The weekend of May 17, writer Lindsay Kujawa and her toddler son Ronin were at a family pool party. Kujawa sat at the edge of the pool while Ronin played on the top step of the spa, and for five seconds she shifted her position to say something to a relative. Suddenly, she noticed Ronin wasn’t on the step and was instead being whirled around by the jets in the whirlpool, frantically trying to get his head above water. She pulled him out immediately and other than him coughing and being very upset, he seemed totally fine after a few minutes and they went on with the rest of the party.

When they got home later on that day, Kujawa noticed that Ronin was acting a little odd—he seemed extremely tired and had a weird cough. To be on the safe side, she put a call into his pediatrician, and was surprised to get an immediate call back. The usually calm pediatrician was emphatic that they go to the ER immediately, because she thought Ronin may have been experiencing secondary drowning.

At this point, Ronin was almost unresponsive.

Many parents have never heard of secondary drowning, but it can happen in a pool, in the ocean, and even in a bathtub. “It occurs when a small amount of inhaled fluid acts as an irritant, causing inflammation and leakage of liquid into the lung,” says Michael Roizen, MD, chief wellness officer at the Cleveland Clinic and co-founder of YouBeauty. “In some cases, the body may respond by pushing even more liquid into the lungs (this is called pulmonary edema) over the following hours, reducing the ability to breathe and leading a person to drown in their own body fluids.” The reaction can take place up to 72 hours after a near drowning incident.

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Luckily for Kujawa and Ronin, the ER doctor saw them right away and quickly ordered a round of blood tests and X-rays. His chest X-rays were not good: The doctor said his lungs were aspirated, which could be very serious, and he immediately ordered an ambulance to transport them to Children’s Hospital in San Diego to see a pediatric specialist.

Ronin turned out to be OK—the water in his lungs began to clear out after treatment and close monitoring. One doctor told Kujawa that this freak accident happens more often than you’d think—there were two other cases on the same floor with secondary drowning symptoms that very day! She also said it was right to bring Ronin in and that many times it goes terribly wrong for children in similar situations (as in, their parents put their kids down to sleep and they never wake up again.)

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We’d never heard of secondary drowning until reading Lindsay’s story—and we just had to pass it on to our readers. It turns out that the World Health Organization has tried to limit use of the term “secondary drowning” since it issued a 2005 report aimed at improving reporting and prevention around the world. The paper called for secondary drowning (along with five other types) to all be considered the same thing—drowning—whether or not the incidents are fatal or the effects immediate.

Regardless of what you call it, as we can learn from Ronin, it’s still very much a threat to small children. “If your child breathes in water or comes out of the pool coughing or sputtering, monitor them closely, keeping an eye out for difficulties in breathing, extreme tiredness or behavioral changes,” says Roizen. “All of these are signs that your little swimmer may have inhaled too much fluid.”

Secondary drowning is something every parent needs to know about, so please read this if you’re a parent or share it if you’re a friend of a parent!

Learn more about Lindsay’s experience at her blog, Delighted Mama.