At least two people are believed to have died after a perfect storm triggered hundreds of thunderstorm asthma attacks and plunged Melbourne's hospitals into their busiest ever night.
Victoria ran out of ambulances last night as emergency calls jumped a staggering 450 per cent, and several hospitals enacted disaster management plans to cope with floods of patients struggling to breathe.
Health Minister Jill Hennessy said claims that two people died while waiting for ambulances during the storm would be investigated.
"No doubt, there will be lessons to learn - there always are in these cases - but every part of our emergency management surge occurred correctly," Hennessy said.
One of those who died was Hope Carnevali, Nine News reported.
The 20-year-old died on the front lawn of her home and could not be revived.
Devastated family, including an uncle spoke to Nine News.
"She was very kind-hearted, beautiful gorgeous little girl. She'd do anything for anyone," he said.
"If somebody needed her she'd be there. She was an angel. We're going to miss her so much."
It had taken an ambulance 30 minutes to arrive.
The uncle said he thought Ambulance Victoria should let people know if there were going to be delays of 20 minutes or more.
"So maybe we can take them straight to hospital where it can save a life, because I've lost my niece, maybe for that reason," he said.
The perfect storm of a high pollen count, strong northerly winds and humid conditions triggered the rare phenomenon of thunderstorm asthma from 7pm yesterday. Emergency services received calls every four to five seconds and Ambulance Victoria deployed 60 extra crews.
AV regional services general manager Mick Stephenson said he was aware that two people who had complained of respiratory-like issues had died while waiting for ambulances - including one who waited half an hour - but it was not yet known if the asthma phenomenon was responsible.
More than 1870 calls for ambulances were made between 6pm and 11pm on Monday. At least 600 callers had respiratory symptoms.
Extra staff were brought into overwhelmed hospitals, the fire brigade provided more first-responders and Victoria Police did welfare checks. Private hospitals, including Cabrini and the Epworth, opened their emergency departments for public patients.
State health commander Paul Holman said the flood of calls was a first in his 40 years in the job, calling it a "state disaster".
"Within an hour [of the storm hitting] we'd received 160 calls, and had run out of resources, " Holman said.
However, the man who discovered the phenomenon of thunderstorm asthma in 1992, Deakin University's associate professor Cenk Suphioglu, said the crisis could have been predicted.
His Deakin AIRwatch website predicted the weather combination would trigger an extreme event, but Suphioglu said more resources were needed to set up an alert system.
"If it is well resourced we can give alerts - how seriously they [emergency authorities] take those alerts will be up to them," Suphioglu said.
"This is a well-known thing. Melbourne is dubbed as not only the allergy capital of the world, but also the thunderstorm capital of the world."
Royal Melbourne Hospital ran out of Ventolin and spacers, having to borrow from neighbouring centres after seeing a day's worth of patients in 12 hours.
"There really wasn't any warning," said RMH director of emergency Professor George Braitberg. "Most people I saw weren't asthmatics or hadn't had it for 25 years. It was an extraordinary situation; the worse I've experienced in 30 years in the job."
St Vincent's Hospital had to enact its emergency management plan reserved for disasters and set up a second six-bed emergency department in its day unit when it became overwhelmed with 216 patients - more than double what sees on a typical night.
The Royal Children's Hospital (RCH) was inundated with almost 500 emergencies - two-and-a-half times the normal number of sick children. About 50 patients were admitted.
"The sheer number of patients is unprecedented in our history," RCH director of general medicine Dr Tom Connell said. "There will certainly be lessons learned about dealing with demands, but it is hard to predict these and I think we have all coped very well by pulling together in a true team spirit."
Harrowing hospital dash as son struggled to breathe
A mum has described the harrowing moment she was told to drive her son to the hospital while he struggled to breathe because there weren't enough ambulances to take him.
Stacee Krepis called 000 at 4am on November 21 after her son Nicholas, 11, had chest pains, and had struggled to breathe from about 6pm the night before.
But when the paramedic arrived to her Coburg home in a station wagon shortly after, he urged Krepis to take Nicholas straight to the Royal Children's Hospital.
"I rang the ambulance, but a paramedic came on his own, and when he saw Nicholas, he said yes, I needed to take him to the Royal Children's straight away," Krepis said.
But after a dash to the hospital, Krepis was confronted with dozens of children in the waiting room, coughing and wheezing.
"Some of those kids in there were really struggling. It was scary, especially seeing your child unable to breathe," Krepis said.
Krepis said when she finally got to see a doctor, he told her the "line was out the door with children with similar symptoms" by midnight.
Perfect storm a rare event
"Thunderstorm asthma" is a rare spring event that happens when a thunderstorm, sudden change in humidity, a northerly wind change and high pollen count are combined.
This perfect storm causes pollen "packages" to be blown from the north.
The humidity change bursts the capsules, which explode tiny pollens at concentrations a million times higher than what is usually in the air and irritate airways.
People with mild asthma, or who have never experienced an asthma attack, are often most affected because they aren't actively taking treatment or have management plans.
Melbourne is the "thunderstorm" capital of the world. Epidemics were recorded in 1987, 1989 and November 2010.
Royal Melbourne Hospital's head of respiratory medicine, associate professor Lou Irving said the event was a reminder to mild asthmatics that their condition could suddenly become severe and they needed an action plan and current medication.