How is tuberculosis spread?
is usually spread when someone inhales the airborne TB
bacteria which is normally carried on droplet nuclei.
The bacteria, because of its small size, is able to avoid
most of the body's defense mechanisms and reaches the
lower respiratory tract lodging in the aveoli of the
Who may be at risk of becoming infected with TB?
who comes into contact with someone with active TB. This
may include friends, family, doctors, nurses, radiologists,
home health aides, prison guards, etc. In addition, those
who are immunosuppressed have a greater risk of developing
the clinically active disease.
Where are outbreaks of TB presently occurring?
A: The spread
of TB is now considered to be at an epidemic stage throughout
many areas of the US with certain regions experiencing
a 30+% increase in active cases per year. The Centers
for Disease Control (CDC) reports that outbreaks of TB
are occurring in health care facilities, shelters for
the homeless, drug treatment facilities, and especially
How long can the TB bacteria remain airborne?
of its small size, the bacteria is virtually weightless
and can remain suspended in air almost indefinitely.
Due to this characteristic, it is able to be carried
by normal air currents throughout a room or facility.
Is there concern for transmission of TB once the
bacteria comes in contact with a surface?
only if the particle can once again become airborne.
The CDC states that non-critical items (those that either
do not ordinarily touch the patient or those that touch
intact skin) do not transmit tuberculosis infection.
What happens to the droplet nuclei when it comes
in contact with a surface?
this small normally come in contact with walls and ceilings.
Once deposited, they are imbedded or attached to the
surface by a process called molecular adhesion. Scrubbing
usually becomes the only way to remove them. After a
period of time, the droplet nuclei evaporate and the
TB bacteria eventually ceases to be virulent.
What are the chances of a susceptible person becoming
infected with TB?
A: That probability
depends upon the concentration of infectious droplet
nuclei in the air and the amount of time spent in the
How much risk is a person in a health care facility?
A: Many factors
vary that risk, some considerations are the population
served, job category, and where within the facility the
worker functions as well as the amount of time spent
with TB patients.
Is there a greater risk in some areas than others?
may be a higher risk where patients with TB are provided
care before any positive diagnosis for TB takes place.
This would include areas such as clinic waiting areas
and emergency rooms. Other areas of risk would be any
place where an active TB patient spends time or receives
How concerned should health care workers be if they
function in settings where those diagnosed with HIV
A: They should
be particularly alert to prevention of TB transmission,
especially if, for example, medical procedures which
induce coughing are used.
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