Pertussis (whooping cough)

DDx

Viral or bacterial pneumonia
Asthma
Other causes of chronic cough in adults, eg, postnasal drip, gastroesophageal reflux disease (GERD), tuberculosis, Mycobacterium avium complex (MAC)
Bronchiolitis, eg, respiratory syncytial virus (children)
Croup (children)
Infectious mononucleosis (both may have atypical lymphocytosis)

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