Two people have died in Melbourne, Australia, from “thunderstorm asthma,” a rare phenomenon which occurred following a storm that struck the city on November 21. 
The 2 fatalities included an 18-year-old girl who was just days away from her high school graduation, and a female law student who died on her front lawn while waiting for an ambulance to arrive.
Thousands of people phoned for help with breathing problems, stretching hospitals and paramedics to their limits. One senior health official described the event as a “state disaster.”
The whole thing could have been predicted by authorities, according to associate professor Cenk Suphioglu, an environmental allergist from Deakin University, who first coined the phrase “thunderstorm asthma.” Suphioglu said the outbreak was caused by a “perfect storm” of asthma-triggering conditions. He explained:
“We’ve had a lot of rain, which means there’s a lot of grass, which means there’s a lot of pollen.”
It is currently springtime in Australia.
Suphioglu said the rain broke up the pollen, releasing an abnormally high concentration of microscopic particles into the wind, which easily made it into the airways and lungs of the people affected. Conditions were so extreme that even people who had never been affected before experienced difficulty breathing.
Monday’s rye grass particle count was more than double what would be considered high on a normal day. 
Professor George Braitberg, director of emergency services at Royal Melbourne Hospital, said:
“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.” 
Approximately 1,900 calls were made to ambulance services during a 5-hour period, sometimes coming in every few seconds. The situation prompted many hospitals to enact their disaster management plans.
At Royal Children’s Hospital, nearly 500 children were brought in, and scores were admitted.
As of November 22, dozens remained in intensive care, and more deaths were expected.
Suphioglu said resources were needed to set up an alert system that would hopefully prevent a similar tragedy in the future.
“Thunderstorm asthma” is so rare that it has only occurred twice in Melbourne in this century. 
 BBC News