Is tuberculosis contagious after treatment

Myths about how TB is spread

There are many myths about how TB is spread

In many countries the public is not very well informed, and there are many myths about how TB is passed on. As a result many people believe that TB is hereditary or can be spread through food or water.

In developing countries a major effect of the resulting stigma and discrimination can be the social isolation of patients, both within and outside of the family. Within the family the patient may be forced to eat and sleep separately because of the fear of transmission. Patients may even isolate themselves to avoid infecting others. Education needs to be a major part of TB prevention.

One day I went to visit a family with my sister. While we were there I asked for water. The father gave me a glass of water, but my sister stopped me from drinking it. This confused me and really upset the man. We said nothing about it, but when we left my sister told me that people suspected he had TB, and touching the glass might have given me TB.

There are also myths about how TB can be cured. In 2019 the Chief Minister of Uttarakhand in India, said that living in close proximity to a cow could cure a person of TB,which of course it can’t.1Press Trust of India, “Cows exhale oxygen, can cure Tuberculosis”, 2019,

Tuberculosis Infection: How Does It Spread?

If you find yourself in contact with someone who has tuberculosis (TB), you’ll probably have one big question on your mind: Am I going to get TB?

While TB is easily passed from person to person under certain circumstances, it generally doesn’t spread through casual contact.

How Can You Get TB?

TB is a highly contagious bacterial infection that can quickly spread if not caught, isolated, and treated early. Tuberculosis is an airborne disease, and can be caught by breathing in the air that an infected person has contaminated through:

  • Breathing
  • Coughing
  • Talking
  • Singing
  • Sneezing

TB germs must be forced into the air, and to get a tuberculosis infection you must breathe in those germs. But even if you’ve been around an infected person, or breathed in the bacteria they expelled into the air, you still have a chance at escaping TB — not everyone who breathes in the bacteria will develop tuberculosis.

Ways You Won’t Get TB

If you can get tuberculosis infection by breathing in the air where someone spoke, it should be pretty easy to catch the illness by just touching someone who has TB, right?

Actually, no. You can’t get TB by touching an infected person. Tuberculosis germs don’t stick to clothing or skin; they hang out in the air.

You also can’t get TB by:

  • Giving an infected person a hug or a kiss
  • Using the same toothbrush
  • Eating or drinking after an infected person
  • Shaking hands
  • Sharing clothing, a bed, or towels
  • Using the same toilet as an infected person

Who’s Most Contagious?

A person who has been infected with tuberculosis may not yet show any symptoms of TB, and may have no idea that they’re sick — and they’re also are not contagious at this stage.

If active tuberculosis disease does develop, and symptoms appear — such as persistent coughing, coughing up blood, breathing problems, or flu-like symptoms — the disease is contagious. Even before a TB diagnosis, people can unwittingly transmit tuberculosis to others. People with symptomatic TB are contagious until they have taken their TB medications for at least two weeks. After that point, treatment must continue for months, but the infection is no longer contagious.

Anyone who has been in contact with someone with TB should have a tuberculosis test (also called a PPD test) immediately to find out whether they have the illness, and if they are capable of spreading it to other people.

Who Is Most Susceptible to Tuberculosis?

Being around a person infected with TB, or even breathing in the air contaminated with tuberculosis germs, doesn’t mean that you’ll definitely get TB. However, certain people are more susceptible to the disease than others.

People with healthy immune systems are better able to defend themselves against the progression of tuberculosis infection into active TB disease, while those with weakened immune systems — for instance, people with HIV — are much more susceptible to actually developing active tuberculosis disease.

The longer you spend with someone who has contagious TB, the greater the likelihood that you’ll catch the illness. But even if you are infected with tuberculosis, you may still never get sick. Less than 10 percent of people who have been infected with the tuberculosis bacteria go on to develop active tuberculosis disease.

If you have tuberculosis, it’s very important to take all medications exactly as prescribed and avoid contact with others until you are no longer contagious. And people who are most susceptible to TB should take care to avoid those infected with the disease.

Does TB spread through kissing and sex?

Q: I was successfully treated for tuberculosis (TB) 11 years back. I have developed symptoms again now, in spite of following a healthy lifestyle. My husband’s family (sister, grandmother, father) have suffered from TB (before we were married). Is it possible for a person with latent infection to spread TB through sex/kissing? Is it possible that I could have contracted TB again? I am HIV negative? I have never skipped or forgotten to take the medicine. I took the full course as prescribed by the doctor. Please advise.


Productive cough, fever and weight loss are typical symptoms of pulmonary tuberculosis. Haemoptysis or chest pain, night sweats, fatigue or anorexia are the other systemic manifestations. The sputum may be scanty, or bloody and purulent, and as a result is usually associated with cavitatory lesions in the lung. Pulmonary tuberculosis may manifest in various forms including progressive pulmonary disease, involvement of pleura and reactivated pulmonary disease. Post primary (secondary) tuberculosis is caused either by reactivation of latent infection or by exogenous reinfection. Reactivation of primary lesion occurs more commonly in patients with decreased immunity such as patients receiving transplants, patients infected with human immuno deficiency virus (HIV), and in the elderly patients. Humans are the only source and reservoir for M. tuberculosis infection.

The infectiousness of the source is of primary importance, which determines the possibility of transmission of the disease. This depends on bacillary load of lesions and also on the morphology of the lesion. Lesions with cavities have 100 – 10,000 bacilli, therefore, cases with cavitatory lesions are potentially highly infectious. Cases treated with antitubercular therapy are less infectious than those who are not treated with any antitubercular drugs. The decrease in infectiousness is primarily due to reduction in the bacillary load in the lungs. Environment factors also contribute to transmission of infection. Overcrowding, poor housing, and inadequate ventilation predispose population to development of tuberculosis. Concentration of tubercle bacilli in the environment depends on the exposure to ultraviolet light and ventilation of the surroundings. The infection is transmitted from person to person by inhalation of airborne droplet nuclei. The droplet nucleus is small, measures 5 µm or less and may contain approximately 1 – 10 tubercle bacilli. Theoretically, although single tubercle bacillus may cause disease, upto 10 inhaled bacilli are essential for infection. These droplets by virtue of their small size remain suspended in the air for a very long period of time. Primary infection of lung occurs as a result of inhalation of the infectious aerosols. The risk of infection depends on the exposure to ultraviolet rays and ventilation; therefore, the risk of infection is high in small rooms and in rooms with poor ventilation. There are many risk factors for tuberculosis. HIV is one of the most important risk factors. Case rates for individuals who are infected with both HIV and M. tuberculosis exceed the infective risk of individuals with M. tuberculosis infection who are not infected with HIV. Other factors which increases the risk of tuberculosis are steroid therapy, cancer chemotherapy, malignancies and under nutrition. The later condition alters cell-mediated immunity therefore, is responsible for the increased frequency of tuberculosis in impoverished persons.

Tuberculosis: Will it spread if we kiss?

Tuberculosis may be transmitted during the act of kissing if the person kissing is an open case of tuberculosis excreting large numbers of mycobacteria in the sputum. Transmission through sex is a possibility, but is rare. You are advised to consult your Physician for rechecking your health status and reviewing your antitubercular regimen, because drug resistance in the mycobacteria is a notorious problem encountered frequently nowadays. Please get your blood screened for HIV antibodies by ELISA.

Patients taking TB treatment may be potentially infectious for longer than previously thought

Patients taking directly observed therapy (DOTS) for tuberculosis (TB) may be potentially infectious for longer than previously thought, investigators report in the August 15th edition of Clinical Infectious Diseases. Moreover, the researchers found that many patients were TB culture-positive despite being smear-negative.

Although prolonged smear and/or culture positivity during treatment was associated with the presence of drug-resistant TB, the majority of patients with drug-sensitive TB also took longer than two weeks to test culture-negative, and 10% of patients with drug-sensitive TB were still culture-positive at least 2 months after starting treatment.

It has long been thought that patients with drug-susceptible TB are non-infectious after two weeks of therapy for the infection.



In a bacteria culture test, a sample of urine, blood, sputum or another substance is taken from the patient. The cells are put in a specific environment in a laboratory to encourage cell growth and to allow the specific type of bacteria to be identified. Culture can be used to identify the TB bacteria, but is a more complex, slow and expensive method than others.

multidrug-resistant tuberculosis (MDR-TB)

A specific form of drug-resistant TB, due to bacilli resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs. MDR-TB usually occurs when treatment is interrupted, thus allowing organisms in which mutations for drug resistance have occurred to proliferate.


Mucus and other matter that is brought up from the lungs by coughing.

drug resistance

A drug-resistant HIV strain is one which is less susceptible to the effects of one or more anti-HIV drugs because of an accumulation of HIV mutations in its genotype. Resistance can be the result of a poor adherence to treatment or of transmission of an already resistant virus.

directly observed therapy (DOT)

When a health care professional watches as a person takes each dose of a medication, to verify that all doses are taken as prescribed.

“The data presented here question the notion that patients with TB who are culture positive at baseline are non-infectious after 2 weeks of treatment or a negative smear”, write the investigators, “most patients are both smear and culture positive at 2 weeks, and significant proportions remain positive for months.”

The study was conducted in Lima, Peru, and involved 93 patients with both culture and smear-positive TB who were provided with DOTS.

In the six months following the initiation of TB therapy the patients provided sputum samples. These were analysed to see if sputum which were smear-negative were also culture-negative; how long it took for TB to become both smear and culture-negative; and to see if the presence of drug resistance was associated with delays in becoming non-infectious.

Patients became smear-negative a median of 18 days after starting TB therapy, and culture-negative after a median of 41 days.

However, it took a median of 48 days for 90% of patients to become smear-negative, and median of 93 days for 90% to attain culture-negativity.

The presence of multidrug-resistant tuberculosis (MDR-TB) was associated with a longer time to both smear and culture negativity.

Ninety percent of patients with drug-sensitive TB were culture negative after 60 days, but it took a median of 124 days for patients with MDR-TB to achieve this outcome.

In statistical analysis, MDR-TB was shown to be a significant predictor of delayed time to attaining negative cultures (p = 0.007).

At treatment initiation, 67% of patients with culture-positive MDR-TB were also smear positive. After 120 days of treatment, 80% of patients with culture-positive samples were MDR-TB smear-negative.

Among patients with drug-sensitive TB, the median time to culture-negativity was 36.5 days

“This study demonstrates that patients with TB who have fully susceptible disease remain sputum culture positive for much longer than is conventionally believed”, comment the investigators.

They add, “conversion from smear or culture positivity to negativity is significantly delayed by both MDR and resistance that is not MDR”.

Under most DOTS treatment regimens, patients “step-down” from therapy consisting of four drugs to a combination of two drugs after 60 days if smear-negative. The investigators comment, “our data indicate frequent persistent culture positivity among smear-negative patients at this time point; this may partly explain high rates of apparent recurrence of MDR among patients considered ‘cured’ by smear diagnosis.”

The researchers conclude, “long-term smear-negative shedding and drug resistance must be considered jointly if TB transmission is to be controlled.”

The author of an accompanying editorial suggests that the study illustrates “the need for new research efforts to evaluate and challenge our old TB control paradigms. During the past 10 years, TB has changed the rules of the game, whereas our policies have stayed the same wishful thinking. New public health policies based on scientific evidence are urgently needed to combat the growing scourge of drug-resistant TB.”

What is TB? How is it treated?

Ask the expert
Reviewed January 2018

Q: What is TB? How does it spread? How is it treated?

A: Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis) that most often affect the lungs. Tuberculosis is curable and preventable.

TB is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air. A person needs to inhale only a few of these germs to become infected.

About one-third of the world’s population has latent TB, which means people have been infected by TB bacteria but are not (yet) ill with disease and cannot transmit the disease.

People infected with TB bacteria have a lifetime risk of falling ill with TB of 10%. However persons with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco, have a much higher risk of falling ill.

When a person develops active TB (disease), the symptoms (cough, fever, night sweats, weight loss etc.) may be mild for many months. This can lead to delays in seeking care, and results in transmission of the bacteria to others. People ill with TB can infect up to 10-15 other people through close contact over the course of a year. Without proper treatment up to two thirds of people ill with TB will die.

Since 2000, 53 million lives have been saved through effective diagnosis and treatment. Active, drug-sensitive TB disease is treated with a standard 6-month course of 4 antimicrobial drugs that are provided with information, supervision and support to the patient by a health worker or trained volunteer. The vast majority of TB cases can be cured when medicines are provided and taken properly.


Individuals who are exposed to TB often do not feel sick or present any symptoms. These individuals are not contagious at this point, unless their infection persists into active TB disease. At this point the bacterium can be spread through microscopic droplets as the patient sneezes, coughs, talks, or otherwise projects contaminated sputum/saliva from their body. People nearby may breathe in these bacteria and become infected as the bacteria can stay in the air for several hours.

As a top infectious disease, current estimates are that TB infects nearly two billion people or about one-third of the world population. These infected, non-disease active people are considered latent TB cases. This means that people are infected with TB bacteria, but are not yet ill or active cases. Infected people have a lifetime risk of 10 percent to falling ill to TB.

According to the World Health Organization, in 2014 9.6 million people had developed active TB illness and 1.5 million died from the disease. During 2014, the CDC reported that 9,421 active TB cases were recorded within the United States. There were 108 cases of TB disease in Indiana in 2014.

Exposure to TB

What to Do If You Have Been Exposed To TB

You may have been exposed to TB bacteria if you spent time near someone with TB disease. The TB bacteria are put into the air when a person with active TB disease of the lungs or throat coughs, sneezes, speaks, or sings. You cannot get TB from

  • Clothes
  • Drinking glass
  • Eating utensils
  • Handshake
  • Toilet
  • Other surfaces

If you think you have been exposed to someone with TB disease, you should contact your doctor or local health department about getting a TB skin test or a special TB blood test. Be sure to tell the doctor or nurse when you spent time with the person who has TB disease.

It is important to know that a person who is exposed to TB bacteria is not able to spread the bacteria to other people right away. Only persons with active TB disease can spread TB bacteria to others. Before you would be able to spread TB to others, you would have to breathe in TB bacteria and become infected. Then the active bacteria would have to multiply in your body and cause active TB disease. At this point, you could possibly spread TB bacteria to others. People with TB disease are most likely to spread the bacteria to people they spend time with every day, such as family members, friends, coworkers, or schoolmates.

Some people develop TB disease soon (within weeks) after becoming infected, before their immune system can fight the TB bacteria. Other people may get sick years later, when their immune system becomes weak for another reason. Many people with TB infection never develop TB disease.

Learn about TB Prevention.

Related Links

For Patients

For Health Care Providers

  • Infection Control and Prevention Guidelines
  • Infection Control and Prevention Fact Sheets

TB infection vs. TB disease

There is a difference between TB infection and TB disease. When a person has been exposed to someone with TB disease and has breathed in the TB germs, that person may become infected with TB. In most cases, people with healthy immune systems can contain the infection at that point and not become ill with TB disease. A person with TB infection only (positive TB skin test but normal chest x-ray) is not sick and is not contagious to others. TB medicine can help kill the bacteria and prevent the development of TB disease in the future.

However, if a person with TB infection does not take preventive medicine, the bacteria may grow and cause active TB disease. TB symptoms may include a constant cough that lasts two or more weeks, chest pain, weakness, and loss of appetite. When a person has active TB disease, the individual may be contagious and cause infection in other people, particularly those with whom they spend the most time.

Someone with active TB disease will need to take several TB medicines for many months in order to become well and not infect others. However, they may no longer be infectious after a few weeks of medicine and would be able, once cleared by the Health Department, to return to work and normal activities while they are completing their TB treatment. People can have active TB in any organ of the body, but it is only infectious to others when it is in the lungs or larynx.

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