In 2016, on one spring day in Australia (around November), which is also thunderstorm season there, thousands of people began to have trouble breathing, all at the same time.
It was a national asthma attack that ended up killing 10 people. The culprit was something called "thunderstorm asthma" which was first identified in the 1980s.
Why does thunderstorm asthma happen?
People are just beginning to be able to answer this question. Recently, a group presented data on seven thunderstorm asthma events in Australia. In comparing the events, they found that the common factors in all of them were high pollen levels, multiple storm cells and strong winds.
A powerful thunderstorm brings with it high winds that have rising convective updrafts. These sweep pollen grains up into the sky, for miles, into areas of high humidity. The theory is that the grains then absorb moisture, swell, and as a result, rupture into hundreds of even smaller pieces. It is thought that these small pieces of pollen are more dangerous to the lungs because their size allows them to enter into the lungs and cause inflammation.
What can be done to prevent it?
Unfortunately, not much at this point. Warnings and avoidance of the area seem to be the best bet. Last October, Victoria initiated a $15.6 million dollar warning system that gives residents a warning 3 days in advance of a likely thunderstorm asthma event. The system’s advance warning should be able to give people enough time to gather asthma medications and make plans to stay indoors.
It's not just Australia, either. Thunderstorm asthma events have been reported across North America, Europe, and the Middle East. That said, Melbourne seems to have a particularly good set up for these events with lots of people, regular thunderstorms and fields of rye grass that produce lots of pollen. For more information on thunderstorm asthma, please read this document put out by The National Asthma Council Australia.