Whooping cough (pertussis) is a highly contagious respiratory tract infection. In many people, it’s marked by a severe hacking cough followed by a high-pitched intake of breath that sounds like “whoop.”

Before the vaccine was developed, whooping cough was considered a childhood disease. Now whooping cough primarily affects children too young to have completed the full course of vaccinations and teenagers and adults whose immunity has faded.

Deaths associated with whooping cough are rare but most commonly occur in infants. That’s why it’s so important for pregnant women — and other people who will have close contact with an infant — to be vaccinated against whooping cough.

Once you become infected with whooping cough, it takes about seven to 10 days for signs and symptoms to appear, though it can sometimes take longer. They’re usually mild at first and resemble those of a common cold:

• Runny nose
• Nasal congestion
• Red, watery eyes
• Fever
• Cough

After a week or two, signs and symptoms worsen. Thick mucus accumulates inside your airways, causing uncontrollable coughing. Severe and prolonged coughing attacks may:

• Provoke vomiting
• Result in a red or blue face
• Cause extreme fatigue
• End with a high-pitched “whoop” sound during the next breath of air

However, many people don’t develop the characteristic whoop. Sometimes, a persistent hacking cough is the only sign that an adolescent or adult has whooping cough.

Infants may not cough at all. Instead, they may struggle to breathe, or they may even temporarily stop breathing.

Call your doctor if prolonged coughing spells cause you or your child to:

• Vomit
• Turn red or blue
• Seem to be struggling to breathe or have noticeable pauses in breathing
• Inhale with a whooping sound