FIVE THINGS ABOUT AN ‘ASTHMA STORM’

1 WHAT HAPPENED

A thunderstorm triggered a rash of asthma attacks across Melbourne, Australia, on Monday. The attacks claimed at least four confirmed victims: Twenty-year-old Hope Carnevali died while waiting for responders to arrive; paramedics struggled to resuscitate 35-year-old Apollo Papadopoulos, who eventually died; Omar Majoulled, 18, died two days before what would have been his high school graduation; and Clarence Leo died early Wednesday.

2 TERRIFYING IMPACT

The outbreak was severe even for those whose symptoms were mild under usual circumstances. “It felt like an elephant had his foot on my chest for about four hours,” said David McGann, who added that his asthma attacks were not normally worrisome, but during the storm they were crushing. By late Monday night, Melbourne pharmacies had depleted their stocks of bronchodilator medication.

3 WHY IT HAPPENS

During the spring, storms increase pollen’s ability to penetrate deep into the lungs. The storms concentrate pollen grains near the ground. There, the grains swell with so much water they rupture into tinier pieces, according to the prevailing hypothesis. Dispersed in the air, these particles form what is essentially a fine allergenic mist.

4 IT WASN’T A FIRST

Since the 1980s, there have been scattered reports of asthma attack outbreaks during thunderstorms, including in Naples, Italy, and Atlanta, Ga. The largest confirmed episode was in London in June 1994, when 640 Londoners visited emergency departments.

5 HOW TO SURVIVE

During the first 20 to 30 minutes of the storm, stay indoors to limit exposure to pollen. Keep windows closed with an air conditioner running to filter air. Showering will also remove particles. For those susceptible to asthma, carry a rescue inhaler.