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Opinions differ as to why a clinically characteristic disease
like pertussis was not described prior to de Baillou's description.
Kloos and colleagues (1981) suggest that the absence of a clinical
description of pertussis prior to the sixteenth century may reflect
adaptation of a close genetic variant of B. pertussis to
humans as recently as five centuries ago. Holmes (1940), in
contrast, as noted by Mortimer (1988), attributed the lack of a
prior description to an earlier preoccupation of physicians with
other serious infections such as plague, smallpox, and typhus and
to the possibility that they may have relegated the care of
pertussis patients to ''old women."
The incubation period of unmodified pertussis averages 7 to 14
days, with a maximum of 21 days (Berkow, 1987). Clinically,
pertussis can be divided into three sequential stages: the
catarrhal, paroxysmal, and convalescent stages (Cherry et al.,
1988; Mortimer, 1988). The onset of illness in the early catarrhal
stage is subtle and is generally indistinguishable from that of a
minor upper-respiratory infection. Early symptoms include
rhinorrhea, mild conjunctival injection, sneezing, anorexia,
listlessness, and a hacking nocturnal cough that gradually becomes
diurnal as well. Fever is usually absent. During this time,
coughing continues to increase in frequency and intensity and, by 7
to 10 days after the onset of illness, becomes explosive and
episodic, heralding the onset of the paroxysmal stage. The disease
is most infectious during the catarrhal stage, after which
infectivity gradually declines.
The paroxysmal stage, which lasts 1 to 4 weeks, is dominated by
severe episodes of coughing, which can occur 10 times or more in a
24-hour period. Each paroxysm is characterized by five or more
rapid short coughs followed by a deep hurried inspiration. It is
this hurried inspiration through a narrowed airway that produces
the characteristic whoop.
Paroxysms are thought to be caused by efforts to expel the thick
mucus that characteristically accumulates in the tracheobronchial
tree. During such episodes, copious amounts of this mucus are
expelled, often causing vomiting and, in infants, choking spells
and cyanosis. The child is often exhausted following a paroxysm,
although he or she can appear happy and relatively normal between
episodes. Multiple paroxysms tend to occur within