infectious diseases
Pertussis
Introduction
Pertussis is a highly communicable disease occurring mostly in children and adolescents and caused by the gram-negative bacteriumBordetella pertussis. Symptoms are initially those of nonspecific upper respiratory infection followed by paroxysmal or spasmodic coughing that usually ends in a prolonged, high-pitched, crowing inspiration (the whoop). Diagnosis is by nasopharyngeal culture, polymerase chain reaction testing, and serologic assays. Treatment is with macrolide antibiotics. Pertussis is endemic throughout the world. Its incidence in the US cycles every 3 to 5 years. Pertussis occurs only in humans; there are no animal reservoirs. Transmission is mainly via droplets of respiratory secretions that containB. pertussis(a small, nonmotile, gram-negative coccobacillus) from infected patients, particularly during the catarrhal and early paroxysmal stages. The infection is highly contagious and causes disease in ≥ 80% of close contacts. Transmission by contact with contaminated articles is rare. Patients are usually not infectious after the 3rd week of the paroxysmal phase. Pertussis is a Childhood Vaccination that is increasing in incidence. In the US, the case rate in the 1980s was at an all-time low of about 1/100,000 population, which, by 2014, increased to about 10/100,000. The 2019 surveillance report by the Centers for Disease Control and Prevention (CDC) reported an incidence of 5.7/100,000 ( Immunity waning in previously vaccinated adolescents and adults Parents refusing to vaccinate their children (see Vaccine Hesitancy ) Such unprotected patients may become ill; furthermore, unprotected adolescents and adults are an important reservoir forB. pertussisand are thus often the source of infection for unprotected infants < 1 year (who have had the highest increase in annual incidence and the highest case fatality rate). Also, virulence of outbreak strains may be increasing. In the US in 2019, there were 18,617 pertussis cases and 7 deaths. The incidence per 100,000 was highest in infants < 6 months (76.5), and 4 of the 7 deaths occurred in infants < 1 year ( General reference ). Pertussis is also serious in older people. One attack does not confer lifelong natural immunity, but secondary attacks and infections in previously vaccinated adolescents and adults whose immunity has waned are usually mild and often unrecognized. 