December 1, 2016

Emergency medical services personnel in Melbourne, Australia, dealt with an unprecedented number of calls last week from people suffering respiratory symptoms as a freak weather event known as “thunderstorm asthma” swept the city. Doctors are still treating dozens of patients for a variety of serious respiratory conditions, and at least eight people have died. Meanwhile, scientists are trying to understand how this rare and little-understood event occurred.

Clouds gather over Melbourne, Australia, where recent thunderstorms have caused fatal asthma attacks. Credit: © Sunflowerey/Shutterstock

Asthma is a lung condition characterized by breathlessness, wheezing, and coughing. People with asthma suffer from inflammation of the bronchi (airways to the lungs). The inflamed airways react to irritation by swelling and constricting. These changes obstruct airflow (the ability to force air in and out of the lungs). A person may feel short of breath or have difficulty breathing. Severe attacks may involve spasms (sudden constriction) of the airways. Sufferers gasp for air and feel that they are suffocating. These attacks require immediate medical attention and can cause death.

A variety of environmental conditions, called triggers, may irritate the sensitive airways of people and cause an asthma attack. Triggers include pollen, mold spores, chemical irritants, tobacco smoke, animal dandruff, and dust mites. The term thunderstorm asthma refers to rare weather events where large storms generate powerful winds that churn up pollen and dust into the air. Recent hot, dry weather around Melbourne led to large ryegrass pollen deposits in the region. Once this pollen was in the air, thunderstorm winds ruptured the pollen grains into even smaller particles. These particles were small enough to be inhaled deep into people’s lungs, causing irritation and acute asthma attacks.

The last recorded outbreak of thunderstorm asthma in Australia was in 2010. That event was not nearly as severe as the one that occurred last week. Scientists worry that such unusual weather events will become more frequent and more deadly in Australia because of climate change.