Pertussis (Whooping Cough)
Occurrence
Pertussis, or whooping cough, is a highly contagious infectious disease caused by the bacterium Bordetella pertussis. Outbreaks of pertussis were first described in the 16th century. In unimmunized populations in the world, pertussis remains a major health problem among children, with an estimated 300,000 deaths per year due to the disease. In the United States, pertussis was one of the most common childhood diseases and a major cause of childhood mortality during the 20th century. With the widespread use of pertussis vaccine, the number of cases dropped from over 200,000 per year in the 1940s, to less than 3,000 cases per year in the 1980's.
Recently, however, pertussis has been on the rise. Nationally, nearly 29,000 cases of pertussis were reported in 2004, a 40-year high. Of these cases, 34% were in adolescents. (Read more about Pertussis cases in the US). California's pertussis cases have also been climbing, with a rise from 747 cases in 2004 to 2,100 in 2005 (read the California News Release).
Increases in pertussis in the United States are likely due to several factors, including declining immunity in persons who were vaccinated over 10 years ago.
Transmission
Pertussis bacteria live in the mouth, nose and throat of an infected person. Disease is spread though close contact when an infected person sneezes or coughs. It is most contagious during the first 2-3 weeks of infection: from the time the runny nose begins until 1-2 weeks after the onset of severe coughing spells.
Undiagnosed mild disease contributes to the spread of the illness among infants and young children Recent outbreaks have shown that older children, adolescents, and adults including parents may carry the disease which in its milder form is hard to recognize.
Symptoms
The incubation period for pertussis (the time between becoming infected and experiencing symptoms) is typically 7-10 days, with a range of 4-21 days. The course of the illness usually has 3 stages:
- In the first (catarrhal) stage, there is runny nose, sneezing, low-grade fever, and a mild cough that worsens over a period of 1-2 weeks.
- During the second (paroxysmal) stage, the patient has bursts (paroxysms) of numerous rapid coughs due to difficulty clearing thick mucus from the windpipe. At the end of each burst, there is a long inhalation usually accompanied by a high-pitched "whoop." Infants and young children are especially vulnerable during this stage. During coughing attacks they may turn blue, and appear very ill or distressed. Vomiting and exhaustion commonly follow the episode. This stage usually lasts 1-6 weeks.
- In the third (convalescent) stage, recovery is gradual as the cough disappears over 2-3 weeks, however many patients will continue to get cough attacks with later respiratory infections.
The disease is usually milder in adolescents and adults. Those who have been vaccinated can still become infected with B. pertussis but usually have milder disease. However, those with mild disease may still transmit pertussis to other people, especially infants who have not been completely immunized.
Young infants are at highest risk for developing pertussis, and for pertussis-associated complications. The most common complication, and the cause of most pertussis-related deaths, is pneumonia. Neurologic complications such as seizures and brain damage may occur. Most infants under 6 months of age require hospitalization when they develop pertussis, and dozens of deaths occur every year in young infants despite advanced medical care.
Diagnosis
Mild pertussis disease is difficult to diagnose clinically because its symptoms mimic those of a cold with cough. In moderate to severe disease, the diagnosis may be clear based on the paroxysms of cough, the "whoop", or the post-cough vomiting. The standard laboratory test for diagnosis of pertussis is isolation of B. pertussis by culture, using a swab specimen from the back of the nasal passages. Some laboratories use the nasal passage swab to look for pertussis DNA fragments or antibodies to pertussis. Blood antibody tests are less reliable for the diagnosis of pertussis.
Treatment
Antibiotics are most effective at relieving symptoms and shortening the course of the disease if started during the first (catarrhal) stage of illness. However, antibiotics started within 3 weeks after cough onset decrease infectiousness and limit the spread of pertussis from the patient to others. Therefore, a course of antibiotic treatment with erythromycin, trimethoprim-sulfamethoxazole, clarithromycin, or azithromycin is recommended to decrease infectiousness, even though it may have little impact on symptoms. Those with pertussis remain infectious for up to 5 days after starting antibiotic medication. Therefore, patients are advised to complete the course of antibiotics as prescribed, and to avoid close contacts (see definition below) especially with young children, during the first 5 days of their antibiotic treatment period.
Prevention of Transmission
Persons who have had close contact with an infectious case of pertussis are recommended to receive antibiotic medication to prevent infection. Close contact is defined as sharing toys, food, or utensils, face-to-face contact, direct exposure to cough, sneeze, or secretions, or sharing a confined space for over one hour. Antibiotics are effective for prevention if begun within 3 weeks of the exposure to pertussis. The use of preventive antibiotics is especially important in families with young children and in childcare and healthcare workers who could transmit infection to vulnerable populations such as infants, the immunocompromised, and those with chronic lung diseases.
Vaccine
- Babies and Young Children
- Pertussis vaccination begins in early infancy, but immunity is not complete until the series is complete. There is no single-component pertussis vaccine. Acellular pertussis vaccine (aP) is administered in combination with tetanus and diphtheria (TDaP). The recommended vaccination schedule is 2 months, 4 months, 6 months, and 15-18 months, plus a booster prior to school entry at age 4 or 5.
- Adolescents
- In 2005, two new pertussis booster vaccines, formulated for use in adolescents and adults, were approved by the FDA. BOOSTRIX® is indicated for ages 10-18 and ADACEL® is indicated for ages 11-64. Both vaccines contain tetanus, diphtheria, and acellular pertussis components (Tdap).
- Adolescents aged 11-18 years should receive a single dose of Tdap vaccine (BOOSTRIX® or ADACEL®) instead of Td (tetanus and diphtheria alone) for booster immunization, preferably at the 11-12 year old pediatric visit (Read the full ACIP recommendations for adolescents).
- Adults
- Adult immunization with Tdap vaccine (ADACEL®) is intended to prevent spread to infants and other vulnerable populations, and is recommended as described below. (Read the ACIP recommendations for adults)
- Adults aged 19-64 should receive a dose of Tdap vaccine to replace their next tetanus (Td) booster.
- Adults who have or anticipate having close contact with an infant <12 months of age (e.g. parents, child care providers, health care providers) should receive a single dose of Tdap, ideally at least one month before beginning close contact with the infant. An interval of 2 years or more since the most recent tetanus vaccine is suggested.
- Women should receive a dose of Tdap right after giving birth, if they have not previously received Tdap.
- Read the Vax Fax: Vaccine Update sent to providers on January 19, 2006.
San Francisco Vaccine Programs
The San Francisco Department of Public Health Adult Immunization Clinic is a fee-for-service travel and general adult immunization clinic located in the civic center area. It is a non-profit public health clinic whose mission is to provide accessible, informative, affordable, and convenient immunization services to San Francisco residents and visitors. The San Francisco Department of Public Health also supports the Vaccines for Children Program.
Useful Pertussis Links