Pertussis, a disease caused by a bacterial infection, leads to an increase in lymphocytes beyond normal levels during the acute phase. If secondary infections occur, the relative lymphocyte count may decrease. The examination of these white blood cells is only an auxiliary test; culturing the pathogen or using fluorescent antibody staining are also viable methods that can definitively diagnose a pertussis infection. This condition can cause paroxysmal, spasm-like coughing, and some may exhibit a barking cough. Once diagnosed, medication should be selected according to the treatment course, with regular follow-ups.