Cause of TB - TB bacteria

What is the cause of TB?

TB is caused by a type of bacteria whose scientific name is Mycobacterium tuberculosis.

TB is an abbreviation, that is a shortened form, of the word Tuberculosis. Tuberculosis is a disease and TB is how people often refer to Tuberculosis.

How long do TB bacteria stay alive?

The bacteria that cause TB can sometimes stay alive in the air for a few hours, especially in small places with no fresh air. Fresh air and sunlight make it harder for the bacteria to stay alive. The fresh air scatters the bacteria and the sunlight kills them.1"Get the Facts About TB Disease", CDC

How is TB spread

The bacteria are spread from person to person through microscopic droplets that are released into the air when a person who already has TB coughs, speaks, sneezes, spits laughs or even sings.

Then someone else nearby inhales the droplets that have been expelled and which contain the bacteria.

Does everyone who inhales the bacteria become ill?

The bacteria that cause TB

The bacteria that cause TB

Not everyone who inhales the bacteria becomes ill. In many healthy people the immune system is able to destroy the bacteria that cause TB. In some cases the bacteria infect the person's body but don't cause any symptoms. This is known as having latent TB. The bacteria may then after a period of weeks, months or even years, begin to cause the symptoms of TB. This is known as having active TB.

People with latent TB do not feel sick and cannot spread the TB bacteria to other people.

Why do some people get TB when others don't

It is not known why some people who are exposed to the bacteria that cause TB get infected with the bacteria and get TB when other people don't. The chance of becoming infected depends mainly on the quantity of infectious droplets in the air, and the length of exposure to an infectious person. The closer the infectious person is, and the longer the length of exposure, the higher the risk of becoming infected.

Can TB be cured?

TB can be cured in most people by the person with TB taking a combination of TB drugs. Once the person has been taking the drugs for a few weeks they are no longer infectious and cannot pass the TB bacteria on to other people. Saying that TB is contagious is another way of saying that TB is infectious.

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This page was last updated in December 2019.
Author Annabel Kanabus

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