Pertussis (whooping cough)

What it is

Pertussis is a highly contagious respiratory infection caused by Bordetella pertussis. It is known as the cough of 100 days.

How it presents

It runs in phases:

• Coryzal symptoms first.
• Then paroxysmal whooping cough with inspiratory whooping, worse at night.
• Apnoea. If you suspect BRUE, you must rule out pertussis.
• The paroxysmal cough and the apnea are followed by vomiting - post tussive vomiting.

That last one is also how pertussis is seen from the other side: among the red flags for vomiting, vomiting post paroxysmal cough is pertussis, in the same list as bile-stained vomiting for intestinal obstruction and projectile vomiting for pyloric stenosis.

How it is diagnosed

Work up: nasopharyngeal culture, PCR swab, and serology. On the blood count, CBC shows lymphocytosis.