When people think of the world’s deadliest infectious diseases, they often name HIV, COVID-19, or malaria.
But the true leader is tuberculosis (TB), which killed nearly 1.3 million people in 2023—more than 3,400 every single day.
The number of cases worldwide is climbing fast.
TB is caused by Mycobacterium tuberculosis, a bacterium that usually attacks the lungs but can spread to the brain, lymph nodes, bones, or kidneys.
It has been infecting humans for thousands of years, adapting and evolving to survive in the body.
Without treatment, TB can be deadly. Even with treatment, it can linger, go dormant, and return later.
In the United States, TB was largely brought under control in the 1950s with antibiotics like streptomycin and public health programs.
But progress was set back in the 1980s by federal health budget cuts and the AIDS epidemic.
By the early 1990s, new programs helped bring cases down again—until COVID-19 disrupted diagnosis and treatment. Now, U.S. cases are rising by about 7% each year, mirroring a troubling global trend.
Worldwide, TB reached its highest level of new diagnoses in 2023 since the World Health Organization began tracking the disease 30 years ago—8.2 million new cases.
More than one in four people globally are already infected, though the bacteria often lie dormant. A weakened immune system can activate the disease, even decades after infection.
Researchers at Washington University School of Medicine in St. Louis are tackling TB through the Mycobacteria-focused Program for Research and Innovation in Science and Medicine (MycoPRISM).
This initiative brings together scientists, clinicians, engineers, and public health experts to study how TB evades the immune system, develop new treatments, and improve prevention.
One of TB’s challenges is that it can survive the body’s immune attacks. In adults, it often stays in the lungs, shielded by a waxy coating that hides it from immune cells. In children, it can spread more easily to other parts of the body.
The only available vaccine protects children from severe complications but doesn’t prevent TB in adults.
Treatment typically takes at least six months with a combination of four antibiotics. If patients stop early—whether because they feel better or the drugs cause side effects—the bacteria can become drug-resistant, making the disease even harder to treat.
Some strains are now resistant to multiple drugs, posing a serious public health threat.
TB also carries stigma. People may hide their diagnosis out of fear of being judged or isolated. In the U.S., health departments often require directly observed therapy, where staff watch patients take their medication, to ensure treatment is completed.
The COVID-19 pandemic worsened the problem by delaying diagnoses, diverting public health resources, and leaving more people vulnerable due to weakened immune systems. Since then, TB has surged in many countries. In the U.S., states like California, Texas, New York, and Florida see the highest case numbers, though smaller states have had alarming spikes, like Kansas, where cases more than doubled between 2023 and 2024.
TB thrives where health systems are underfunded. Cuts to global health programs, including the U.S. Agency for International Development’s TB initiatives, have left treatment programs without the antibiotics they need. This not only leads to more deaths but also increases the spread of the disease.
WashU researchers are also studying other mycobacteria found in soil and water that can cause severe lung infections, particularly in people with underlying conditions like cystic fibrosis. These infections can be even harder to treat than TB.
Experts agree the world needs an effective adult TB vaccine, faster diagnostic tests, shorter treatments, and strategies to prevent reactivation of latent TB. They also stress that TB is not just a medical problem—it is tied to poverty, overcrowding, malnutrition, and lack of access to healthcare. Addressing these root causes is key to controlling the disease.
Despite its reputation as a disease of the past, TB is still very much a present danger—and one that respects no borders. Without renewed investment in research, public health programs, and global cooperation, TB’s deadly grip will only tighten.
As Dr. Jennifer Philips of WashU Medicine warns, “TB has evolved with us—and it evolves faster than we do. We have got to find ways to stay ahead.”
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Source: Washington University School of Medicine in St. Louis.
