Pertussis is also known as whooping cough. Patients may have no specific symptoms at the beginning, only runny nose, sneezing, mild fever and coughing. But the cough can become increasingly severe and intensified, preventing the patient from eating and breathing. The bacteria can infect the lungs, which can lead to convulsions and unconsciousness in severe cases. Pertussis is highly contagious that anyone can be infected, but infants and young children under six months of age are at higher risk of serious complications (and even death).