On average, it will take 9-10 days after being infected with pertussis to start to show signs and symptoms. At first, symptoms will look a lot like the common cold:
- Runny nose
- Nasal congestion
- Sneezing
- Red, watery eyes
- A mild fever
- Dry cough
Within two weeks, symptoms worsen and a severe cough develops that might:
- Become a series of violent coughs making it hard to breathe
- Be more severe at night
- Bring up thick phlegm
- Cause vomiting
- End with a high-pitched "whoop" sound when breathing in after a series of coughs
However, infants under 6 months old may not develop a whoop but may have temporarily stop breathing or have a bluish tint to their skin. Older children and adults also may not develop a whoop but will have a long lasting cough, or have symptoms like bronchitis or asthma. Vaccinated people might also have milder symptoms.