Inactive Tuberculosis: TB Germs That Don't Make You Sick — Yet

Up to 13 million people in the United States may be carrying tuberculosis germs without knowing it, CDC estimates. They don't feel sick, have no symptoms and can't spread TB to anyone. But without treatment, 1 in 10 of them will develop active TB disease — which can spread to others and can be deadly. The condition is called inactive TB, or latent TB infection.

Image from CDC's page on inactive tuberculosis.

Inactive TB vs. active TB disease

Inactive TB can turn into active TB disease at any time without treatment. If you have symptoms of TB disease, talk to a health care provider.

Who is at higher risk

Anyone can be infected, but the risk is higher if you:

• were born in or often travel to countries where TB is common, including in Asia, Africa and Latin America;
• live or used to live in large group settings where TB is more common, such as homeless shelters, prisons or jails;
• recently spent time with someone who has active TB disease;
• work where TB spreads more easily, such as hospitals, homeless shelters, correctional facilities and nursing homes.

Having had the TB (BCG) vaccine does not rule out inactive TB. People who live or work in higher-risk settings may be required to be tested regularly.

You don't need a test just because you spent time with someone who has inactive TB, since it can't spread. You should be tested if you spent time with someone who has active TB disease or its symptoms.

Testing

There are two tests for TB infection; your provider can help choose.

• TB blood test (interferon-gamma release assay, or IGRA): a blood sample is mixed with TB proteins to see how your immune system reacts. It is the preferred test if you had the BCG vaccine, because unlike the skin test it isn't affected by the vaccine — so tell your provider if you had it.
• TB skin test: a small needle puts testing material under the skin, and you return in two to three days to have the reaction checked.

A positive result means TB germs are in your body; further tests, such as a chest x-ray and a test of sputum (phlegm), show whether it is inactive TB or active disease. If a medical evaluation finds no evidence of TB disease, the diagnosis may be inactive TB. A negative result means you likely have neither.

Treatment

Treating inactive TB is the best way to keep from getting sick with active TB disease. Short, convenient treatments are available, and you and your provider choose which is best. Because there are fewer germs, treatment is much easier than treatment for TB disease — and taking the medicine as instructed can keep you from developing it. Public and private health plans may cover testing and treatment.

Sources

Based on "Inactive Tuberculosis," Centers for Disease Control and Prevention; a work of the United States government in the public domain. See also CDC's Think. Test. Treat TB campaign.