IPA: /pərˈtʌsɪs/
KK: /pərˈtəsɪs/
A highly contagious bacterial infection that causes severe coughing fits, often referred to as whooping cough.
The doctor diagnosed the child with pertussis after observing the characteristic cough.
Pertussis is derived from the Latin "per-" (meaning through) and "tussis" (meaning cough). The term refers to a severe cough that is characteristic of the disease, indicating a cough that goes through or persists.
Think of a cough that goes 'through' ('per-') and is very intense ('tussis') — that's why pertussis refers to a severe cough.