Tuberculosis – Causes, Symptoms, Treatment, and Prevention.

Definition

Tuberculosis (TB) is a disease which in humans is usually caused by bacteria called Mycobacterium tuberculosis (M. tuberculosis). TB is an abbreviation of the word Tuberculosis and is how people often refer to the disease. Bovine TB is a disease caused by similar bacteria called Mycobacterium bovis (M. bovis). Bovine TB mainly affects cattle but can also affect humans.

Just a few years ago it was believed that TB was an old disease, and that it was no longer a problem in humans. But now because of such issues as drug resistance and HIV, it has become a major problem again.

History

On March 24, 1882, Dr. Robert Koch announced the discovery of Mycobacterium tuberculosis, the bacteria that cause tuberculosis (TB). During this time, TB killed one out of every seven people living in the United States and Europe. Dr. Koch’s discovery was the most important step taken toward the control and elimination of this deadly disease.

In 1982, a century after Dr. Koch’s announcement, the first World TB Day was sponsored by the World Health Organization (WHO) and the International Union against Tuberculosis and Lung Disease (IUATLD). The event was intended to educate the public about the devastating health and economic consequences of TB, its effect on developing countries, and its continued tragic impact on global health.

Today, World TB Day is commemorated across the globe with activities as diverse as the locations in which they are held. But more can be done to raise awareness about the effects of TB. Among infectious diseases, TB is now the leading killer of adults in the world, with 1.8 million TB-related deaths in 2015. In the United States, the overall number of TB cases increased over the previous year in 2015 after having declined yearly during 1993–2014.

Until TB is eliminated, World TB Day won’t be a celebration. But it is a valuable opportunity to educate the public about the devastation TB can spread and how it can be stopped.

Epidemiology

Globally, more than 1 in 3 individuals is infected with TB. According to the WHO, there were 8.8 million incident cases of TB worldwide in 2010, with 1.1 million deaths from TB among HIV-negative persons and an additional 0.35 million deaths from HIV-associated TB. In 2009, almost 10 million children were orphaned as a result of parental deaths caused by TB.

Overall, the WHO noted the following:

• The absolute number of TB cases has been falling since 2006 (rather than rising slowly, as indicated in previous global reports)
• TB incidence rates have been falling since 2002 (2 years earlier than previously suggested)
• Estimates of the number of deaths from TB each year have been revised downwards

The 5 countries with the highest number of incident cases in 2010 were India, China, South Africa, Indonesia, and Pakistan. India alone accounted for an estimated 26% of all TB cases worldwide, and China and India together accounted for 38%.

Types of Tuberculosis

Active TB

Active TB is an illness in which the TB bacteria are rapidly multiplying and invading different organs of the body. The typical symptoms of active TB variably include cough, phlegm, chest pain, weakness, weight loss, fever, chills and sweating at night. A person with active pulmonary TB disease may spread TB to others by airborne transmission of infectious particles coughed into the air.

If you are diagnosed with an active TB disease, be prepared to give a careful, detailed history of every person with whom you have had contact. Since the active form may be contagious, these people will need to be tested, as well.

Multi-drug treatment is employed to treat active TB disease. Depending on state or local public health regulations, you may be asked to take your antibiotics under the supervision of your physician or other healthcare professional. This program is called “Directly Observed Therapy” and is designed to prevent abandonment or erratic treatment, which may result in “failure” with continued risk of transmission or acquired resistance of the bacteria to the medications, including the infamous multi-drug resistant TB (MDR-TB).

Miliary TB

Miliary TB is a rare form of active disease that occurs when TB bacteria find their way into the bloodstream. In this form, the bacteria quickly spread all over the body in tiny nodules and affect multiple organs at once. This form of TB can be rapidly fatal.

Types of TB

Cavitary TB

Cavitary TB involves the upper lobes of the lung. The bacteria cause progressive lung destruction by forming cavities, or enlarged air spaces. This type of TB occurs in reactivation disease. The upper lobes of the lung are affected because they are highly oxygenated (an environment in which M. tuberculosis thrives). Cavitary TB can, rarely, occur soon after primary infection.

Symptoms include productive cough, night sweats, fever, weight loss, and weakness. There may be hemoptysis (coughing up blood). Patients with cavitary TB are highly contagious. Occasionally, disease spreads into the pleural space and causes TB empyema (pus in the pleural fluid).

Latent TB Infection

Latent TB occurs when a person has the TB bacteria within their body, but the bacteria are present in very small numbers. They are kept under control by the body’s immune system and do not cause any symptoms.

People with latent TB do not feel sick and are not infectious. They cannot pass the bacteria on to other people. In addition they will usually have a normal chest x-ray and a negative sputum test. It is often only known that someone has latent TB because they have had a test, such as the TB skin test.

Risk factors of Tuberculosis

You are at risk of TB infection if you are around people with active TB disease who are coughing, which releases bacteria into the air. The risk of infection increases for intravenous drug users, healthcare workers, and people who live or work in a homeless shelter, migrant farm camp, prison or jail, or nursing home.

Most people who are infected with the bacteria that cause TB do not develop active disease. The following factors increase the risk that latent disease will develop into active disease:

• Infection with HIV, the virus that causes AIDS and weakens the immune system
• Diabetes mellitus
• Low body weight
• Head or neck cancer, leukemia, or Hodgkin’s disease
• Some medical treatments, including corticosteroids or certain medications used for autoimmune or vasculitic diseases such as rheumatoid arthritis or lupus, which suppress the immune system.
• Silicosis, a respiratory condition caused by inhaling silica dust.

 Causes

The Mycobacterium tuberculosis bacterium causes TB. It is spread through the air when a person with TB (whose lungs are affected) coughs, sneezes, spits, laughs, or talks.

Causes of tuberculosis

TB is contagious, but it is not easy to catch. The chances of catching TB from someone you live or work with are much higher than from a stranger. Most people with active TB who have received appropriate treatment for at least 2 weeks are no longer contagious.

Since antibiotics began to be used to fight TB, some strains have become resistant to drugs. Multidrug-resistant TB (MDR-TB) arises when an antibiotic fails to kill all of the bacteria, with the surviving bacteria developing resistance to that antibiotic and often others at the same time.

MDR-TB is treatable and curable only with the use of very specific anti-TB drugs, which are often limited or not readily available. In 2012, around 450,000 people developed MDR-TB.

Symptoms of Tuberculosis

Although tuberculosis (TB) is most frequently associated with symptoms involving the lungs—because the disease most often affects the lungs—it can affect any organ of the body. The disease can cause a variety of symptoms. If you have symptoms, your doctor will want to know when they began.

People with latent TB infection (an infection without active disease) have no symptoms.

The usual symptoms of TB include:

• Fever
• Chills
• Night sweats
• Cough
• Loss of appetite
• Weight loss
• Blood in the sputum (phlegm)
• Loss of energy

The symptoms may be mild and may not seem particularly worrisome to the patient. In other people, the symptoms become chronic and severe.

Other symptoms of active TB disease depend on where in the body the bacteria are growing. If active TB disease is in the lungs (pulmonary TB), the symptoms may include a bad cough, pain in the chest, and coughing up blood. If active TB is outside the lungs (for example, the kidney, spine, brain, or lymph nodes), it is called extrapulmonary TB and has other symptoms, depending on which organs are affected. For example, tuberculosis in the spine may cause back pain or stiffness.

Diagnosis and test

During the physical exam, your doctor will check your lymph nodes for swelling and use a stethoscope to listen carefully to the sounds your lungs make while you breathe.

The most commonly used diagnostic tool for tuberculosis is a simple skin test, though blood tests are becoming more commonplace. A small amount of a substance called PPD tuberculin is injected just below the skin of your inside forearm. You should feel only a slight needle prick.

Within 48 to 72 hours, a health care professional will check your arm for swelling at the injection site. A hard, raised red bump means you’re likely to have TB infection. The size of the bump determines whether the test results are significant.

If your GP suspects you may have TB, they will send you for testing. If you do have TB, it’s best to know as soon as possible. Delaying treatment makes it more likely you may develop long-term health problems and could put people close to you at risk.

Types of TB test

There are a range of tests to show if you have TB, such as a sputum test, a culture test and x-rays.

Chest x-ray

A chest x-ray can show damage in your lungs, but you might need further tests to prove you have TB, such as sputum and culture tests or scans.

Testing sputum

A lab will use a microscope to look at any sputum (phlegm) that you cough up. If there are TB germs in your sputum, you have tuberculosis of the lungs or throat (pulmonary TB). This test also helps doctors to understand how infectious you may be.

Biopsy

If it is thought that you have TB, but not in your lungs or throat, the doctor may take a biopsy to test for TB. This is a small sample of tissue or fluid taken from the area where the TB is thought to be.

Culture test

This test uses your sputum or tissue sample to grow any TB bacteria that may be there. It tells doctors how infectious you are and also whether your TB is resistant to any antibiotics. This helps ensure they put you on a combination of drugs that will cure you. As TB culture grows slowly, it may take up to eight weeks to get some of the results.

Treatment and medications

Treatment for Active TB

If you have this form of the disease, you’ll need to take a number of antibiotics for 6 to 9 months. These four medications are most commonly used to treat it:

• Ethambutol
• Isoniazid
• Pyrazinamide
• Rifampin

Your doctor may order a test that shows which antibiotics will kill the TB strain. Based on the results, you’ll take three or four medications for 2 months. Afterward, you’ll take two medications for 4 to 7 months.

You’ll probably start to feel better after a few weeks of treatment. But only a doctor can tell you if you’re still contagious. If you’re not, you may be able to go back to your daily routine.

Treatment of latent TB

The treatment of latent TB is considered by many people to be an important part of  TB prevention.

It is not recommended that everyone with latent TB infection (LTBI) should have TB treatment. Rather it is recommended that certain “target” groups should receive treatment. The main “target” groups considered by the World Health Organisation (WHO) to be most at risk from progressing from latent to active TB include people in low TB burden countries:

• Who have had recent contact with an infectious patient;
• With silicosis (there is more about TB & mining);
• Infected with both TB and HIV;
• Who have been or who are in prison;
• Who are immigrants to a low burden country from a high burden country;
• Who are homeless;
• Who are an illicit drug user;
• Who have certain clinical conditions, or conditions which compromise their immune system, such as people with diabetes, and people with chronic renal failure.

In high TB burden countries the populations that are most strongly recommended for the treatment of latent TB infection are people living with HIV, and children under five who are household contacts of pulmonary TB cases.

Treatment for miliary TB

• Antibiotics
• Corticosteroids
• Sometimes surgery

Generally, treatment of miliary tuberculosis is similar to thetreatment of pulmonary tuberculosis.

Antibiotics are given usually given for 6 to 9 months, unless the meninges are affected. Then antibiotics are given for 9 to 12 months.

Corticosteroids may help if the pericardium or meninges are affected.

Tuberculosis bacteria can easily develop resistance to antibiotics, particularly when people do not take the drugs regularly or for as long as they are supposed to.

Surgery is needed for some complications of military tuberculosis.

Prevention of Tuberculosis

If you test positive for latent TB infection, your doctor may advise you to take medications to reduce your risk of developing active tuberculosis. The only type of tuberculosis that is contagious is the active variety, when it affects the lungs. So if you can prevent your latent tuberculosis from becoming active, you won’t transmit tuberculosis to anyone else.

Protect your family and friends

If you have active TB, keep your germs to yourself. It generally takes a few weeks of treatment with TB medications before you’re not contagious anymore. Follow these tips to help keep your friends and family from getting sick:

Stay home. Don’t go to work or school or sleep in a room with other people during the first few weeks of treatment for active tuberculosis.

Ventilate the room. Tuberculosis germs spread more easily in small closed spaces where air doesn’t move. If it’s not too cold outdoors, open the windows and use a fan to blow indoor air outside.

Cover your mouth. Use a tissue to cover your mouth anytime you laugh, sneeze or cough. Put the dirty tissue in a bag, seal it and throw it away.

Wear a mask. Wearing a surgical mask when you’re around other people during the first three weeks of treatment may help lessen the risk of transmission.

Finish your entire course of medication

This is the most important step you can take to protect yourself and others from tuberculosis. When you stop treatment early or skip doses, TB bacteria have a chance to develop mutations that allow them to survive the most potent TB drugs. The resulting drug-resistant strains are much more deadly and difficult to treat.

Vaccinations

In countries where tuberculosis is more common, infants often are vaccinated with bacillus Calmette-Guerin (BCG) vaccine because it can prevent severe tuberculosis in children. The BCG vaccine isn’t recommended for general use in the United States because it isn’t very effective in adults. Dozens of new TB vaccines are in various stages of development and testing.