Co-authored by C. Robert Horsburgh Jr.
The World Health Organization has just released its annual Global Tuberculosis Report. The report shows that even as tuberculosis (TB) rates continue to fall worldwide, the epidemic is larger than previously estimated, with 10.4 million new TB cases globally in 2015; over 95 percent of TB cases happen in low- and middle- income countries.
14 years ago, the Global Fund was established to finance efforts to halt the spread of HIV/AIDS, TB, and malaria. It has since become the world's largest funder of programs aimed at fighting these diseases, investing close to $4 billion annually. In the years since its inception, it has made tremendous progress. The last 15 years have seen a 37 percent decline in global malaria incidence, a 35 percent decline in new HIV infections and, lagging significantly behind, an 18 percent decline in TB incidence.
In the case of TB, gains against the disease had been driven by a 1.5 percent decrease in worldwide incidence every year since 2000. This falls far short of the 4--5 percent annual decrease that would be needed to reach the goals set by the "End TB strategy" for 2020.
TB is an airborne, infectious condition, most commonly affecting the lungs. Lung TB can be transmitted through coughing, spitting, or sneezing. It is an ancient disease, dating all the way back to prehistory, so old that the Egyptian Pharaoh Tutankhamun was once thought to have suffered from it. Symptoms include fatigue, loss of appetite, chills, fever, and, when the disease is in the lungs, a bloody cough. However, our immune systems are often able to impede the growth of TB bacteria, and the disease can remain latent in the body for years, or even a lifetime, without causing symptoms, until weakening of the immune system allows the disease to reappear. TB is therefore most hazardous to people with weak immune systems and is the leading killer among HIV-infected populations.
As the new report makes clear, the success achieved thus far in TB, even if modest compared with the dramatic drop in malaria and HIV infection rates, may be in jeopardy. In 2015, 1.8 million people died from TB, an increase from 1.5 million in 2014. Approximately one million of those infected with TB were children, and nearly 200,000 children died of TB in the past year. TB also complicates the treatment of other diseases. In 2015, fully 35 percent of global HIV deaths were due to TB. The disease is present in every part of the world, although it is particularly prevalent in the South-East Asia and Western Pacific Regions, where about 60 percent of new global cases can be found. But the burden of TB is heaviest in Africa, where, in 2014, the continent suffered from 281 cases per 100,000 people, markedly higher than the global average of 133 cases per 100,000.
It is important to stress that TB is curable. The treatment is antibiotics, administered regularly over the course of at least six months. Why, then, with a cure at our disposal, is our progress on TB so slow? The answer lies not in the treatment itself, but in our capacity to deliver treatment effectively, and in the broader conditions that weaken the health systems needed to help deal with the disease.
Since a single person with active TB can infect about 10 people in one year, preventing the burden of TB in populations is tied closely to the delivery of treatment. TB treatment rests on taking a course of antibiotics for several months that must be delivered via robust, well-managed treatment programs. The most effective of these programs is Directly Observed Treatment, Short -Course, or DOTS. Endorsed by the WHO, DOTS requires effective, established health systems to enable its implementation. Unfortunately, an unfinished antibiotic regimen can lead to the patient developing drug-resistant TB, or, worse, multidrug-resistant TB (MDR-TB). Because of the hazard posed by MDR-TB, incomplete or poorly-administered treatment programs can make the danger of TB even worse. MDR-TB can linger in infected lungs and spread through populations, contributing to the spread of the epidemic.
Engagement with reducing the burden of this preventable disease requires an investment in health systems, building on funding to sustain infrastructure that can support programs on a large-scale. While this is consistent with the newly formulated Sustainable Development Goals, it remains far from our modal delivery of aid to low and middle-income countries, which continues to rely heavily on vertical programs, funding individual disease-specific efforts.
It is worth noting two factors that add to the challenge of dealing with TB.
First, the inextricable link between poverty and TB contributes to our relative neglect of what we need to do to reduce the burden of this disease. The conditions of poverty--malnutrition, poor sanitation, living in overcrowded slums--are deeply conducive to the spread of TB, and also characterize populations, frequently neglected, at greatest risk of TB who have the most to gain from effective, well-financed health systems. When these conditions are improved, TB rates decline. This was the case in England and Wales between 1838 and the 1940s, when better housing, nutrition, and sanitation set the stage for a drop in TB mortality during that time from nearly 400 deaths per 100,000 people to less than 50 deaths per 100,000 people.
A second critical factor limiting our success in the fight against TB is stigma. Because of stigma, persons who suspect they have TB delay going to the doctor for fear of being identified as contagious, even though treatment renders them non-infectious within days. Because of stigma, persons diagnosed with TB want to conceal their treatment from friends and neighbors, making treatment completion more difficult. Communities must be engaged to raise awareness about the curability of TB and to embrace broad TB screening and treatment initiatives. The WHO estimates that over 30 percent of persons sick with TB are not even diagnosed as having the disease; stigma is a major reason for this failure.
With so many current TB deaths occurring in low- and middle-income countries, it is clear that any attempt to end TB will require an investment where it matters most, helping poorer countries build their health systems, raising awareness about TB, and engaging with the challenges of delivering health services to the poorest, worldwide. This is an investment that will pay rich dividends; nations with resources need to double down now.
Dr. Sandro Galea is the Dean and Robert A. Knox Professor at the Boston University School of Public Health.
Dr. C. Robert Horsburgh Jr. is a Professor of Epidemiology, Biostatistics, Global Health and Medicine at the Boston University Schools of Public Health and Medicine.