What Is Pertussis?

Pertussis, also known as whooping cough, is a highly contagious infection of the respiratory tract caused by the bacterium Bordetella pertussis. It is transmitted only by humans through close respiratory contact with someone who is infected, according to the CDC.

The number of pertussis cases in the U.S. peaked in the 1920s and 1930s, before a vaccine became available. At that time, the illness affected more than 250,000 people each year. The prevalence of pertussis has declined, but outbreaks continue to occur cyclically, with peaks occurring at three- to four-year intervals, the CDC says.

Illness on the rise

Since the 1980s, pertussis cases have been on the rise, especially among preteens and adolescents ages 10 to 19 years and in infants younger than 5 months old. And since 2010, data suggests cases are also on the rise for 7 to 10 year olds. The CDC's preliminary data reports show about 41,000 cases of pertussis in 2012. 

Adults are a major source of transmission of pertussis to infants and children. Pertussis in adults is often misdiagnosed as bronchitis, because symptoms in adults are milder than in children. Many adults were vaccinated decades ago and, although their immunity has decreased somewhat, they still have enough immunity to reduce the severity of the illness.

It usually takes a week to 10 days after a child has been exposed to the bacteria for symptoms to occur, says the CDC. The symptoms at first are similar to a cold: sneezing, runny nose, fever, and a mild cough. After one to two weeks, the coughing becomes worse. The violent spells of coughing may be followed by difficulty in breathing. Symptoms progress to severe coughing spells that can go on for a minute, followed by long, deep inhaled breath or "whoop" at the end of the coughing spasm. The coughing spells happen all day, but are often worse at night. Sometimes a person with pertussis will cough so hard that he or she vomits. This stage of the disease lasts one to six weeks, but can continue past that, according to the CDC.

Complications of pertussis

Common complications of pertussis include otitis media (ear infections), pneumonia, periods of not breathing (apnea), acute encephalopathy (a brain disorder caused by lack of enough oxygen to the brain), and difficulties getting enough nutrients because of vomiting. Some of these complications can be fatal. Infants under the age of 12 months have more serious illness from pertussis and are more likely to have complications and be hospitalized than older people.

The CDC recommends that children need five DTaP shots for maximum protection against pertussis. A DTaP shot is a combination vaccine that protects against three diseases: diphtheria, tetanus, and pertussis. The first three shots are given at two, four, and six months of age. Between 15 and 18 months of age, the fourth shot is given, and the fifth shot is given when the child enters school at four to six years of age. At regular checkups for 11- and 12-year-olds, a preteen should get a dose of Tdap (a slightly different form than the pediatric vaccine). The Tdap booster also contains tetanus, diphtheria, and pertussis. If an adult did not get a Tdap as a preteen or teen, then he or she should get a dose of it instead of the usual Td booster (tetanus and diphtheria) recommended for adults every 10 years. However, it can be given before the 10-year mark if necessary. It is especially important for pregnant mothers and grandparents to get Tdap before the infant is born. Always consult your doctor for advice.