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World Tuberculosis Day 2019: All you need to know about Latent and Active TB

Tuberculosis bacteria impact your immune system and continue to spread inside your body. ©Shutterstock

World Tuberculosis Day is celebrated every year with the intention of spreading awareness about TB. With this important day of the health calendar just around the corner, we give you a low-down on the latent and active versions of tuberculosis.

Written by Editorial Team |Published : March 23, 2019 9:56 AM IST

Every year on 24th March, World Tuberculosis Day is celebrated to spread awareness about the health, social and economic impacts of TB. According to a 2018 report by WHO, around 10 million people across the globe were diagnosed with TB in 2017 and 1.3 million people lost their lives due to this disease. In this survey, India was found to have the highest cases of TB in 2017 (24 per cent). This world body further cited that every day around 4,500 people die due to this life-threatening disease. However, combined efforts by the WHO along with various governments, civil society organizations, health-care providers and affected communities have helped to bring down the mortality rate of TB by 42 per cent so far.

It is a disease that occurs due to the Mycobacterium tuberculosis bacteria which target your lungs. You can catch these infectious bacteria from the air which can be contaminated when an infected person coughs or sneezes. Tuberculosis bacteria impact your immune system and continue to spread inside your body. If you have a weak immune system, you will develop TB as soon as you inhale the bacteria. However, if your body's defence mechanism is strong, you may not get the disease, even if the bacteria is inside your system. TB can be classified into two categories based on the nature of existence of these microorganisms in your body: Active and Latent.

WHAT IS LATENT TB?

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In case of Latent TB, your bacteria are asleep, and they will not pose any danger to your health. Latent TB bacteria are non-contagious. So you don t have to worry about passing on the disease to others. However, it is imperative that you consult your doctor as these bacteria can wake up in future, if left untreated.

Symptoms: There are no visible symptoms. According to the Centre for Disease Control and Prevention, only about 5 to 10 per cent of patients with Latent TB go on to develop Active TB. The absence of visible symptoms make it very difficult to diagnose Latent TB.

Diagnosis: Latent TB infection (LTBI) doesn't show up in chest X-ray. Currently, there are two tests to detect this TB infection: Tuberculin skin test (TST) and interferon-gamma release assays (IGRA). However, these tests have their own limitations. Both are incapable of differentiating between Active and Latent TB accurately and more so, in case of patients with HIV. Moreover, they are dependent on indirect markers of TB bacteria exposure. So, their prediction about the possibility of an LTBI becoming active is, in most cases, inaccurate. According to the WHO guidelines, patients suffering from HIV, end stage renal failure, silicosis (a lung disease caused by a mineral called silica), people who are in touch with other TB patients or are preparing for organ or blood transportation, have a high propensity to develop Active TB from the latent versions of the bacteria. So, they should be tested for LTBI from time to time.

Treatment: Unlike Active TB, which requires a four-drug regimen, Latent TB can be tackled with a single medicine. The recommended drug options include isoniazid, rifapentine and rifampicin. Your pulmonologist may ask you to be on isoniazid for 6-9 months, depending on your condition, or rifapentine plus isoniazid for 3 months. The 3-month regimen could also be isoniazid plus rifampicin or only rifampicin. Another important aspect of tackling LTBI is creating patient awareness about the necessity of this treatment and ensuring drug adherence.

WHAT IS AN ACTIVE TB?

Active TB bacteria make you ill without your knowledge. You may be passing on this deadly disease to others as well. As per the WHO estimates, a patient with Active TB bacteria can pass on this life-threatening disease to around 10 to 15 people due to close contact within a year. Active TB could be of two types: Drug sensitive TB (which gets cured by antibiotics) and Drug resistant TB (which doesn't get cured by a multiple number of drugs).

Symptoms: If you develop an Active TB disease, you may witness symptoms such as blood in the cough, night sweats, fever, or even weight loss. Since these symptoms are mild initially, it may delay the time you look out for care and cause the bacteria to spread in other parts of your body apart from the lungs.

Diagnosis: You may need to undergo a battery of tests to detect Active TB. The tests include TST, sophisticated blood test to observe the reaction of your immune cells to TB bacteria, imaging tests like chest X-ray or a CT Scan, and sputum tests.

Treatment: According to the WHO guidelines, drug sensitive TB patients should be under treatment for six months comprising two months of 'intensive' regimen and a four-month 'continuation' phase. The line of drugs used in the first two months include Isoniazid (H/Inh), rifampicin (R/Rif), pyrazinamide (Z/Pza), and ethambutol (E/Emb). For the continuation phase, isoniazid and rifampicin are continued. While undergoing treatment, patients need to take the prescribed drugs every day. The dosage depends on the body weight. According to the 2018 WHO guidelines, the drugs that should be used for the treatment of drug resistant TB includes fluoroquinolones, bedaquiline and a linezolid. They are prescribed along with other medicines. The treatment duration ranges between 18 to 24 months.

PREVENTIVE MEAUSURES

The preventive techniques for Latent and Active TB bacteria are similar as the only way to keep these bacteria at bay is to avoid coming in contact with them. Here, we share some preventive tips you can opt for to ward off this deadly disease.

Ventilate your household: TB is a disease that occurs when you inhale bacteria present in the air. In order to keep this fatal disease at bay, you should ventilate your room properly to eliminate the possibilities of breathing in the bacteria which causes TB.

Teach cough etiquette: If anyone at your home is suffering from TB, he or she should be educated about respiratory hygiene and cough etiquettes. This is because an infected person can spread this disease whenever he coughs or sneezes.

Avoid public transport: If you are suffering from TB, you should avoid using public transport as much as possible. This is because of the fact that chances of your bacteria spreading to others are very high.

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