Tuberculosis is one of the deadliest infectious diseases in human history. Here's why.

USA Today

03-04-2025

Tuberculosis is one of the deadliest infectious diseases in human history. Here's why.
Show Caption
Hide Caption
Tuberculosis history and treatment
Tuberculosis is spread through the air from one person to another, says the Center for Disease Control and Prevention.
When most of us think of serious diseases that kill millions of people, the ones that come to mind are often the ones that get the most attention: cancer, COVID-19, heart disease and diabetes. But a disease that's been killing a shocking number of people for over a century is tuberculous.
Each year, tuberculosis kills some 1.25 million people globally and more than 10 times that number become infected with the disease annually, according to the World Health Organization. In fact, the disease is so prevalent that the organization has identified tuberculosis as one of the top 10 leading causes of deaths worldwide.
"Since its identification in 1882, over 1 billion people have died from tuberculosis, making it one of the deadliest infectious diseases in human history," says Dr. Richard Doyle, a practicing physician and clinical assistant professor of emergency medicine at Northwestern University.
Here's what tuberculosis is, how it's transmitted and how you can expect to have it treated if it affects you or someone you love.
What is TB?
Tuberculosis, also known as TB, is a bacterial infection that primarily affects a person's lungs. Its symptoms vary widely depending on how the slow-growing mycobacterium that causes the infection progresses across three different stages. These stages are known as primary, latent and active.
In the primary stage of TB infection, most people don't have symptoms or experience only mild ones like a low-grade fever, fatigue or coughing. In the latent stage, TB germs have survived in the lungs but are contained by the body's immune system, so no symptoms are present. Active TB is what occurs when your immune system is no longer able to suppress the infection, and it begins to spread and cause problems. This can occur soon after becoming infected, but more frequently happens months or even years after the infection has been contained in the latent stage.
"Only about 5% to 10% of people infected with TB develop the active form of the disease," says Amira Roess, a professor of global health and epidemiology at George Mason University in Virginia. When active, a TB infection primarily attacks the lungs, "but can also impact nearly any organ system in the body," says Doyle.
A persistent cough—sometimes with accompanying blood—is the most common symptom, says Dr. Cathy Hewison, a physician and tuberculosis advisor at the Paris-based humanitarian organization, Médecins Sans Frontières; but other symptoms are also common and include "fever, night sweats and weight loss," she says. Active TB can also cause a loss of appetite, chest or back pain, fatigue, difficulty breathing and even death.
Other diseases: What causes brain tumors? Here's why they're not that common.
Is tuberculosis contagious?
Active TB is highly contagious and spreads through airborne particles that are released when an infected person speaks, sings, coughs or sneezes and others in the room breathe in those particles. "This is why we often see large-scale outbreaks in crowded or closed settings," says Roess.
But she stresses again that just because a person gets the disease doesn't mean they will develop symptoms, and only those individuals with active TB "can transmit the bacteria."
Doyle adds that anyone infected with TB can potentially develop the active form of the infection, but people with weakened immune systems are especially vulnerable.
Interesting: One woman's viral fever question sparked a very real debate. Is 98.6 outdated?
How is tuberculosis treated?
The good news is that even if one is dealing with the active form of the disease, TB is still curable—but it requires "a prolonged course of antibiotics," says Doyle. These rounds of antibiotics usually last between four to six months, "and most people respond very well to treatment," says Hewison. Still, because treatment requires a combination of multiple drugs, "it can be difficult for patients to remain adherent for such a long time, especially when the drugs often have unwanted side effects," she says.
Another concern Hewison points to is that, during the course of treatment, "TB often naturally develops resistance to drugs." When this occurs and the initial rounds of antibiotics stop working, she explains, "harder and longer treatments are used that usually last six to nine months or as many as 18 months for especially resistant forms of the disease."
To prevent this, "treatment should always first be guided by drug susceptibility testing," Doyle says, "which can usually ensure the most effective medications are used."
More effective and shortened treatment options are likelier to occur the earlier the disease is identified. "If the infection is caught early and if a patient adheres to their medication," Roess says, "tuberculosis can be easily cured."