Pertussis, or whooping cough, is a contagious disease involving the lungs and airways. It is caused by a bacteria.

HOW IT SPREADS: People get pertussis by breathing in droplets from the nose and mouth of someone who is already infected. Older children and adults may have milder disease and may spread the disease to unimmunized infants and young children. An infected person is most contagious at the beginning of the disease. If untreated, an infected person can spread pertussis for up to 3 weeks after coughing starts. Antibiotic treatment limits contagiousness to five days after treatment is started.HOW IT STARTS: Symptoms usually start 5 to 10 days after exposure to someone with the disease, but may take as long as 20 days to start.SYMPTOMS: Pertussis begins as a mild illness like the common cold. Sneezing, runny nose, low-grade fever and mild coughing progress to severe coughing. Some people have episodes of rapid coughing followed by a high-pitched whoop as they take a deep breath. Not everyone with pertussis has a whoop, especially infants.TREATMENT: Antibiotics are helpful in reducing the spread of the disease.