DEFINITION
Tuberculosis is an infectious disease that usually affects the lungs. Compared with other diseases caused by a single infectious agent, tuberculosis is the second biggest killer, globally.
In 2015, 1.8 million people died from the disease, with 10.4 million falling ill.
In the 18th and 19th centuries, a tuberculosis epidemic rampaged throughout Europe and North America, before the German microbiologist Robert Koch discovered the microbial causes of tuberculosis in 1882.
Following Koch's discovery, the development of vaccines and effective drug treatment led to the belief that the disease was almost defeated. Indeed, at one point, the United Nations, predicted that tuberculosis (TB) would be eliminated worldwide by 2025.
However, in the mid-1980s, TB cases began to rise worldwide, so much so, that in 1993, the World Health Organization (WHO) declared that TB was a global emergency; the first time that a disease had been labeled as such.
Doctors make a distinction between two kinds of tuberculosis infection: latent and active.
Latent TB - the bacteria remain in the body in an inactive state. They cause no symptoms and are not contagious, but they can become active.
Active TB - the bacteria do cause symptoms and can be transmitted to others.
About one-third of the world's population is believed to have latent TB. There is a 10 percent chance of latent TB becoming active, but this risk is much higher in people who have compromised immune systems, i.e., people living with HIVor malnutrition, or people who smoke.
TB affects all age groups and all parts of the world. However, the disease mostly affects young adults and people living in developing countries. In 2012, 80 percent of reported TB cases occurred in just 22 countries.
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.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.
Early warning signs
According to the Centers for Disease Control and Prevention (CDC), the symptoms of TB disease include:
• feeling sick or weak
• loss of appetite and weight loss
• chills, fever, and night sweats
• a severe cough that lasts for 3 weeks or more
• chest pain
TB can also affect other parts of the body. Symptoms will depend on the part it affects.
Symptoms
During a latent stage, TB has no symptoms. When TB is active TB, the cough, fever, and other symptoms can appear.
While TB usually affects the lungs, it can also affect other parts of the body, and the symptoms will vary accordingly.
Without treatment, TB can spread to other parts of the body through the bloodstream:
• The bones: There may be spinal pain and joint destruction.
• The brain: It can lead to meningitis.
• The liver and kidneys: It can impair the waste filtration functions and lead to blood in the urine.
• The heart: It can impair the heart's ability to pump blood, resulting in cardiac tamponade, a condition that can be fatal.
Risk factors
People with compromised immune systems are most at risk of developing active tuberculosis. For instance, HIV suppresses the immune system, making it harder for the body to control TB bacteria. People who are infected with both HIV and TB are around 20-30 percent more likely to develop active TB than those who do not have HIV.Tobacco use has also been found to increase the risk of developing active TB. About 8 percent of TB cases worldwide are related to smoking.
People with the following conditions have an increased risk:
• diabetes
• certain cancers
• malnutrition
• kidney disease
Also, people who are undergoing cancer therapy, anyone who is very young or old, and people who abuse drugs are more at risk.
Travel to certain countries where TB is more common increases the level of risk, too.
Countries with higher tuberculosis rates
The following countries have the highest TB rates, globally:
• Africa - particularly West African and sub-Saharan Africa
• Afghanistan
• Southeast Asia: including Pakistan, India, Bangladesh, and Indonesia
• China
• Russia
• South America
• Western Pacific region - including the Philippines, Cambodia, and Vietnam
Prevention
A few general measures can be taken to prevent the spread of active TB.
Avoiding other people by not going to school or work, or sleeping in the same room as someone, will help to minimize the risk of germs from reaching anyone else.
Wearing a mask, covering the mouth, and ventilating rooms can also limit the spread of bacteria.
TB vaccination
In some countries, BCG injections are given to children to vaccinate them against tuberculosis. It is not recommended for general use in the U.S. because it is not effective in adults, and it can adversely influence the results of skin testing diagnoses.
The most important thing to do is to finish entire courses of medication when they are prescribed. MDR-TB bacteria are far deadlier than regular TB bacteria. Some cases of MDR-TB require extensive courses of chemotherapy, which can be expensive and cause severe adverse drug reactions in patients.