After the incubation period, typical whooping cough goes through three clinical stages. The first stage is the catarrhal stage, also called the pre-paroxysmal stage, during which the infectivity is the strongest. If treated promptly during this stage, the progress of the disease can be controlled. If the catarrhal stage is not effectively controlled, it then enters the paroxysmal stage. During the paroxysmal stage, the patient will experience episodic spasmodic coughing, with more severe episodes at night. During spasms, there will be neck vein distension, swollen and congested eyelids and face, and cyanosis of the lips. This stage can last up to two months. After the paroxysmal stage follows the convalescent stage, where the episodic spasmodic coughing gradually decreases and becomes less severe.