What is pertussis?

Pertussis, commonly known as whooping cough, is a respiratory infection that is very contagious. It usually results in prolonged and repeated bouts (paroxysms) of coughing in children and adults. These coughing episodes can continue for weeks or even months after the onset of the illness. Prolonged coughing causes air to be expelled from the lungs. When the person gasps for air after a coughing fit, a loud, high-pitched “whooping” noise might accompany the inhalation of air. That is the reason pertussis is called whooping cough. However, someone may still have whooping cough without making a whooping noise.

Instead of coughing spells, babies who are infected with pertussis may experience breathing difficulties, such as a pause in breathing (apnea). About 50% of babies less than one year old who get whooping cough have to be hospitalized. In rare cases, death may occur.

How common is pertussis?

Pertussis is a common disease. Throughout the world, there are about 16 million cases of pertussis each year, resulting in about 195,000 deaths. In the United States, over 48,000 cases of pertussis were reported in 2012. However, many more cases occurred that were not reported. The number of reported cases of whooping cough has been increasing since the 1980s.

People of all ages can get pertussis, but it occurs most often in children and adolescents. Even adults and children who have been vaccinated against it can become infected, although their symptoms are usually milder.

Babies are especially susceptible to infection, because they cannot be vaccinated against pertussis until they are at least 2 months old. They may catch whooping cough from their parents, adult caregivers or other children.

What causes pertussis?

Pertussis is caused by Bordetella pertussis bacteria that can enter the respiratory system. If a person who is infected with the disease coughs or sneezes, tiny droplets of liquid containing the bacteria may be inhaled by a person who is nearby. Bacteria grow on the lining (mucosa) of the respiratory tract and increase the secretions of mucus.

A person with pertussis may be contagious even before symptoms appear and remain contagious for up to 2 weeks after coughing starts.

What are the symptoms of pertussis?

Early symptoms of pertussis may resemble those of the common cold. These symptoms may persist for 1 to 2 weeks.

They may include:

  • Slight fever
  • Mild or occasional coughing
  • Runny nose
  • Pause in breathing in babies

Symptoms of whooping cough after the first or second week has passed usually include:

  • Prolonged, repeated or violent coughing episodes (paroxysms) that recur intermittently for up to 10 weeks or more
  • Whooping sound when inhaling after the coughing stops
  • Vomiting
  • Exhaustion due to prolonged coughing

Symptoms begin to lessen after 4 weeks, although bouts of coughing can recur for months after onset.