What causes TB?
TB is caused by bacteria that are spread (by coughing, sneezing, talking) through the air from an infected person. Although it spreads via microscopic airborne droplets, like a cold or the flu, it is much harder to get. You must be around someone who has a lot of TB bacteria in their lungs for a lot of time, such as co-workers or family members.
Once the bacteria are inhaled, they lodge in your lungs and start growing. If you have a healthy immune system, your body fights it and you won’t become ill or contagious to others. However, the bacteria will develop into active, contagious infection if your immune system is weak and unable to fight the infection. Active TB disease can happen within days or weeks in a patient with a weak immune system. Or, it can develop months or years later, when your immune system grows weaker. Your chances of quickly developing active TB are greater if your immune system is weak when you are first exposed.
TB is hard to catch because TB germs cannot live on surfaces. You can’t get it by touching something the infected person has touched. It can’t be transmitted by shaking hands, sharing food or drink, or from faucets or toilets. Active TB patients are no longer contagious after they’ve had at least two weeks of treatment.
In the United States during the 1980s, TB cases increased rapidly because of the spread of HIV and AIDS. HIV is a virus that suppresses the immune system, making it harder for the body to fight off TB bacteria. HIV-positive patients have a high risk of getting active TB disease. They are also more likely to have latent TB progress to active TB.
Another fairly recent cause is the development of drug-resistant TB. Drugs used to treat it lose their ability to kill TB bacteria. Drug-resistant strains develop because patients don’t take their treatment medications correctly, or don’t complete the full course of treatment. When an antibiotic fails to kill all the bacteria it’s targeting, the surviving bacteria mutate and are able to resist antibiotics.
TB is more likely to develop if you have certain risk factors. They include:
- Weakened immune system that is caused by having HIV AIDS, diabetes, severe kidney disease, cancer or cancer treatment, anti-rejection drugs for an organ transplant, malnutrition or very low body weight, being very young or very old, or taking medications for rheumatoid arthritis, Crohn’s disease or psoriasis.
- Living in or traveling to areas with high TB rates, such as Africa, Asia, Caribbean, Eastern Europe, Russia or South America.
- Alcohol or IV drug abuse
- Smoking or using tobacco
- Working in health care
- Living or working in a residential care facility such as a prison, nursing home, or homeless shelter