Introducing TB
Tuberculosis (TB) is a highly infectious bacterial disease caused by Mycobacterium tuberculosis. It primarily affects the lungs and is spread from person to person through the air when someone with active TB coughs or sneezes. TB remains a major global health problem, infecting around 10 million people and causing over 1.5 million deaths worldwide in 2020 (Global Health Impact).
If left untreated, TB causes severe lung damage and can be fatal. Even with treatment, TB requires taking multiple antibiotics for at least 6 months. Drug-resistant strains are on the rise, making TB more difficult to cure (Hassoun, 2015). TB also commonly co-infects with HIV, each disease worsening the other. Overall, TB has widespread detrimental effects on global health and economies.
The Scale of the TB Epidemic
Tuberculosis (TB) is one of the top 10 leading causes of death worldwide. According to the World Health Organization, over 10 million people fell ill with TB in 2020 (https://www.who.int/news-room/fact-sheets/detail/tuberculosis). It affects countries around the world, but over 95% of cases and deaths occur in developing countries. In 2020, the top 5 countries with the largest number of incident cases were India, China, Indonesia, the Philippines and Pakistan (https://www.cdc.gov/tb/statistics/default.htm).
TB has surpassed HIV/AIDS as the leading cause of death from an infectious disease. The sheer scale of the global TB burden demonstrates why increased funding and attention are urgently needed.
TB’s Health and Economic Toll
TB is an airborne disease that mainly affects the lungs (https://www.cdc.gov/tb/publications/factsheets/general/tb.htm). It can cause several symptoms including cough, fever, night sweats, and weight loss. Without proper treatment, TB can be fatal. The most common symptom is a bad cough that lasts for 3 weeks or longer. Patients may also cough up blood or phlegm from the lungs. Other symptoms can include chest pain, weakness, fatigue, chills, and loss of appetite (https://www.mayoclinic.org/diseases-conditions/tuberculosis/symptoms-causes/syc-20351250).
In addition to the health impacts, TB also takes an economic toll. TB patients often cannot work due to their illness and the need for prolonged treatment, resulting in economic hardship for themselves and their families. The economic costs of TB include direct medical costs for diagnosis and treatment as well as indirect costs due to loss of income. Globally, TB costs economies billions of dollars each year in direct costs and lost productivity.
The Rise of Drug Resistance
TB strains resistant to drugs are on the rise globally. Multidrug-resistant TB (MDR-TB), which does not respond to the two most powerful first-line anti-TB drugs, isofazid and rifampicin, is a growing challenge. According to the WHO, an estimated 450,000 people developed MDR-TB in 2020, and over l60,000 died from the disease. Only about 40 percent of people with MDR-TB successfully complete treatment.
An even more serious form of drug resistance called extensively drug-resistant TB (XDR-TB) has now emerged. XDR-TB does not respond to isofazid and rifampicin, plus any fluoroquinolone and at least one second-line injectable drug. Global trends show a rise in XDR-TB, with over 25,000 new cases in 2019.
Drug resistance leads to higher death rates for TB and allows it to spread more easily. Unless properly treated, one person with drug resistant TB can infect over a dozen others annually. To curb this threat, expanded prevention and improved access to drug susceptibility testing is urgently needed.
The Need for Increased Funding
TB remains a leading infectious disease killer, resulting in an estimated 1.5 million deaths in 2020 (WHO, 2022). Despite being preventable and curable, it continues to claim far too many lives each year. A key barrier in the fight against TB is inadequate funding for public health programs and research.
The estimated funding gap for TB prevention, diagnosis and treatment globally was $1.5 billion in 2022 and $1.6 billion in 2023 (WHO, 2023). This level of underfunding is disproportionate to the scale of the TB epidemic and its health and economic impacts. Many high burden countries face large funding shortfalls for their national TB programs and rely heavily on external donors like the Global Fund.
Increased investments are urgently needed to strengthen health systems, expand access to care, develop new tools and meet global targets. Fully funding the TB response is the only way to get on track to end TB as a public health threat and eventually eliminate the disease altogether. With the right funding and innovation, achieving a TB-free world is within reach.
Powerful New Tools to Fight TB
Significant advances have been made recently in developing new tools to diagnose and treat tuberculosis (TB). One major breakthrough is the creation of rapid molecular tests that can diagnose TB in just a few hours. Whereas traditional smear microscopy could take days to yield results, new automated cartridge-based nucleic acid amplification tests like the Cepheid Xpert MTB/RIF assay provide quick and accurate detection of TB bacteria as well as potential resistance to the drug rifampicin (WHO 2023). These new rapid diagnostics allow patients to start appropriate therapy sooner, improve treatment outcomes, and reduce transmission of infection.
In addition to faster diagnosis, new shorter TB regimens are making it easier for patients to complete the full course of treatment. Conventional TB therapy takes 6 months or longer, contributing to high rates of nonadherence. But 4-month regimens containing the drugs rifapentine and moxifloxacin are now recommended options showing similar effectiveness with improved completion rates (Gill 2022). Shorter regimens reduce burden on patients and healthcare systems.
Finally, pharmaceutical research has also yielded promising new drugs that can treat resistant TB strains which react poorly to conventional antibiotics. Bedaquiline and delamanid are novel agents that have been added to WHO guidelines as part of combination therapies for multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). Several other new compound classes also in the pipeline offer hope of better cure rates for patients with limited treatment options previously (Gill 2022).
Vaccine Development Challenges
The only currently available vaccine for TB is the Bacillus Calmette-Guérin (BCG) vaccine first developed in 1921. However, the BCG vaccine has demonstrated limited and inconsistent efficacy, especially in protecting adults against the pulmonary form of TB which is responsible for transmission of the disease. A meta-analysis found that the BCG vaccine reduces the risk of TB by 50% on average.
There are over a dozen TB vaccine candidates in clinical trials, but progress has been very slow. Most candidates in late-stage trials have failed to significantly improve upon the protection provided by BCG. Developing new and more effective TB vaccines faces many challenges including the complexity of the bacteria itself and the lack of immune correlates of protection.
Effective new TB vaccines are desperately needed to stop transmission and reduce the global burden of disease. Experts state that new pre- and post-exposure vaccines used in combination could potentially reduce TB incidence by 90%. However, the most optimistic prediction for the first new TB vaccine does not see licensure before 2027. Increased investments in TB vaccine research and development are critical to produce breakthroughs in coming years.
The Toll of TB-HIV Co-infection
TB often hits people when their immune system is already weakened. The immunodeficiency induced by HIV greatly increases susceptibility to active TB. According to CDC, untreated latent TB can quickly progress to active TB disease in people living with HIV, since the immune system is compromised by the virus. Without treatment, HIV infection also increases the risk of dying from TB.
HIV and TB form a deadly combination, each speeding the other’s progress. According to the World Health Organization, over 200,000 HIV-positive people died of TB in 2020 alone (source). Among people living with HIV, TB accounted for more than 40% of AIDS-related deaths (source). Tuberculosis is the leading cause of death globally among HIV-positive people.
The dual epidemic of HIV/TB co-infection continues to pose significant public health challenges. Treatment of latent TB infection is an important component of TB prevention and control efforts among people living with HIV.
Controlling the Spread of TB
Early diagnosis and proper treatment of active TB cases is critical to controlling the spread of infection. Those with active, untreated TB can spread the bacteria through coughing, sneezing or speaking. Early detection through skin or blood tests allows doctors to isolate patients and begin antibiotic treatment. Proper treatment results in patients becoming noninfectious usually within 2 weeks (CDC, https://www.cdc.gov/tb/publications/factsheets/prevention/ichcs.htm).
Infection control measures like face masks and improved ventilation systems in healthcare facilities can significantly cut down on transmission (National Center for Biotechnology Information, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5256350/). Frequent handwashing, covering one’s cough, and proper disposal of tissues are also key. Negative-pressure isolation rooms pump air out to prevent it from flowing to other areas of the healthcare setting (CDC, https://www.cdc.gov/tb/topic/infectioncontrol/TBhealthCareSettings.htm).
Contact tracing by public health departments finds those who may have been exposed to TB patients and screens them for possible infection or disease. This allows for early treatment and further reduces spread (CDC, https://www.cdc.gov/tb/topic/infectioncontrol/TBhealthCareSettings.htm). Wider screening programs in communities at high risk can also help identify cases earlier.
Eliminating TB in Our Lifetime
Global efforts are underway to try to eliminate TB, but major work remains. Organizations like the World Health Organization have adopted ambitious goals such as the End TB Strategy, which aims to reduce TB deaths by 95% and cut new cases by 90% between 2015 and 2035.
With enough commitment and innovation from the global health community, eliminating TB may be possible. New tools like rapid molecular diagnostics, new TB drug regimens, and vaccine candidates are cause for hope.
But continued action and funding will be critically needed. TB is the world’s deadliest infectious disease, claiming over 1.5 million lives in 2020. Drug-resistant strains are on the rise globally. And most TB cases and deaths occur in developing countries, which will require assistance to strengthen their health systems.
Organizations leading the fight stress that TB can be eliminated in our lifetime, but only through sustained efforts. As the WHO states, “Eliminating TB is everybody’s business.”
Sources:
https://www.who.int/teams/global-tuberculosis-programme/the-end-tb-strategy
https://err.ersjournals.com/content/27/148/180035