
pneumonia due to mycoplasma pneumoniae
its incidence in the membership of a co-operative medical group
ruth mcmahan, edmund r. clarke, william a. maccoll, and j. thomas grayston
a total of 1051 cases of pneumonia occurred in
72,992 persons who were members of a medical
co-operative in the period december 1, 1963, to
december 31, 1964.  the annual rate of pneumonia
was 12.9 per 1000.  isolation of mycoplasma pneumoniae
from throat swabs was attempted in over
half the cases reported, and paired blood specimens
were obtained in one third.  on the basis of laboratory
examination of these specimens, the incidence
of clinically recognized pneumonia due to m. pneumoniae
was between 1 and 1.5 persons per 1000
per year.
although peak rates of pneumonia occurred under
five years of age (45 per 1000) pneumonia due to m.
pneumoniae was uncommon in this age group.  it
was most common in children five to nine years old,
and was frequently the cause of pneumonia in adolescents
(ten to nineteen years of age).  the rates in
children in primary school was twice the average
incidence.  m. pneumoniae pneumonia also differed
from the pneumonias of other etiology in that it
occurred throughout the year, with no seasonal excess
whereas total pneumonia showed a predominance
in winter.
the typical clinical syndrome of the pneumonias
in which m. pneumoniae was isolated was one of
prominent systemic manifestations of headache and
fever, but few respiratory symptoms occurred except
cough.  upper-respiratory-tract complaints and an
elevated white-cell count were much more frequent
in the other pneumonias.  the patients with m.
pneumoniae pneumonia were almost never hospitalized
but suffered significant absenteeism.  they
came from larger families, usually with children of
school age.  reporting physicians were usually correct
in diagnosing these pneumonias as "atypical" or "viral."
