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What is the difference between latent and active tuberculosis?

The difference between latent and active tuberculosis (TB) is that people with latent TB have been infected but don't get sick, where people with active TB show signs and symptoms of the infection. People with active TB often have a cough for multiple weeks, bloody sputum, fevers, weight loss and other symptoms. They tend to be very sick and can die without treatment. People with latent TB have been infected with the bacteria but their body has been able to fight to keep the bacteria from making them very sick. Some people with latent TB may never become sick, but some do. People with latent TB do not spread TB to others and don't feel sick unless they progress to having active TB.

If you've been infected with tuberculosis (TB), usually you won't show any symptoms at all. That's because your immune system has killed most of the TB bacteria, and the few survivors are locked up inside your white blood cells. This is called latent tuberculosis, and only a tuberculosis skin test or blood test can detect it. You're not contagious, and in 90 to 95 percent of cases, you could carry the tuberculosis infection all your life and never get sick from it. However, if your immune system weakens, the dormant TB bacteria could start to grow and develop into active TB disease.

If you have active tuberculosis disease, the TB bacteria have begun to multiply. You will feel sick, usually with a severe cough lasting three weeks or more. Active TB is contagious, and it can be fatal if not treated.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.