Whooping Cough (Pertussis)
Terry Murphy
ED Medical Director
Samaritan Hospital
Pertussis is a very highly contagious respiratory tract infection caused by a bacterium named Bordatella pertussis. A closely related bacterium, Bordatella parapertussis, also produces a very similar illness. Because of the disease symptom similarities; the two illnesses are both commonly referred to as Whooping Cough.
Since humans are the sole reservoir for both Bordatella pertussis and Bordatella parapertussis, the disease is spread only from human to human, through the transmission of infected mucous particles, by aerosolized droplets during coughing or sneezing, or by direct contact with the infected mucous. Transmission rates from human to human via contact are estimated to be as high as eighty to ninety percent.
The illness known as Pertussis was first identified in the 16th century but the causative organism (bacterium) was not identified until 1906. Before the advent of vaccinations, pertussis was a major cause of death and disability among infants and children, but infections have decreased by more than 99 percent since the routine use of vaccinations in the 1940’s. However, in the U.S., since the early 1980’s, there has been an increasing incidence of Pertussis, with outbreaks occurring cyclically, every three to four years. From 1997 to 2000, the incidence in the U.S. was seven to eight thousand infections per year (3.7 cases per 100,000 people). Worldwide, there are an estimated fifty million infections per year. Both genders are equally affected, and seventy-five to eighty percent of infections occur in populations younger than twenty years of age.
While Pertussis gets its common name from the characteristic sounding cough it produces in adolescents and young adults; the infection is actually much more common in infants, who do not usually have the characteristic cough. The Pertussis infection usually goes through four stages:
The incubation period after which a person has come in contact with the pertussis bacterium and those organisms multiply in number in the nose, throat and upper airways (trachea and bronchioles). This stage lasts for three to twelve days and is not usually associated with any symptoms.
The initial symptoms or catarrhal stage is indistinguishable from a common upper respiratory infection (URI) with nasal congestion, runny nose, sneezing and low grade fever; however, fever is rarely a prominent feature of Pertussis at any stage of the disease. This stage lasts a week or two, and is actually when the person is most contagious to others.
The paroxysmal stage is when a person has the classic paroxysms of intense coughing lasting up to several minutes followed by a loud “whoop” as the child or adult forcefully breathes in air that has been coughed out. It is very common in children for a coughing paroxysm to be followed by vomiting. Infants up to six months typically do not have a characteristic cough; but may have dangerous spells of apnea (breath holding) and may turn blue. During this stage of 1-2 weeks, the upper respiratory infections symptoms improve.
The last or convalescent stage may last for several more weeks and is characterized by a persistent, intermittent, cough. People are no longer “infectious” during the convalescent stage.
Infants under age 6 months, premature infants and infants born with heart, lung or neuromuscular abnormalities are at greatest risk for death; whereas almost all older children and adults have a mild illness. In fact, in most adults, Pertussis appears very similar to, and is often diagnosed as, a bad URI or bronchitis.
When the diagnosis is suspected, a swab of mucous from the back part of the nasal cavity should be obtained for analysis and culture. While results of the swab analysis are not usually known immediately; patients suspected of having Pertussis should be treated before culture results are known.
Experts recommend treatment with antibiotics during the initial phase to eradicate the bacteria and reduce symptoms, and during the paroxysmal phase to reduce spread of the illness. Typically antibiotics prescribed include erythromycin products (e.g. Biaxin or Zithromax) or sulfa medications (e.g. Bactrim). Also, since there is conclusive evidence that older siblings and parents are the primary source of infection of younger infants, all household and other close contacts should be treated with antibiotics when the diagnosis is culture proven, to prevent further spread of the disease outbreak.
Hospitalization should be considered for infants under 6 months; premature infants or infants with heart, lung or neuromuscular disorders; as well as children with severe paroxysms of coughing. When death or serious illness (e.g. pneumonia or seizures) occurs, it is usually an unvaccinated infant or one too young for vaccination.
It is well recognized that active immunization increases resistance to Pertussis infection. In fact, prevention of a Pertussis infection can be almost guaranteed with appropriate vaccination; and if an infection occurs, the symptoms are usually much more benign. Current vaccination recommendations for Pertussis prevention are immunization at 2, 4, 6 and 15 to 18 months; with a booster between ages 4 – 6 years. Protection against Pertussis after immunization wanes after three to five years, and is not present after ten to twelve years. Therefore, since 2005 it has been recommended that adolescents age ten to eighteen years of age receive an additional booster.
Other prevention measures include:
• frequent hand washing – especially when caring for infected people,
• respiratory isolation of infected individuals, and
• antibiotic prophylaxis of all close contacts.
This article is intended to provide useful information, not medical advice. This information cannot, and is not meant to, replace consultation with your physician regarding your individual circumstances.