Whooping cough produces a distinctive high-pitched “whoop” sound when the person gasps for air after a violent burst of coughing. The whoop happens on the inhale, not the exhale, which is what sets it apart from almost every other type of cough. It sounds something like a sharp, strained intake of breath forced through a narrowed airway, and it can be alarming to hear, especially from a child.
The Sound Itself
A whooping cough episode doesn’t start with the whoop. It starts with a rapid-fire series of forceful coughs, one right after the other, with no chance to breathe in between. These coughs come in clusters called paroxysms, and they can be so intense that the person’s face turns red or even slightly blue from lack of oxygen. At the end of this burst, when the lungs are nearly empty, the person finally inhales hard. That desperate inhalation through swollen, narrowed airways creates the high-pitched whooping noise.
The whoop itself lasts about a second, but it’s unmistakable once you’ve heard it. Some people describe it as a crowing or gasping sound, almost like the noise a person makes when choking and then suddenly getting air. After the whoop, there’s often a brief pause before the next round of coughing starts. Many people vomit immediately after a coughing fit because of the sheer force involved.
Why It Sounds Different From Other Coughs
Whooping cough is sometimes confused with croup, but the two sound quite different. Croup produces a harsh, barking cough that sounds like a seal. That bark happens when the person coughs out. With whooping cough, the cough itself may not sound particularly unusual. It’s the inhale afterward that’s distinctive. If the alarming sound comes at the end of a coughing fit rather than during the cough, that pattern points more toward pertussis.
A regular chest cold or bronchitis can cause prolonged coughing, but those coughs typically allow the person to breathe between each one. Whooping cough paroxysms are relentless, stacking cough after cough with no air break, which is why the inhale at the end is so forceful and noisy.
Why the Whoop Happens
The bacteria that cause whooping cough trigger a chain reaction in the airways. The infection produces toxins that stimulate nerve endings in the respiratory tract, essentially making the cough reflex hypersensitive. These toxins cause the body to produce a compound called bradykinin, which activates pain and irritation receptors on the nerves lining the airways. The result is an exaggerated, uncontrollable cough reflex that fires repeatedly.
At the same time, the airways become inflamed and swollen, which physically narrows the space air has to pass through. When the person finally inhales after a coughing paroxysm, air rushes through that tight opening and vibrates the surrounding tissue. That vibration is what produces the whoop. It’s the same basic principle as the sound you hear when you blow across the mouth of a narrow bottle, just happening in reverse as air rushes in.
Babies Often Don’t Whoop at All
This is the most important thing parents should know: many babies with whooping cough never make the classic whooping sound. Infants under a year old, and especially those under six months, may not cough much at all. Instead, they may have apnea, which means their breathing temporarily stops. During these pauses, a baby may turn blue or purple around the lips and face, a sign called cyanosis.
In babies, the thing to watch for isn’t a sound but a silence. If an infant is struggling to breathe, gagging, or having visible pauses in breathing, those signs can indicate whooping cough even without the signature whoop. This is part of why pertussis is most dangerous in the youngest children: the classic warning sound that prompts parents to seek help simply doesn’t occur.
How the Cough Develops Over Time
Whooping cough doesn’t start with the whoop. The first week or two looks and sounds exactly like a common cold: runny nose, mild cough, maybe a low fever. During this early stage, called the catarrhal phase, there’s nothing about the cough that would make you think it’s anything serious. This is also, unfortunately, when the person is most contagious.
After one to two weeks, the cough shifts. The mild cough transforms into intense paroxysms, and the whoop begins to appear. This is the paroxysmal stage, and it can last anywhere from one to six weeks, sometimes longer. Coughing fits tend to be worse at night and can be triggered by eating, laughing, or physical activity. Between episodes, the person may seem perfectly fine, which can be confusing. Someone might have a dozen severe coughing fits in a day but appear completely normal in between them.
Eventually the fits become less frequent and less intense during the recovery phase, but a lingering cough can persist for weeks or even months. In China, whooping cough is sometimes called the “hundred-day cough” for this reason.
What Clinicians Listen For
A cough illness lasting two weeks or more raises suspicion for whooping cough if it includes any of these features: paroxysms of coughing, an inspiratory whoop, vomiting right after coughing, or apnea. You don’t need all four. Even one, combined with a cough that won’t quit, is enough to warrant testing. Adults and vaccinated individuals sometimes have a milder version where the whoop is faint or absent, making the diagnosis easy to miss. If you’ve had a persistent cough for more than two weeks that comes in uncontrollable bursts, especially if it worsens at night, it’s worth mentioning pertussis as a possibility to your doctor even if you don’t hear a clear whoop.