This post is the fifth and final in a series on Drug Resistant Superbugs.

Yesterday, 24 March 2014, was World Tuberculosis Day. For most people in the developed world, tuberculosis (TB) is a thing of the past. But for many people around the world, TB remains a very real threat.

Every year, three million people with TB are untreated around the world. Together with HIV/AIDS, TB is the leading cause of death from an infectious disease. Globally, 1.3 million people die from TB every year.

The medications that successfully treat TB are causing a new wave of drug resistance. Resistant strains of TB are on the rise, accounting for 630,000 cases worldwide. Some strains are multidrug-resistant (MDR-TB) and others are extensively drug-resistant (XDR-TB). These two types of resistant strains can spread and infect other people.

The spread of XDR-TB is leading to an untreatable type of tuberculosis, which is worrying for persons with HIV or other conditions that weaken the immune system. A major difficulty in managing drug resistance is the delay between suspecting TB and confirming it. A better understanding of TB resistance and a global effort to find and treat infected people is essential to stopping the spread of the disease.

What is TB?                                                   

TB is an infectious disease caused by bacteria called Mycobacterium tuberculosis. The bacteria usually attack the lungs; although other organs, such as kidney, spine and brain can be affected. If left untreated, TB can be fatal. TB bacteria is only spread through air droplets. When a person with active TB coughs or sneezes, people nearby can inhale the bacteria and become infected.

Latent and active tuberculosis

Not all people who inhale TB bacteria develop active TB disease. The body’s immune system can stop the bacteria from reproducing thus making the infection latent or inactive. People with latent TB do not feel sick; they have no symptoms and a normal chest x-ray. However, they usually have a positive skin or blood test result. People with latent TB cannot spread TB to others. Latent TB can later progress to active TB unless treatment is given.

Only people with active pulmonary TB disease can spread the bacteria to others. Most cases of active TB result from untreated latent TB. A person with active TB has a positive skin or blood test, an abnormal chest x-ray and a positive sputum smear that shows TB bacteria. Active TB has symptoms that may include:

•       A bad cough that last three weeks or longer.
•       Pain in chest.
•       Coughing up blood or sputum.
•       Fever and chills.
•       Swollen glands
•       No appetite and weight loss.
•       Night sweats.
•       Weakness or fatigue.

Treatment

Treating latent TB decreases the risk of developing active TB disease. It also helps eliminate the spread of the disease. Latent TB has fewer bacteria than active TB, making the treatment easier and faster. A common treatment for latent TB is isoniazid antibiotic for 6 to 12 months.

Active TB is treated with a combination of medications (rifampin, ethambutol and pyrzinamide) along with isoniazid. The treatment usually lasts many months or years. Successful treatment is largely dependent on patient compliance.

What causes drug-resistant tuberculosis

Countries with higher poverty rates tend to have a heavier burden of drug-resistant strains. TB drug-resistance occurs more often when people:

•       Are in close contact with others known to have drug-resistant TB disease.
•       Live in areas where drug-resistant TB is high.
•       Don’t complete the entire antibiotic regime.
•       Take the wrong medication or wrong dose and for the wrong length of time.
•       Take poor quality medications.
•       Develop TB disease again, after being treated in the past.
•       Have limited or no access to health resources and treatments.

The vaccine

The Bacille Calmette-Guérin (BCG) vaccine offers some protection from developing active TB, especially in infants and children. It reduces the risk of disseminated TB, a form of TB that spreads from the lungs to other organs, which is lethal in children (e.g. TB meningitis). However, BCG vaccine does not reliably prevent pulmonary TB, which is the most common form of TB in adults.

In addition, the administration of BCG vaccine can sometimes cause a false positive result in a TB skin test and cause some confusion when trying to diagnose TB. There is an urgent need for a new, effective and safe vaccine for all age groups and for people with HIV. An effective vaccine is one that will prevent all forms of TB including drug-resistant strains.

What you can do

People at high risk are those who:

•       Have TB symptoms.
•       Have HIV infection.
•       Have a condition that weakens their immune system (e.g. diabetes, cancer).
•       Work in hospitals, prisons, schools or long-term care facilities.
•       Travel or live in areas with high TB rates.
•       Are born in a country with high TB rates.
•       Have never had a skin test before or have no record of the last result.
•       Live in crowded and unsanitary conditions.
•       Are mal-nourished and/or abuse drugs or alchool.
•       Are heavy smokers.
•       Have been in close contact with someone diagnosed with TB disease.

If you think you have been exposed to TB, get a TB skin test. The TB Mantoux skin test is one way to find out if you are infected. Should there be a need to distinguish between a prior BCG vaccine and a positive skin test, a blood test may be necessary. If you are not sure, talk to your doctor. TB can be prevented, even if you are at risk.

Photo Courtesy of: Microbe World