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Why Study Tuberculosis?

Tuberculosis (TB) is an infectious disease that is one of the top 10 causes of death worldwide — killing almost 2 million people each year — and one of the major research priorities for the Ma Lab and our collaborators.

The Insidious Global Reach of TB

Alarmingly, the World Health Organization (WHO) has estimated that about one-quarter of the world’s population is latently infected with TB without having symptoms. Why is the infection so widespread? This is in part because TB passes between individuals through the air by breathing in tiny droplets containing the bacteria that causes the disease, Mycobacterium tuberculosis (Mtb). According to the WHO and Centers for Disease Control and Prevention (CDC), these droplets can be suspended in the air for several hours and are commonly generated by TB patients through coughing, sneezing, speaking, or singing. People exposed to these droplets can be infected with Mtb, which either makes them sick right away, or can persist latently without causing symptoms for up to decades. People latently infected with TB have a 5-15% chance of developing disease symptoms, thus serving as a large source of future infection. Diagnosing TB adds to the challenge as symptoms are often mistaken for other diseases, which means that many sufferers unknowingly transmit the disease to others.

The Challenge of Treating TB

Although a TB cure exists, the treatment is difficult. Therapy requires the patient to take four different drugs every day for six months even for patients with drug-sensitive disease. The side effects are common and nasty.

The length of treatment coupled with the side effects causes many patients to stop taking the drugs before they are cured. This leads to a vicious cycle of people getting sick again, sometimes with bacteria that have become resistant to several of the standard TB drugs — this drug-resistant form of the disease is called MDR-TB. In 2016, the WHO recorded an estimated half a million cases of MDR-TB2. Of these individuals, only 2 in 10 were successfully diagnosed and began therapy. Treating MDR-TB is even more difficult — requiring up to 2 years of drugs, which include daily injections that frequently cause permanent hearing loss and over 14,000 pills in total. Even with this arsenal, MDR-TB is a lot harder to cure.  Only half of MDR-TB patients who begin taking drugs are successfully treated.

Research is urgently needed to improve treatment strategies for TB. Most of the existing drugs for TB were developed in the 1950s and 1960s — 70 years ago (PPT). Resistance to every one of these drugs has emerged.

To address this need, research efforts in the Ma Lab and our collaborators include looking for new TB drug targets by disrupting the way that the bacteria sense and respond to their environment, stimulating the immune system to help fight infection, and developing more effective ways to combine individual drugs into treatment regimens.