“But hasn’t TB been eradicated?,” my seatmate on a recent flight to South Africa asked me. This question crops up pretty frequently when I tell people what I do for a living. I research the development of diagnostic tests for diseases using breath, sputum, blood and urine, and at the moment I am working on a diagnostic breath test for tuberculosis.
For most people in the West, TB seems to be a disease of the past, when it was still called consumption, and the ill were sent to sanitariums in the mountains or desert.
Wellcome Library, London, CC BY-NC-ND
But TB hasn’t gone away. In 2015 the number of TB cases in the U.S. rose for the first time in 23 years. In 2014 more than 500 people died from TB in the U.S. Even so, a lot of people have no idea that TB is still found here, or what a major health risk it poses in other parts of the world.
My seatmate didn’t know, for instance, that South Africa has one of the highest incidence rates of TB in the world, and that disease had killed least 96,000 people there in 2015.
Tuberculosis is an airborne killer
In 2015, TB killed 1.5 million people worldwide, and an estimated 26,000 people are infected each day. Prevalence is highest in sub-Saharan Africa, from Ethiopia to South Africa, and in Asia, particularly in India and China.
The disease is caused by Mycobacterium tuberculosis, an organism that has caused infection in humans since the stone age.
And it’s airborne – aerosols containing the bacterium remain suspended in rooms for hours after being coughed out by a person with tuberculosis. Once inhaled, the mycobacterium has a very real chance of taking up residence in your lungs, where it can lead to one of two conditions: latent TB and TB disease.
People with latent TB are infected, but don’t have symptoms and can’t transmit the disease. However, latent TB can transition to TB disease when a person’s immune system is suppressed, because of an HIV infection or malnutrition, for instance. In the West, people with latent TB are treated to prevent the infection from becoming active. About one-third of the world’s population has latent TB.
TB disease, on the other hand, is infectious. The body’s response to the bacterium leads to a hypermetabolic state, draining nutrition from the body, leading to loss of weight or wasting. With your metabolism in overdrive, you become a skeletal vestige of yourself, waking up drenched in sweat each night.
This is accompanied by a fight between the bacterium and immune system, which takes place in your lungs, leaving you with a persistent hacking cough that ends up producing a literal bloody mess.
A person with TB disease is contagious for as long as they have TB symptoms. If untreated, it will probably kill you and could spread to people who live and work with you.
In the West, if a person is thought to have TB, skin and blood tests are usually the first diagnostic tests conducted, and if they generate a positive result, chest X-rays are taken, usually indicating that the patient has a latent infection. If the patient experiences night sweats, loss of weight and a persistent cough, then a sputum culture from the lung is sent off for testing. The sputum culture is the diagnostic “gold standard” used worldwide to confirm an active TB infection.
Kids often have trouble producing sputum, so instead they inhale droplets of saline, which can help them cough up phlegm from their lower airway.
Getting a result from a TB sputum culture test takes at least three weeks. Newer tests could decrease the time-to-result to a few hours, though in practice, the turnaround time is usually a few days. This time lag is one reason why up to 40 percent of patients who are tested never return to the clinic to learn the result.
When a person is diagnosed with TB, they’ll begin treatment with antibiotics. The standard therapy is a daily cocktail of antibiotics for at least six months.
While drug resistance in most countries hovers around a few percent of all TB cases reported (which is still noteworthy), some places, such as Russia, report that drug-resistant TB makes up a whopping rate of 19 percent of total cases.
However, some strains of TB are becoming resistant to standard therapies. Globally an estimated 480,000 people developed drug-resistant TB in 2014. People infected with drug-resistant TB undergo a daily, painful injection plus daily oral, toxic drug cocktails for at least 18 months.
Even with treatment, if you are infected with extremely drug-resistant TB, the risk of dying can be greater than 70 percent at five years after a full course or treatment, far worse than Ebola and most cancers.
TB outbreaks are happening in the U.S.
TB is still active in the U.S., and it is most likely to appear in large cities. New York and Los Angeles, for instance, are among cities that have seen recent outbreaks. These cities maintain at least marginal surveillance, in which people are screened for symptoms when they arrive from a destination where it is endemic. If they are infected, patients are placed onto supervised treatment.
But TB outbreaks have also occurred well outside of major cities.
Just last year Vermont had a mini-outbreak, in which eight people were infected at a rural K-8 school. In rural Alabama, an ongoing mini-outbreak has already killed three people and sickened over 70 others, with more new cases expected. While U.S. outbreaks have not yet been of the drug-resistant kind, we can’t assume that this luck will hold.
More needs to be done to stop TB
The World Health Organization has released a strategy to end the global TB epidemic by 2030. But the WHO estimates that there is a US$1.4 billion funding gap each year for treatment implementation. Research is also underfunded to the tune of $1.3 billion.
To eliminate TB, we need better disease surveillance and monitoring in all countries, but especially locations where it is endemic, to help prevent outbreaks and get people into treatment. In addition, developing new diagnostics that can deliver results much faster and that don’t require laboratories is critical. And these tests need to work on adults and children.
Making sure that TB patients get the support they need to comply with the months-long treatment regimen will also help. For those with multidrug-resistant TB, we need humane quarantine systems and a pipeline of non-toxic drugs so they have a reasonable chance of survival.
If the number of people who still get infected with TB and the number of people who ultimately die from the disease are not impetus for us to pay more attention, surely the specter of a drug-resistant, airborne killer with a 70 percent death rate is a fate not worth tempting.