Tuberculosis Through Time: Historic Burden, Modern Challenges

Despite being often thought of as a disease of the past, tuberculosis (TB) continues to pose a global health challenge, as emphasized by leaders at the CHEST 2024 annual meeting in Boston, Massachusetts.¹

Global respiratory leaders at CHEST 2024 underscored the ongoing clinical burden of tuberculosis, emphasizing that it remains a significant global health challenge that requires attention and awareness. | Image Credit: tashatuvango - stock.adobe.com

History of TB

TB is an infectious disease caused by bacteria that spread through the air when infected people cough, sneeze, or spit²; it most often affects the lungs. TB has affected humans for thousands of years, with evidence of it in ancient Egyptian mummies dating back over 4000 years.³ From the 1600s through the 1800s, it caused 25% of all deaths in Europe; similar numbers also occurred in the US.

Before Robert Koch in 1882 discovered Mycobacterium tuberculosis, the bacteria that causes TB, many thought the disease was hereditary.² It has also been known as phthisis, white plague, consumption, and wasting disease. Before the discovery of antibiotics, a TB diagnosis was considered a death sentence, with treatment limited to warmth, rest, and good food. Many patients were housed in TB sanatoriums to reduce the chance of the disease spreading to their families. By 1953, there were 839 sanatoriums with a capacity for 136,000 patients. Other treatments used in the early 1800s included vinegar massages, cod liver oil, and inhaling hemlock or turpentine.

Today, TB is known to be an airborne infectious disease, and its names indicate where it is (pulmonary or extrapulmonary) and how to treat it (drug resistant, drug susceptible, multidrug resistant, and extensively drug resistant). Also, it is primarily treated using antibiotics, namely Isoniazid, pyrazinamide, ethambutol, and rifampin.

After the discovery of antibiotics, the number of TB cases and deaths began to drop dramatically in the US. In 1992, there were 26,673 TB cases in the US, which decreased to 7174 in 2020; the US has one of the lowest TB case rates worldwide.

TB Diagnosis and Treatment

Although about 25% of the global population has been infected with TB bacteria, only about 5% to 10% will eventually get symptoms and develop the disease.

Those with latent TB infection are not contagious and do not feel sick, but patients who develop TB will experience symptoms like prolonged cough, fatigue, weight loss, and chest pain. Patients’ symptoms depend on where in the body TB becomes active, as it can affect the lungs, brain, spine, skin, and kidneys.

Patients with diabetes or weakened immune systems, along with those who are malnourished or use tobacco, are at increased risk for TB. However, Patients with HIV are 16 times more likely to fall ill with TB. It is the leading cause of death among this population, as HIV and TB speed up the other’s progress. Therefore, without proper treatment, nearly all people who have HIV and TB will die.

All persons with TB signs and symptoms are initially advised to use rapid molecular diagnostic tests. A tuberculin skin test (TST) and an interferon-gamma release assay (IGRA) can also identify TB infection.

Treatment is recommended for both TB infection and active disease through antibiotics. These medications must be taken daily for 4 to 6 months, and it is considered dangerous to stop earlier or without medical advice. Prematurely stopping medications can allow TB to become drug resistant. After becoming unresponsive to standard drugs, patients with drug-resistant TB require more toxic treatment with different medicines.

Similarly, multidrug-resistant TB is caused by bacteria that do not respond to isoniazid and rifampicin, the 2 most effective first-line TB drugs. This is treatable and curable by using second-line drugs, which are more expensive and toxic.

Bacille Calmette-Guerin (BCG) is a TB vaccine that helps prevent children from contracting severe disseminated TB or TB meningitis. Many countries with a high TB prevalence vaccinate infants with BCG as part of their pediatric TB control efforts. Conversely, it is not generally recommended in the US due to the low overall risk of TB infection.

TB Today

Despite significant advancements in the identification and treatment of TB, the disease remains a global challenge, with varying prevalence across different regions. It is the second leading infectious killer worldwide after COVID-19, with over 80% of cases and deaths occurring in low- and middle-income countries.

In 2022, most new TB cases occurred in the World Health Organization’s South-East Asian region (46%), followed by the African (23%) and Western Pacific (18%) regions. Of these cases, about 87% occurred in the 30 high TB-burden countries,⁴ with more than two-thirds of the global total in China, Bangladesh, India, Indonesia, the Democratic Republic of Congo, Nigeria, Pakistan, and the Philippines.³

During a session at the CHEST 2024 annual meeting earlier this month, Adrian Rendon, MD, PhD, president of the Latin American Thoracic Association, discussed the impact of the COVID-19 pandemic on TB within Central and South American countries.¹ He noted there was a huge underdiagnosis of TB cases since resources were more focused on COVID-19 during the pandemic.

Consequently, there was a significant increase in TB cases and deaths, with the death toll rising from 1.4 million in 2019 to 1.5 and 1.6 million in 2020 and 2021, respectively. Rendon added that this increase in TB cases and deaths post pandemic also occurred in the US.

“TB doesn’t know barriers,” he said. “TB travels around the world very easily with people. We were talking about pollution, climate change, all of these are fuel for TB because they increase the economic crisis and promote migration; TB uses those factors to move around the world.”

Also, John Buckley, MD, MPH, president of the American College of Chest Physicians highlighted the stark contrast between the declining prevalence of TB in high-income countries and its continued burden in other parts of the world. He expressed concerns that young US professionals may not be aware of the ongoing TB epidemic.

“I want to keep reminding my young colleagues, my young learners, that just because we don’t see it [TB] in our daily practice doesn’t mean it’s not an extraordinarily important issue,” Buckley said.

References

1. McCormick B. Global respiratory leaders call for collaboration, advocacy to tackle key health challenges. AJMC®. October 8, 2024. Accessed October 24, 2024. https://www.ajmc.com/view/global-respiratory-leaders-call-for-collaboration-advocacy-to-tackle-key-health-challenges

2. Tuberculosis. World Health Organization. Accessed October 24, 2024. https://www.who.int/news-room/fact-sheets/detail/tuberculosis

3. TB 101 for health care workers. CDC. Accessed October 24, 2024. https://www.cdc.gov/tb/webcourses/tb101/page2621.html

4. High burden countries for tuberculosis. Stop TB Partnership. Accessed October 24, 2024. Accessed October 24, 2024. https://www.stoptb.org/securing-quality-tb-care-all/high-burden-countries-tuberculosis