Saturday night as a result of what's been dubbed thunderstorm asthma causing other "medical complications", a hospital spokeswoman said.

"There have now been six deaths that may have occurred as a result of conditions relating to the thunderstorm asthma events on Monday," the health department said in a statement on Sunday.

Melbourne's "thunderstorm asthma" has now claimed six lives. Source: 7 News

Authorities declined to reveal any personal details about the latest victim.

However, it is understood the death occurred in the intensive care unit at one of the hospitals in the Eastern Health network.

Hope Carnevali, Omar Moujalled, Apollo Papdopoulos and Clarence Leo all lost their lives to "thunderstorm asthma.

A fifth person died in hospital on Friday.

Five patients remain in intensive care in Melbourne hospitals. Three are in a critical condition.

A further 12 are in hospital battling a variety of respiratory and related conditions.

Monday's asthma storm overwhelmed emergency services and hospitals.

Hope Carnevali, Omar Moujalled, Apollo Papdopoulos and Clarence Leo all lost their lives to "thunderstorm asthma". Source: 7 News

Included among the previously confirmed asthma deaths include Noble Park father-of-two Clarence Leo, 35-year-old Apollo Papadopoulos, law student Hope Carnevali, 20, and Year 12 student Omar Moujalled.

Paramedics dealt with an unprecedented 1,900 emergency calls in five hours on Monday evening as the phenomenon swept the state.

Melbourne hospitals across Monday and Tuesday treated more than 8,500 patients.

The government has launched a review into how emergency and health services can better respond to and manage such rare events.

The phenomena occurs when rye grass pollen gets wet, breaks into smaller pieces and enters people's lungs, causing them breathing issues.

It is only known to have occurred in Australia several times before.