Whooping cough is caused by Bordetella pertussis, a type of bacteria. It’s passed on through close personal contact, sneezing and coughing.
The bacterium infects the lining of the airways, mainly the windpipe (trachea) and the two airways that branch off from it to the lungs (the bronchi).
When the Bordetella pertussis bacterium comes into contact with the lining of these airways, it multiplies and causes a build-up of thick mucus. It's the mucus that causes the intense bouts of coughing as your body tries to expel it.
The bacterium also causes the airways to swell up, making them narrower than usual. As a result, breathing is made difficult, which causes the 'whoop' sound as you gasp for breath after a bout of coughing.
Whooping cough diagnosis
See your doctor as soon as possible if you think you or your child may have whooping cough.
Your doctor may suspect whooping cough by asking about your or your child’s symptoms. They will confirm the diagnosis by taking a swab from the back of the nose or throat.
Some people may need a chest X-ray to see if they also have developed pneumonia.
If a young baby has suspected whooping cough they need to be tested for it straight away, and if concerned your doctor may refer them to hospital. This is because the disease can be severe in babies.
Last reviewed: May 2017