Andrew Speaker became a celebrity overnight. He’s not a movie star or an athlete. He is known for globetrotting around the world while infected with a dangerous form of tuberculosis (TB) known as extensively drug resistant tuberculosis (XDR-TB), despite doctors urging him not to travel.
In fact, XDR-TB is considered to be such a threat to global health that Mr. Speaker has been officially quarantined by his government until he shows he is not contagious. Until then, he will be living in the isolation ward of a hospital.
What is TB?
TB is a disease caused by the bacterium Mycobacterium tuberculosis (M. tb). M. tb is an airborne pathogen, meaning you can be infected by breathing in the bacteria that has been coughed, sneezed, or spit out by people who are contagious for TB.
Did You Know? 1/3 of the world’s population is infected with dormant (non-infectious) TB. But don’t worry about getting TB from the cutie in your math class: 80% of the TB cases worldwide are in Asia, the former Soviet Union and Africa. TB is not common in North America. Once inhaled into the lungs, M. tb lives a cushy life. The immune system will try to kill it, but M. tb hides out in macrophages. Macrophages are white blood cells and are the very cells hunting and trying to kill the M. tb! Talk about keeping your friends close and enemies closer!
90-95% of people who become infected with M. tb can fight the infection. The 5-10% who get sick usually have some type of immunosupression – that is, their immune systems don’t work properly. This group includes young children, the elderly, and people with other diseases, especially HIV.
People can be infected with M. tb and not be contagious; their immune system is not strong enough to completely eliminate the infection and while they look healthy, they still have live M. tb hiding out in their lungs. Their M. tb level is not high enough to cause things like cough and fever, but once their immune system gets weakened, this is enough for disease to progress.
What is the difference between TB and XDR-TB?
XDR-TB is a rare type of TB. The M. tb bacteria that cause the infection is harder to treat since the bacteria are resistant to most of the drugs we have to treat it.
Did You Know? There is a TB vaccine, but it’s not very good at preventing disease in adults. It’s used to vaccinate children in areas where TB is common TB is treated by using 2 - 4 different antibiotics at the same time for at least 6 months. If a person being treated for TB stops taking their antibiotics early (because they feel better), the M. tb can develop antibiotic resistance.
If a person relapses (M. tb bacteria from the first infection wasn’t completely killed and can cause a new infection), the M. tb may be resistant to some or all of the antibiotics they were taking before. The drug resistance is so severe that some XDR-TB patients have to resort to surgery to remove infected portions of their lungs. Only half of the people who get XDR-TB survive, and the chance of survival drops to only 10% for people also infected with HIV.
The new face of TB
Although Mr. Speaker will be known as “the XDR-TB guy” for a bit, he’s probably going to have to live with TB for the rest of his life. One thing that his doctors can’t figure out is where he got infected.
TB is usually associated with poor, overcrowded living conditions (homeless shelters and prisons), and areas with a high incidence of HIV. Mr. Speaker is a well-off lawyer who lives is Atlanta and is, in fact, the anti-TB patient.
Did You Know? Testing new drugs and proving they are safe is a slow process. There are 7 new anti-TB drugs being tested right now, but it will probably be 2019 before we get a new one. We’re just really lucky that he wasn’t contagious during his travels. One good thing that’s come out of this is that governments, airlines and disease specialists are now forced to examine how to control the movement of contagious individuals and slow the global threat due to infectious diseases.
Salyers, A. and Whitt, D. (2002). Tuberculosis. Bacterial Pathogenesis: A Molecular Approach. p.291-310. Washington, D.C. ASM Press.
The World Health Organization’s FAQ on XDR-TB
Textbook of bacteriology
Marris, E. Extreme TB strain threatens HIV victims worldwide.
Nature. 2006. 443, 131.
Daniel, T. M. The history of tuberculosis. Respiratory Medicine. 2006. 100, 1862-70.
Also, check out the attached PDF from the CDC on TB – an informational pamphlet distributed by the CDC to promote TB awareness and education.
Nancy is working on her PhD at the University of Toronto, studying how the sexually transmitted infection gonorrhea affects the immune system. When she\'s not in the lab, she is probably playing ultimate frisbee.