Whooping cough, also known as pertussis, is a highly contagious bacterial infection of the respiratory system. It is characterized by severe coughing fits that can last for weeks or months and can be accompanied by a 'WHOOP' sound when the person breathes in. It is most common in infants and young children, but can affect people of any age. Vaccination is the best way to prevent whooping cough, but it is still important to be aware of the symptoms and seek medical attention if they occur.