c. Communicability. A patient is infectious for as long as he discharges
tubercle bacilli. The degree of communicability depends on several factors: density of
contaminated droplets in the air; coughing habits of the patient; and air circulation and
fallout in the particular environment. During the period when the patient is infectious, an
uninfected person needs to inhale at least one infectious droplet nucleus to become
infected. The healthy person must inhale tubercle bacilli so that they are carried far
down the airways to a point in the lung where fixed mononuclear phagocytes can pick
the droplets up and droplet intracellular multiplication can begin. The infected patient's
sputum, if it carries enough bacilli, is a source of infection when the patient coughs or
sneezes thus spraying the air with bacilli. If there are several people living close
together, just one of them being infected with tuberculous bacilli can spread the disease
to the others.
d. Immunity. How susceptible people are to infection in general is influenced
by several factors: age, sex, race, nutrition, and general health. In regard to
tuberculosis, children under 3 years old are the most susceptible. There have been
fewer cases of tuberculosis in children since bovine tuberculosis has been controlled.
(Children are no longer consuming infected dairy products.) There are fewer cases of
tuberculosis among Caucasians than among Blacks and American Indians, but no one
is sure of the reason. Perhaps through the years only Caucasians most resistant to
tuberculosis have survived. In general, possibly Caucasians live in better environments
and eat more nutritionally balanced meals thus giving them better health. The number
of cases of tuberculosis is usually greater among city dwellers than among those who
live in the country. City people live closer together; therefore, one infected city dweller
will probably come in contact with and pass on the tuberculosis infection to more people
than a country dweller.
From the time of infection, it takes about four to eight weeks for a person to
develop tuberculosis. The person may have no symptoms, mild symptoms, or
nonspecific symptoms. If there are symptoms, these are the most common:
c. Weight loss.
d. Irregular menses.
e. Low grade fever.
f. Night sweats.