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How is TB spread? – Tuberculosis

How is TB spread? Tuberculosis (TB) is an infectious disease caused by a bacterium, which transmits through droplets from the respiratory system.

In this article, there will be a discussion on what this disease is and how TB is spread. Then there will be a thorough explanation of other aspects of tuberculosis, such as its symptoms, how the disease works, and how it is treated and diagnosed. For further information directly from a doctor, continue reading this article.

What is tuberculosis?

Tuberculosis (TB) is an infectious diseaseMycobacterium tuberculosis is the bacterium that causes TB infection. This disease is the first cause of infectious-related mortality. This means that tuberculosis is the infection that causes most deaths worldwide.

Tuberculosis (Mycobacterium tuberculosis bacillus)
Source

In the US and other industrialized countries, new TB infections are decreasing. This is an ancient disease, as there are records down to 10.000 years ago. Scientists determined this by bone-specific characteristics of skeletal TB found in Europe in ancient skeletons. Therefore, we can expect tuberculosis to stick around, although this could change with the help of modern medicine.

TB can present with a wide variety of symptoms depending on the site of infection. This is because TB bacterium can affect different body locations. Disease transmission occurs only from human to human through respiratory fluids. This means that in order to get the infection, a person needs close contact with a sick patient.

Because of respiratory transmission, the lungs are the most common site of infection. In this case, the disease receives the name of pulmonary tuberculosis. The most common symptoms are persistent cough, fever, weight loss, and night sweats.   

The primary lung infection can spread to other sites like the brain, the bones, or the lymph nodes. Check the sections below for more information on different tuberculosis presentations. 

Although it has a simple transmission mode, approximately only 5% of those infected develop an active infection. In other words, only 5 % of those infected will develop symptoms and will require treatment. The rest will not experience any symptoms and will progress into a latent TB infection. There is more information below on active and latent tuberculosis. 

How is TB spread?

Many wonder how TB is spread as this disease can affect different organs. Since the bacterium lives mainly in the lungs, it comes out in little respiratory droplets.

One person can produce up to 3000 droplets in just one cough, and each droplet can infect a different person.

The smallest droplets lose water rapidly in the air and become very light. This allows them to float for more time. A person acquires the infection when they breathe in droplets with the bacterium, which reaches the lungs.  

In this sense, you can not get infected by shaking hands, sharing cups or utensils, or sitting in the bed of a TB patient. However, it is very important to consider that patients with active TB should wear a surgical face mask. This is in order to prevent the spread of droplets that can be contagious. Tuberculosis transmission is more common between people that share a household or sleep together. Exposed groups also include friends, family, coworkers, and anyone in contact with an active patient without a face mask. 

In about 8-9 people out of 10, the disease presents in the lungs. Still, other sites of infection can appear as a result of this first pulmonary infection. When the disease appears outside of the lungs, it becomes an “extrapulmonary infection.” Extrapulmonary tuberculosis is rarely contagious. 

What is the difference between TB infection and TB disease?

A tuberculosis infection means that a person has Mycobacterium tuberculosis. Nevertheless, not all infections cause disease. A healthy person can live with a latent tuberculosis infection without even realizing it. In fact, around 95% of people with tuberculosis have latent infections, and most of them don’t know it.   

Latent infections are usually nonproblematic in people with normally functioning immune systems. An immune system is a group of cells all over the body in charge of fighting infections. The immune system is the one that controls the TB bacterium to produce the latent infection. Restricted to a small area of the lungs without affecting its normal function. Most importantly, patients with latent TB cannot pass on the disease.  

On the other hand, patients with immune system problems may develop active TB disease. Such conditions include patients with untreated HIV infection, patients with organ transplants, lupus, or cancer patients. They can contract the infection in a moment and develop the immune system condition in the course of their lifetime. When tuberculosis-infected patients start experiencing symptoms, it becomes TB disease. 

In general, people with latent TB do not feel sick and don’t have any symptoms. They can not spread the disease, but they are at risk of developing it at some point in their life. In contrast, people with TB disease feel sick and have one or more symptoms. Besides, they might be able to spread the disease. 

Who is at risk of tuberculosis?

It is important to differentiate the risk of having TB infection and TB disease to talk about this. 

Those at a higher risk of infection still have a higher chance of developing latent TB. This group includes: 

  • Those who know and are in contact with someone with active tuberculosis
  • Travelers to areas where tuberculosis is common, especially those that stay for longer periods. 
  • Healthcare workers in contact with patients at risk. 
  • Children and teenagers in contact with adults at high risk. 
  • Populations like incarcerated people, low-income populations, and people who abuse alcohol or other drugs.  

On the other hand, those at risk of developing TB disease are: (remember that in order to get the disease, a patient must first get the infection) 

  • People that are living with HIV and without treatment. 
  • Children under 5 years. 
  • Patients on medication that make the immune system weaker. This includes patients with rheumatoid arthritis, lupus, a transplanted organ, and different types of cancer. 
  • People with a recent TB infection. Although it is more likely to develop latent TB, healthy recently infected patients can develop active TB. The risk is highest the first two years after the infection. 
  • Patients with a history of tuberculosis disease, especially those who remained untreated. 
  • People with silicosis, diabetes, chronic kidney disease
  • People who undergo surgeries to produce weight loss. 
  • Malnourished people. 
  • Cigarette smokers, alcohol, and other drug abusers. 
  • Low-income populations. 

What are the symptoms of tuberculosis?

The most common, pulmonary tuberculosis, has its main symptom: cough. Especially any cough that lasts for more than three weeks. Shorter-lasting coughs are usually because of a virus or other bacteria. Besides coughing, patients will also experience: chest pain, coughing up sputum, fever, and weight loss.

Coughing up sputum means that mucus comes up when coughing. Mucus (phlegm) comes from the deep parts of the lung. In some cases, the bacteria and the body response may break up the lung tissue. This situation causes bloody phlegm. Doctors call this “hemoptysis.” 

Fever commonly appears during the afternoon or at night. Some people experience chills before a fever peak. After the fever peak, patients refer to experiencing profuse sweating. This is very common of tuberculosis patients. 

Weight loss is usually due to a loss of appetite, but some patients may lose weight either way.

File:Depiction of a tuberculosis patient.png
Depiction of a tuberculosis patient
Source

Symptoms vary in older adults where fever may not be common, and the disease can resemble other bacterial pulmonary infections. In contrast, children have a higher chance of experiencing an extrapulmonary disease. This means that symptoms will depend on the site of infection. 

What are common extrapulmonary locations? 

Besides the lungs, the most common sites of infection are the lymph nodes, the brain, the bones, the adrenal glands, and the gut.

The TB bacterium enters the body in the same way: through the lung. Extrapulmonary infections occur when the immune system is unable to contain the infection in the lung. Most patients with this kind of infection have a weak immune system.   

Lymph nodes are all over the body. They are small bags filled with cells from the immune system. In some common infections like strep throat, lymph nodes from the neck become enlarged. People call these “swollen glands.” They become swollen because the immune system is fighting the infection.

Lymph node tuberculosis is called “miliary TB.” It can affect lymph nodes all over the body, but neck lymph nodes are the most common. Usually, just one lymph node becomes enlarged, hard at the touch, and painless.   

When tuberculosis affects the brain, it affects specifically its protection layers. These layers are the meninges. The name of the disease is tuberculous meningitis. It is common in small children. Symptoms are very similar to those of bacterial meningitis: fever, vomiting, loss of appetite, confusion, and dislike for bright lights. Tuberculous meningitis leaves important side effects on kids. 

The main affected bone is the spine. This is the long succession of bones in our back. The bones are called vertebrae. Skeletal tuberculosis usually affects one vertebra. In this case, it receives the name of Pott’s disease. Back pain is the most common symptom. Also, about half of the patients refer to having paralysis of the lower limbs. 

Other locations offer multiple symptoms. Consult a health practitioner for more information. 

How do you diagnose tuberculosis?

There are different tests to diagnose tuberculosis. Some are useful for tuberculosis infection, and others may help diagnose the disease. There are two main tests to identify whether a person has a TB infection or not. These are the Mantoux Tuberculin Skin Test (TST) and Interferon-gamma release assay (IGRA).

In the TST, a healthcare provider injects a small amount of a liquid that contains portions of the tuberculosis bacterium. If the body has the bacteria (latent infection), it will recognize and react to the liquid (called PPD). The reaction is a skin bump that appears after 48 h. At this moment, a doctor or nurse will measure the bump to interpret the results. Interpretation depends on the risk factors and other conditions. Ask a physician or nurse about the many possibilities of the results. 

The IGRA also relies on the ability of the body to recognize the TB bacterium in a latent infection. In this TB blood test, a nurse or lab technician draws blood from a vein of the patient’s forearm. In the lab, a technician mixes the blood sample with a liquid similar to the one from the TST. After this, they measure the reaction in the blood. This test is more reliable in patients who have received the tuberculosis vaccine.  

The two main methods to diagnose tuberculosis disease are acid-fast bacilli (AFB) smear and culture. In the AFB smear, a lab technician will analyze a sputum sample (phlegm) from the patient, looking for TB germ. This technique is reliable, but many patients have a negative AFB smear, and they do have the disease. Cultures take a sample of sputum and put it in a substance where bacteria can continue growing. If the bacterium appears, the culture confirms the disease. Culture results take 4 weeks to come out.

File:Dense opacity of primary pulmonary tuberculosis.jpg
Dense opacity of primary pulmonary tuberculosis
Source

Which is the treatment for tuberculosis?

The TB treatment varies depending on if the patient has an active disease or a latent one. It will also depend on which site the TB bacillus is affecting the infected person.

The typical TB medicine used for active pulmonary TB is isoniazid, rifampin, ethambutol, pyrazinamide. The treatment for this disease goes from a 6 to 9-month period, reliant on the doctor’s consideration. In total, there’re 10 drugs approved by the FDA to treat TB disease, but these four are the first line.

People who have latent TB can also get treatment to reduce the risk of evolving to active disease. The treatment consists of 3 drugs which are isoniazid, rifampin, rifapentine. Doctors use these drugs in different ways and combinations. For example, the treatment can be 3 months long using isoniazid and rifapentine once a week for a total of 12 doses. On the other hand, it can be 6 to 9 months long using isoniazid only every day or twice weekly. Mostly, this treatment scheme depends on the drug’s availability and the convenience of the patient to complete it. 

Now, if millions of people have latent disease, why does not everyone get treatment for it? The people who should get this preventive therapy are those who are more at risk of developing the disease. People with HIV who are organ transplant recipients or have evidential damage of the lung should receive these antibiotics. 

For people with HIV, doctors prescribe the same medications along with the therapy against HIV. In some cases, there can be drug interactions between TB treatment and HIV treatment. For that, doctors change the treatment scheme to another more suitable for the patient’s particular case.

What are the complications of TB?

Tuberculosis can be a very dangerous disease for some people, in which can even lead to death. An untreated TB can allow for the bacteria to disseminate throughout the body and infect other places. It can also cause serious pulmonary issues that can affect a patient’s life permanently.

One dangerous place the tuberculosis bacteria can spread to is the meninges. These are various layers of different types of tissue that surround and protect the central nervous system (brain and spine). When the meninges result infected (TB meningitis), it directly affects the brain and its normal functioning. This type of infection is more dangerous as it compromises the brain. It can be harder to treat varying on its extend.

There can be some complications of the disease that happen while the disease itself develops. One of them is sepsis. This is an exaggerated response from the body to the bacteria, to the point where it can cause death. In sepsis, the body’s immunological system acts in a harmful way, leading to organ failure and damage of their tissues.  

After an infectious TB disease occurs in the lungs, there can be consequences in its tissue. The tuberculosis bacteria create “caverns” in the lungs, that even after a doctor treats the disease, they remain. Afterward, other bacteria and fungus can infect those susceptible places in the lungs and generate new problems for the patient. Even if patients don’t develop other infectious diseases, they can have respiratory problems that accompany them for their whole life.

What can be done to prevent the spread of tuberculosis?

The spread of tuberculosis can be prevented by resolving the risk factors we previously mentioned. For example, people should not live in overcrowded households with poor ventilation, especially in countries where TB is common. This also includes jails, as a lot of them are overcrowded and unventilated.

People who have active TB should be isolated, and people who are in contact with them should use masks. An example of this is healthcare professionals in constant contact with these patients in areas where the disease is common. 

There is a vaccine that is given to prevent the severe forms of the disease, which can get complicated. Usually, children receive them as they are older it doesn’t work as well. Healthcare professionals should get the vaccine even though they are not children as they are at more risk.

Do you have symptoms of TB?

This tool is a Tuberculosis Symptoms Checker. It gathers the most important signs, symptoms, and risk factors for the infection. Therefore, the tool would tell anybody who uses it the likelihood of their symptoms because of tuberculosis. Using the tool is free and would only take a few minutes.

What do you think?

Written by Dr. Esteban Kosak

Doctor of Medicine - MD Recently Graduated from Medical School and inspired to aid the global population during this situation. I think that we shall no longer be waiting to see a doctor when we feel sick. Several times we feel disease searches in Google drive us to a rabbit hole and come out thinking that we may die of cancer or something very serious, given that symptoms may seem to fit a wide variety of illnesses. Since I recently graduated from medical school. I have all the medical information fresh in my mind. My thorough experience as an expert researcher allows me to very-well known the different diseases and conditions that affect human bodies. Empowered by the United Nations 17 Sustainable Development Goals (SGDs). I think that we all can provide a grain of sand to help humanity. That's why we created Symptoms.Care a place where you can come and screen your symptoms and find what different illnesses can be related to them. Armed with the right information you can instantly, discretely, secure and from the comfort of your home talk with a Doctor that can Evaluate your Symptoms and help you seek the right treatment.

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