|
|
Disease Overview Pertussis: Background
Pertussis: Overview
Prevention
Diagnosis & Treatment
Factors affecting under-recognition of disease
Laboratory confirmation of B. pertussis
Treatment
Reporting
For More Information
Following the introduction of immunization in the mid-1940s, pertussis incidence in the United States declined by more than 99 percent and to an all-time low of 1,010 cases in 1976. However, since then, an important increase in disease incidence has been documented, with more than 25,000 cases reported in 2005. In fact, experts now estimate that there may be as many as one million cases occurring in the US each year. The increase in pertussis cases is caused by many potential factors: • Under-vaccination in infants • Under- or misdiagnosis of both classic and mild pertussis • Waning Immunity from childhood pertussis vaccination. • Increased recognition of pertussis incidence among adolescent and adult populations, which contributes to the disease reservoir and has become an important source of disease transmission, especially to infants, who are more susceptible to disease complications back to top
Pertussis: Overview • Pertussis is a highly contagious disease of the respiratory tract that is caused by a gram-negative bacterium found in the mouth, nose, and throat of an infected person. An infected person has cough episodes that may end in vomiting or cause a "whoop" sound when the person tries to inhale. • Pertussis is primarily spread by direct contact with discharge from the nose or throat of infected individuals. Frequently, older siblings harboring bacteria in their nose and throat can bring the disease home and infect an infant in the household. • Classic (severe) pertussis, as defined by the World Health Organization (WHO), consists of at least 21 days of cough illness with paroxysms, associated whoops or post-tussis vomiting, and culture confirmation. Mild pertussis is any laboratory-confirmed pertussis disease that does not meet the criteria for classic disease. • For young children, pertussis disease can result in significant morbidity, hospitalization, serious long-term complications, and death. From 2000-2004, an average of 2,488 cases of pertussis was reported annually among infants less than 12 months old. Among these infants, 63% were hospitalized. Of the 100 pertussis-related deaths reported from 2000-2004, 90% were among infants less than 4 months old and 76% were younger than 2 months of age. • While often considered a childhood disease, pertussis occurs at any age; in fact, two-thirds of pertussis cases in 2005 were reported in adolescents and adults. • Studies indicate that, when the source of a case can be traced, mothers are responsible for nearly one-third of whooping cough cases in infants. Other family members, such as fathers and older siblings can also be sources of pertussis infection in infants. • Recent outbreaks in hospital settings have demonstrated the need for Tdap boosters for health care workers in order to prevent the spread of pertussis. Health care workers are not only susceptible to whooping cough complications, but they are also in a position to expose vulnerable individuals to the disease, including unvaccinated infants, who are at risk for serious complications, and those with compromised immune systems. Immunization for Children
The acellular, or DTaP (diphtheria-tetanus-acellular pertussis), vaccines are very effective in preventing classic pertussis and have fewer adverse reactions than the whole-cell DTP vaccines that was previously used. The vaccine for pertussis is usually combined with vaccines for diphtheria and tetanus. Although mild reactions, such as a sore arm or fatigue, are common with the DTaP vaccine, moderate reactions are uncommon and severe reactions, such as a major allergic reaction, are very rare.
Five licensed acellular pertussis vaccines are currently available for use in children in the United States: • DAPTACEL (sanofi pasteur) • Tripedia (sanofi pasteur) • Infanrix (GlaxoSmithKline) • Pediarix (GlaxoSmithKline) • TriHibit (sanofi pasteur) All of these vaccines are combined with diphtheria and tetanus toxoids. Pediarix also contains hepatitis B and inactivated polio vaccines. In addition to protecting against diphtheria, tetanus, and pertussis, TriHibit also protects against haemophilus influenzae type B.
DTaP should be administered to children for protection against pertussis, diphtheria and tetanus at: • 2 months (1st dose may be given as early as 6 weeks of age) • 4 months • 6 months • 15-18 months (4th dose may be given as early as 12 months of age) • 4-6 years Immunization for Adolescents and Adults
Protection against pertussis from pertussis vaccines typically wanes from 5 to 10 years after the last childhood vaccination. DTaP is not approved for use in children older than 7 years. New booster vaccines are now available for adolescent and adult use in the United States – these are known as Tdap (tetanus-diphtheria-acellular pertussis).
Of the two Tdap preparations available, one can be used for both adolescents and adults, and the other has been approved for use only in adolescents: • ADACEL (sanofi pasteur) for use in persons age 11–64 years • Boostrix (GlaxoSmithKline) for use in persons age 10–18 years
The Center for Disease Control and Prevention’s (CDC) Advisory Committee on Immunization Practices (ACIP) recommends that adolescents 11 and 12 years of age receive Tdap in place of the tetanus-diphtheria (Td) booster typically given, and that adolescents 13 through 18 who missed the 11- to 12-year dose of Td receive a Tdap booster. Adolescents ages 11 to 18 who have already been vaccinated with Td are encouraged to receive a dose of Tdap to further protect against pertussis, if at least 2 years have passed since their last dose of Td. It is also recommended that adults ages 19-64 receive a single dose of Tdap for pertussis protection, especially those who have close contact with infants less than 12 months of age.
Immunization for Health Care Workers
CDC recommends that Tdap boosters be given to health care workers in hospitals and/or ambulatory care settings in place of the previously recommended Td booster. Priority should be given to health care workers in contact with infants under 12 months of age. Recent outbreaks in hospital settings have demonstrated the need for Tdap boosters for health care workers in order to prevent the spread of pertussis.
Health care workers are not only susceptible to whooping cough complications, they are also in a position to expose vulnerable individuals to the disease, including unvaccinated infants, who are at risk for serious complications, and those with compromised immune systems.
In September 2003, a pertussis outbreak was reported in the pediatric unit of a Pennsylvania hospital. It is suspected that a pediatrician caught pertussis from an infected infant patient and spread the infection to at least 7 colleagues and 2 children that he examined. At the time of this outbreak, Tdap boosters were unavailable, but vaccinating health care workers with the now recommended Tdap booster vaccine could prevent similar outbreaks in the future.
Immunization of Pregnant Women
CDC recommends that pregnant women who have not already received a dose of Tdap, and 2 years have lapsed since their last Td dose, receive the Tdap booster immediately after delivery, before discharge from the hospital or birthing center. In special situations, such as a pertussis outbreak or exposure to an infected person, health care workers may choose to administer Tdap instead of Td during pregnancy to add protection against pertussis. In these circumstances, it is preferred that Tdap be administered during the second or third trimester of the pregnancy.
Symptoms
Classic pertussis is usually associated with a high white blood cell count with lymphocytosis, with an absolute lymphocyte count of 20,000 or more. Children with mild pertussis may not have lymphocytosis.
After exposure to an infected person, the incubation period is usually 7 to 10 days, although it can range from 4 to 21 days before symptoms start. Classic pertussis has three stages – catarrhal, paroxysmal, and convalescent.
Catarrhal
During the catarrhal stage, symptoms are very similar to those of a cold – runny nose, sneezing, low-grade fever, and a mild, nonproductive, occasional cough.
Paroxysmal
After a week or two, the illness moves on to the paroxysmal stage, when the patient experiences severe spasms of quick, short, coughs like a machine gun without breathing in between coughs. Patients often gag and gasp and sometimes expel thick mucus. After the attack, patients typically strain to inhale, which is when they make the signature, high-pitched whooping sound. This may be followed by vomiting and exhaustion.
Convalescent
When patients start the convalescent stage, they recover gradually. They cough less and less often and their coughs are less severe. The coughing attacks may last for many months in the "classic illness" or just a few days in the mild form of the disease.
Pertussis disease is generally under-reported and under-diagnosed for several reasons. Because a pertussis vaccine exists in the United States, there may be a misconception that immunization has eliminated the disease. With more than 25,000 cases reported in 2005 – which may represent only a percentage of the actual number of cases – it is clear that awareness must be increased because pertussis is much more prevalent than is currently perceived.
The prevalence of mild disease is another factor that plays a role in the under-recognition of pertussis. Cases of pertussis frequently go undetected because the well-known symptoms of the classic illness are not always present. Mild disease – which is very hard to diagnose because it resembles the common cold – appears to be one of the factors responsible for the infection of un-immunized and under-immunized infants and young children in the United States, as well as the continuous transmission and circulation of the disease. Undiagnosed mild disease in children, adolescents, and adults has become an important source of disease transmission in the United States.
Confirmation of pertussis is a diagnostic challenge for clinicians because current diagnostic tests make culture or antigen detection difficult. Improved and more rapid diagnostic tests would allow office-based diagnosis and effective intervention with treatment.
Because laboratory confirmation of pertussis can be difficult, clinicians typically make a diagnosis on the basis of characteristic manifestations of prolonged paroxysmal coughing with supportive associated findings, such as inspiratory whoop, post-tussive emesis, and lymphocytosis. However, laboratory confirmation of nasopharyngeal specimens obtained using the proper technique may be useful in young infants as well as atypical or mild cases.
Antigen Detection:
• The traditional laboratory method for diagnosis is isolation of B. pertussis by culture. • Increasingly, the favored approach for laboratory confirmation of pertussis is polymerase chain reaction (PCR), preferably in conjunction with culture. In many labs across the country, including the New York State Health Department, PCR is becoming the most used method of diagnosis. • Serological testing yields difficult-to-interpret results and is not widely used. • Another method of B. pertussis identification is the direct fluorescent antibody (dFA) technique. However, it is no longer considered useful for diagnosis as some data show that dFA testing on nasopharyngeal samples shows low sensitivity and variable specificity. Hospitalization for supportive care is often required in infants and others with potentially severe pertussis. Antimicrobial agents given during the catarrhal stage may lessen disease symptoms. When given after the catarrhal stage, antimicrobial agents have little or no effect on the course of illness but are still recommended to reduce the possibility of disease spread to others.
According to the American Academy of Family Physicians Practice Guidelines (updated July 15, 2006), Erythromycin, clarithromycin (Biaxin), and azithromycin (Zithromax) are preferred for the treatment of pertussis in persons one month and older. In those younger than one month, the use of erythromycin and clarithromycin is not recommended, and azithromycin is preferred. For patients two months and older, an alternative agent, trimethoprim/sulfamethoxazole (Bactrim, Septra), is available.
Reporting All cases of pertussis should be reported immediately to your state's health department. Information on this procedure can be found in the Pertussis Reporting Guide.
For More Information, go to:
American Academy of Pediatrics (AAP): www.aap.org
Immunization Action Coalition (IAC): www.immunize.org
National Foundation for Infectious Diseases (NFID): www.nfid.org/whoop
Advisory Committee on Immunization Practices (ACIP): www.cdc.gov/nip/acip
Sources:
Bibliography/Further Reading:
back to top The information contained in the Pertussis Information Center Web site should not be used as a substitute for the medical care and advice of your health care provider. There may be variations in treatment that your health care provider may recommend based on individual facts and circumstances. Pertussis.com is an educational project by the National Association of Pediatric Nurse Practitioners (NAPNAP).
|