This document discusses pertussis syndrome, caused most commonly by Bordetella pertussis. It is highly contagious and transmitted through coughing. While vaccination has reduced rates, cases are increasing as vaccination rates decline. Classic pertussis progresses through catarrhal, paroxysmal, and convalescent stages. Complications can be serious especially in young infants, including pneumonia, apnea, and encephalopathy. Treatment includes erythromycin to reduce symptoms and transmission. Prevention relies on vaccination with acellular pertussis vaccines.

1. Pertussis Syndrome
ETIOLOGY
• The pertussis syndrome includes disease caused by Bordetella
pertussis and certain other infectious agents.
• Classic pertussis, the whooping cough syndrome, usually is caused
by B. pertussis, a gram-negative pleomorphic bacillus with
fastidious growth requirements. Some cases of pertussis syndrome
are caused by other organisms, including Bordetella parapertussis,
which causes a similar but milder illness that is not affected by B.
pertussis vaccination.
• B. pertussis and B. parapertussis infect only humans and are
transmitted person to person by coughing.
• Asymptomatic carriage is rare.
 Adenoviruses have been associated with the pertussis syndrome.
• Dual infection with B. pertussis and adenovirus occurs more
frequently than expected.

2. EPIDEMIOLOGY
• The mean incubation period is 6 days.
• Patients are most contagious during the earliest stage.
• The annual rate of pertussis was approximately 100 to 200
cases per 100,000 population in the prevaccination era, and
presently it may be higher in developing countries.
• In the U.S., the incidence of pertussis has increased steadily
since the 1980s, with 5000 to 10,000 cases reported each
year. The peak age incidence of pertussis in the U.S. is
younger than 4 months of age-among infants too young to
be completely immunized and most likely to have the
complications of pneumonia and severe infection that are
associated with a high mortality.

3. • If vaccination rates are not high, pertussis
rates increase. In the United Kingdom, there
was a steady decline in the incidence of
pertussis until the late 1970s, when the
incidence increased dramatically as the rate of
vaccination declined. These data, a similar
episode in Japan at about the same time, and
the decline in the incidence of cases when
vaccines were first tested are major events
indicating the efficacy of vaccination.

4. CLINICAL MANIFESTATIONS
• Classic pertussis is the syndrome seen in most infants beyond the
neonatal period through school age.
• The progression of the disease is divided into
 catarrhal,
 paroxysmal,
 and convalescent stages.
 The catarrhal stage is marked by nonspecific signs (injection,
 increased nasal secretions,
 and low-grade fever) that last 1 to 2 weeks.
 The paroxysmal stage
 is the most distinctive stage of pertussis.
 Coughing occurs in paroxysms during expiration, causing young
children to lose their breath.

5.  This pattern of coughing is due to the need to dislodge
plugs of necrotic bronchial epithelial tissues and thick
mucus.
 It lasts approximately 2 to 4 weeks.
 The forceful inhalation against a narrowed glottis that
follows this paroxysm of cough produces the characteristic
whoop.
 Post-tussive emesis is common.
 The convalescent stage
o is marked by gradual resolution of symptoms over 1 to 2
weeks.
o Coughing becomes less severe, and the paroxysms and
whoops slowly disappear.
o Although the disease typically lasts 6 to 8 weeks, residual
cough may persist for months, especially with physical
stress or respiratory irritants

6.  Young infants
 may not display the classic pertussis syndrome;
 the first signs may be episodes of apnea.
 Young infants are unlikely to have the classic whoop,
 are more likely to have CNS damage as a result of hypoxia,
 and are more likely to have secondary bacterial pneumonia.
 Adolescents and adults with pertussis usually present with
a prolonged bronchitic illness that often begins as a
nonspecific upper respiratory tract infection. This illness is
not much different from pertussis in children, but generally
adolescents and adults do not have a whoop with the
cough, although they may have severe paroxysms. The
cough may persist many weeks to months

7. LABORATORY AND IMAGING STUDIES
• The diagnosis depends on isolation of B. pertussis, which is
usually accomplished during the early phases of illness by
culture of nasopharyngeal swabs on Regan-Lowe medium
or classically on glycerin-potato-blood agar medium
(Bordet-Gengou) to which penicillin has been added to
inhibit growth of other organisms.
• Direct fluorescent antibody staining to detect the organism
is technically difficult, dependent on the skills of the
technologist, and has low specificity.
• PCR is useful.
• Available serologic tests are not useful for diagnosis of
acute infection.

8. • A characteristic feature of pertussis in patients beyond the
neonatal age is an abnormally high absolute number and
relative percentage of lymphocytes in the peripheral blood.
• In classic B. pertussis-associated pertussis, lymphocytosis is
found in 75% to 85% of patients, although in young infants
the rate is much less.
• The WBC count may increase from 20,000 cells/mm3 to
more than 50,000 cells/mm3, consisting mostly of mature
lymphocytes.
• It is not unusual for physical and radiographic signs of
segmental lung atelectasis to develop during pertussis,
especially during the paroxysmal stage.
• Perihilar infiltrates are common and are similar to what is
seen in viral pneumonia.

9. DIFFERENTIAL DIAGNOSIS
• For a young child with classic pertussis syndrome,
the diagnosis based on recognition of the pattern
of illness is quite accurate. The paroxysmal stage
is the most distinctive part of the syndrome.
• Respiratory viruses such as RSV, parainfluenza
virus, and C. pneumoniae can produce bronchitic
illnesses among infants.
• In older children and young adults, M.
pneumoniae may produce a prolonged bronchitic
illness that is not distinguished easily from
pertussis in this age group

10. TREATMENT
• Erythromycin, given early in the course of illness, eradicates
nasopharyngeal carriage of organisms within 3 to 4 days and
ameliorates the effects of the infection.
• Treatment is not effective in the paroxysmal stage.
• When given to neonates younger than 4 weeks old, erythromycin
has been associated rarely with pyloric stenosis, but treatment is
still recommended because of the seriousness of pertussis at this
age.
• Azithromycin and clarithromycin can be given for a shorter duration
and are associated with fewer gastrointestinal adverse effects.
• TMP-SMZ may be beneficial as an alternative, but this remains
unproven.
• Pertussis-specific immunoglobulin may be effective in reducing the
symptoms of the paroxysmal stage.

11. COMPLICATIONS
• Major complications are most common among infants and
young children and include
 hypoxia,
 apnea,
 pneumonia,
 seizures,
 encephalopathy,
 and malnutrition.
 The most frequent complication is pneumonia caused by B.
pertussis itself or resulting from secondary bacterial
infection from S. pneumoniae, Hib, and S. aureus.
 Atelectasis may develop secondary to mucous plugs.

12. • The force of the paroxysm may rupture alveoli and produce:
 pneumomediastinum,
pneumothorax,
 or interstitial or subcutaneous emphysema;
epistaxis;
hernias;
 and retinal and subconjunctival hemorrhages.
 Otitis media and sinusitis may occur.

13. PROGNOSIS
• Most children do well with complete healing
of the respiratory epithelium and have normal
pulmonary function after recovery. Young
children can die from pertussis; 13 children
died in the U.S. from pertussis in 2003. Most
deaths occurred in unvaccinated children or
infants too young to be vaccinated.
• Most permanent disability is a result of
encephalopathy.

14. PREVENTION
• Active immunity can be induced with acellular
pertussis vaccine, given in combination with the
toxoids of tetanus and diphtheria (DTaP). Pertussis
vaccine has an efficacy of 70% to 90%; efficacy declines
with fewer vaccinations. The acellular vaccines contain
one or more antigens isolated from B. pertussis, such
as pertussis toxin, pertactin, or filamentous
hemagglutinins. Each preparation currently licensed
seems to provide equivalent protection. DTaP vaccine
is available for adolescents. Compared with older,
whole cell pertussis vaccines, acellular vaccines have
fewer adverse effects and local reactions

15. • Erythromycin and other macrolides are effective
in preventing disease in contacts exposed to
pertussis. Close contacts younger than 7 years old
who have received four doses of vaccine should
receive a booster dose of DTaP, unless a booster
dose has been given within the preceding 3 years.
They also should be given a macrolide antibiotic.
Close contacts older than age 7 should receive
prophylactic macrolide antibiotic for 10 to 14
days, but not the vaccine.