Tuberculosis (TB)

Tuberculosis (TB) is an infectious disease caused by a type of bacteria called Mycobacterium tuberculosis. TB usually affects the lungs, but it can affect the brain, bones, lymph nodes, joints, kidneys, and other parts of the body. It's one of the most common diseases in the world, but it's relatively rare in the U.S. There are only about 2-4 cases in Whatcom County each year.

  • Not everyone who is infected with TB bacteria gets sick. Some people have a latent TB infection, which means they don't have symptoms. People with active TB disease show the signs and symptoms of TB.
  • TB isn't spread easily. You have to spend a lot of time in close contact with a person with active TB disease to get it. TB isn't spread easily outdoors because air flows freely and sunlight kills the TB bacteria.
  • People who are at higher risk for TB are:
    • People who live with someone who has active TB disease.
    • People who have traveled to or were born where TB is common.
    • People who have a health condition.
  • We work to prevent the spread of TB in our community by testing people who could have the disease and making sure that people with active TB disease get treatment.
  1. Latent TB Infection
  2. Active TB Disease

The first phase of TB infection happens when a person breaths in TB bacteria during exposure to a person who has TB disease. In healthy people, the TB bacteria are contained by the immune system and become dormant (asleep) in their body. This phase - called latent TB Infection - can last a long time, often decades.


A person with TB infection has no symptoms. An X-ray of their chest is normal.

How It Spreads

TB infection is not contagious during the latent phase. Because TB bacteria are dormant (asleep) and not active, a person with latent infection cannot spread TB or infect others.

Screening & Testing

Two types of TB tests are most often used to check for TB infection:

  • TB blood tests.
  • Tuberculin skin test.

Only a positive TB test detects latent TB Infection.

Prevention & Treatment

People with latent TB infection should complete treatment for latent TB Infection to prevent getting active TB disease. It also prevents them from exposing other people to TB.

Latent TB Infection is treated by taking 1-2 medications for 3 to 4 months.