What is Latent Tuberculosis?

Susan Grindstaff

Latent tuberculosis is a term used to describe the condition where people have the tuberculosis germ in their bodies, but have not yet developed the disease. Unlike full-blown tuberculosis, this condition is not contagious, though it is an infection. In most cases, it does not develop into active tuberculosis.

Some doctors will prescribe medications to their patients who have latent tuberculosis.
Some doctors will prescribe medications to their patients who have latent tuberculosis.

To determine if a person has tuberculosis, the most common means of diagnosis is a skin test. In this test, tuberculosis bacteria are injected directly under the skin. This is usually done on the inner arm, because this area of skin is typically the most sensitive. If the site develops small red bumps within 48 hours, it generally means that the person has or has been exposed to the disease. To determine if the disease is active or latent tuberculosis, further testing is usually required, such as mucus cultures and x-rays.

Latent tuberculosis can be diagnosed from a skin test.
Latent tuberculosis can be diagnosed from a skin test.

Most of the time, latent tuberculosis does not become active. It is estimated that fewer than 10% of the latent cases will develop into active disease. People who have tested positive for latent tuberculosis should probably pay special attention to any developing symptoms. The symptoms of an active tuberculosis infection typically include nagging cough, low-grade temperature, and noticeable weight loss. Some people, even when the disease is active, exhibit no symptoms at all.

Latent tuberculosis does not have symptoms that require treatment; however, doctors may prescribe anti-tuberculosis medication. In many cases, this medication can keep the disease at the infection stage and it will not become active. This type of drug therapy typically lasts only about six months, but on-going checkups are usually required.

Unless latent tuberculosis develops into an active case, it is not considered particularly dangerous. If it does become active, there are many treatments available. Most of the time doctors will limit the activities of tuberculosis patients, as they often become physically weak. In addition, limited activity is sometimes necessary due to the contagious nature of the disease. With drug therapy, isoniazid is one of the more commonly prescribed medications.

Sometimes latent tuberculosis will activate into a more serious type of the disease. This type of tuberculosis is called “drug-resistant tuberculosis.” Though the exact reason is unclear, this type of tuberculosis is extremely resistant to medication. Once considered rare, according to the World Health Organization (WHO), incidence of this type of tuberculosis is steadily rising. In 2010, the WHO issued a report that indicated that one in four cases of tuberculosis were of the drug-resistant variety.

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