Tuberculosis (TB) is a bacterial infection caused by a germ called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but they can also damage other parts of the body. TB spreads through the air when a person with TB of the lungs or throat coughs, sneezes or talks. If you have been exposed, you should go to your doctor for tests. You are more likely to get TB if you have a weak immune system. Symptoms of TB in the lungs may include • A bad cough that lasts 3 weeks or longer • Weight loss • Coughing up blood or mucus • Weakness or fatigue • Fever and chills • Night sweats
If not treated properly, TB can be deadly. You can usually cure active TB by taking several medicines for a long period of time. People with latent TB can take medicine so that they do not develop active TB.
INTRODUCTION
Tuberculosis, or TB, is a bacterial infection that causes more deaths in the world than any other infectious disease. About 2 billion people are infected with tuberculosis worldwide. When tuberculosis becomes active, it kills 60% of those who are not treated. This amounts to 3 million deaths worldwide every year. There is a treatment for tuberculosis. When treated, 90% of patients who have an active tuberculosis infection survive. This patient education program explains latent and active tuberculosis infections. The program discusses the diagnosis, treatment, and prevention of tuberculosis.
CAUSES
Tuberculosis is an infection caused by a bacterium called Mycobacterium tuberculosis. The bacterium is also called tubercle bacillus. Tuberculosis spreads from person to person through air as a person with active tuberculosis coughs, sneezes, or expels air. After a person becomes infected, the tuberculosis bacteria are controlled by the person’s immune system. The infection becomes latent, or confined. When the bacteria spread out of control, the infection becomes active. Since most infected people breathe out only a few bacilli when they exhale, transmission of tuberculosis usually only occurs after one or more months of exposure to someone with active tuberculosis. Adequate ventilation is the most important measure to prevent the transmission of tuberculosis. Tuberculosis is not usually transmitted through personal items belonging to those with tuberculosis, such as clothing, bedding, or other items they have touched.
LATENT VS. ACTIVE INFECTION
As a person breathes infected air, the bacilli go to the lungs through the bronchioles. At the end of the bronchioles are alveoli. Alveoli are balloon-like sacs where the blood takes oxygen from inhaled air and releases carbon dioxide into the air exhaled. Tuberculosis bacilli infect the alveoli. The body’s immune system fights them. The immune system includes special blood cells that identify and destroy foreign material, including viruses and bacteria. These blood cells are called white blood cells. Special white blood cells called macrophages attack tuberculosis bacteria. Many of the bacteria die. Tuberculosis bacteria have a cell wall made of a complex waxy material. This wall protects some bacteria inside the macrophage! Special cells of the immune system surround and separate the infected macrophages. The mass resulting from the separated, infected macrophages are hard, grayish nodules called tubercles. If an infected person is not healthy, particularly if he or she has a weak immune system, the bacilli may overwhelm the immune system. The bacilli could of the tubercles in the alveoli and spread to the lungs and other sites of the body through the bloodstream. This is called active tuberculosis. If an infected person is healthy, the initial tuberculosis infection is controlled by the immune system. The tuberculosis bacilli may remain confined within the tubercles for years. This is called latent tuberculosis. Latent means dormant or sleeping. About 90% of infected people heal completely after the initial infection. The tubercles calcify and the bacteria cannot break again. For about 10% of infected people, the bacilli inside the tubercles become active sometime later in life when their immune system becomes weak. This is known as active tuberculosis.
SYMPTOMS
Active tuberculosis spreads from alveoli through the bloodstream or lymphatic system. It may invade other areas in the body, such as the skin, kidneys, bones, reproductive system, or urinary system. At the new sites, the body's immune system kills many bacilli, but immune cells and local tissue die as well. The dead cells form masses called granulomas, where bacilli can survive but not grow. The early symptoms of active tuberculosis include: • weight loss • fever • night sweats • loss of appetite Some patients may have little or no symptoms with TB. As more lung tissue is destroyed and granulomas expand, cavities develop in the lungs, and sometimes expand into larger lung airways. This allows large numbers of bacilli to spread when the patient coughs. As granulomas grow in the lungs, they may cause more coughing and shortness of breath as they destroy lung tissue. Granulomas can also eat away at blood vessels, causing bleeding in the lungs, which could result in bloody sputum. Symptoms of tuberculosis involving areas other than the lungs vary, depending on the organ affected. For example, when tuberculosis infects the spine, it can cause severe back pain or back deformities.
DIAGNOSIS
Latent tuberculosis or initial infection can be diagnosed with a skin test called a Mantoux test. This test can identify most people infected with tubercle bacilli 6-8 weeks after initial exposure. A substance called PPD is injected under the skin of the forearm and examined 48-72 hours later. If a red welt forms around the injection site, the person may be infected with M. tuberculosis, but the disease is not necessarily active. A blood test known as QuantiFERON® -TB can also show if a patient has been exposed or is infected with M.tuberculosis To diagnose active tuberculosis, a doctor relies on symptoms, the patient’s history of exposure to TB, and x-rays that may show evidence of TB infection, usually in the form of cavities or lesions in the lungs. The doctor will also take sputum and other samples to be examined by a pathologist. It is important to determine the type of tuberculosis bacteria involved in order to prescribe the most effective medication.
TREATMENT
If not treated, active tuberculosis can be fatal, killing up to 60% of patients. When treated, a cure can be achieved in 90% of all cases. Successful treatment of tuberculosis depends on cooperation between the patient and doctor. Patient education is essential, and many doctors prefer to hospitalize the patient in order to observe him or her during treatment. This treatment consists of taking more than one medication for a duration of months! The following are some of the medications used to treat tuberculosis: • Isoniazid • Rifampin • Ethambutol • Pyrazinamide Some of these medications may have very serious side effects and some should not be combined with other medications or with alcohol. This is why it is very important to take them under your doctor’s supervision and follow his or her recommendations and suggestions. People who have been treated for at least two weeks are usually not contagious anymore. Patients who do not take their medications as often and as long as prescribed, give the bacteria a chance to become resistant to the treatment. This is why it is VERY important to follow doctor’s instructions.
PREVENTION
As with most infectious disease, it is better to prevent the disease than to treat it. Tuberculosis is very preventable. If infected people cover their mouth and nose when coughing or sneezing, the spread of TB can also be prevented. Identifying infected people early and treating them with medications is one of the most effective ways to prevent TB from spreading. The drug INH®can prevent TB and should be given to people who • have latent tuberculosis • are in close contact with infected patients • have been in countries where tuberculosis is common • are at risk of getting infected with tuberculosis
VACCINES The tuberculosis vaccine is called BCG. BCG prevents the spread of M. tuberculosis within the body, but does not prevent initial infection. It is recommended for infants in parts of the world where TB is common The vaccine BCG is not recommended for general use in some countries.
SUMMARY
Tuberculosis is a bacterial infection that can be fatal. The body’s immune system can usually fight the infection and confine it successfully. When the immune system is weak, confined tuberculosis bacteria can become active and spread to other parts of the body. This is active tuberculosis. Thanks to advances in medicine, treatment is available to treat active TB. It is very important for the patient to follow the prescribed treatment. Tuberculosis can be prevented through good hygiene, including good ventilation and covering the mouth when coughing. A vaccine is available for some infants and is recommended for those who live in parts of the world with high occurrence of tuberculosis.
