Tuberculosis, the world’s oldest and deadliest pandemic, has been plaguing us for well over 4,000 years, with a relative of TB bacteria detected since the dinosaur age, and an ancestor having infected our early human ancestors. Indeed, the pathogen seems like ancient history — but as recent developments indicate, tuberculosis isn’t done with us yet.

As it happens, Mycobacterium tuberculosis, the bacteria that causes tuberculosis, is second only to SARS-CoV-2 as the leading cause of death by infection right now. And it’s on the rise,  according to the World Health Organization’s 2024 country report for the United States. In 2023, the most recent year for which they have data, there were an estimated 11,000 cases and 626 deaths. The U.S. resurgence reflects a global trend that has seen an estimated 10.8 million people become ill worldwide with TB in 2023. 

TB is a slow disease: it can take months, years or decades for an infection to result in symptoms. This is why the current outbreaks have actually been brewing for at least a year (“recent” transmission means within the past two years.)

In the decades and centuries we’ve lived with TB, it has taught us some painful lessons. Now, as it surges back with one of the largest outbreaks in the U.S. in several decades, still ongoing in Kansas, we can learn from the lessons it’s taught us over our decades and centuries of coexistence. As well as helping us fight TB, these lessons offer powerful tools to improve the health of Americans and protect us from our tiniest adversaries: such as the viruses that cause bird flu, mpox, COVID-19, HIV and even the common cold.

Take advantage of the good news: U.S. rates of TB are still low

“I remember 20 years ago as a grad student naïvely thinking that since it was clear that we had diagnostics and drugs for TB, we would be able to beat it and I might have to pursue a different line of research later in life,” Dr. Jonathan Stillo, a medical anthropologist at Wayne State University, said in an email interview with Salon. “Stepping back and thinking about it though, it is a little crazy.”

Why crazy? Because tuberculosis is curable in virtually all instances so long as the person is properly diagnosed and able to receive and complete the correct treatment for the strain they have.

“Yet TB is the world's top infectious killer, accounting for about 1.5 million deaths a year,” Stillo said. “And every single one of these deaths is an unnecessary, preventable death.”

As of 2023, the U.S. remains among countries with the lowest incidence of TB. But it’s also made little or no progress in reducing the number of new cases. More worrisome: although active, or symptomatic, TB is a reportable disease, latent TB is not.  So in 2024 Centers for Disease Control and Prevention still relied on 2011 to 2012 data to estimate that up to 13 million people in the U.S. have a latent tuberculosis infection — and the vast majority (80%) of TB cases in the U.S. result from longstanding, untreated latent TB.

So while there aren’t that many cases of active TB causing the familiar symptoms of coughing, fever, weight loss or night sweats, a huge number of people are at risk of it, given the right conditions. So, too, are their close contacts, who are at risk of acquiring latent TB from them if they fall ill. If you spend a lot of time in an enclosed space with someone who is frequently coughing, you can easily inhale the airborne droplets they expel: many children, who are in close, ongoing contact with their parents and whose immune systems are less developed, are infected in exactly this way.

At this very moment, far too many of the conditions are right in the U.S. for latent TB, carried by perhaps millions of people, to become active and for active TB to be passed on, kicking off  major spread of the disease like the outbreaks in Kansas.

Make sure people with TB can complete their full treatment

It shouldn’t be difficult to prevent TB epidemics. We simply need to identify everyone who has the disease and treat them, and also identify their contacts who are at risk of getting TB themselves. We can provide preventative treatment, and then also identify as many people as possible who have the infection without being sick and treat them before it can turn into active tuberculosis and then be spread to others. Easy-peasy. But the trick (or one of the tricks, as we’ll see) lies in treatment.

You’ve probably taken antibiotics for an infection and been told very sternly to finish the entire bottle of medication, even if you feel better after just a few days. The drugs can suppress the bacteria without killing them all, but if you stop treatment too early, they can surge back. Even worse, the ones that weren’t killed right away will be the hardiest among them, and so you may be performing your own personal experiment in artificial selection of the toughest bugs, an experiment that could leave you with an antibiotic-resistant disease. This means that the first line drug will no longer work and doctors will have to find a new medication to give you. 

Antibiotic resistance is already a very serious problem where tuberculosis is concerned, forcing doctors to use the small remaining number of medications they have to offer. And now, frighteningly, there is tuberculosis that is resistant to all known drugs to treat it. In 2023 there were 100 cases of drug-resistant TB but a far smaller number of multidrug resistant disease. That year, there were just 15 cases of what’s called pre-extensively drug-resistant TB, and just a single case reported of the worst kind: extensively drug-resistant disease. It is very important to keep those numbers as low as possible or we risk returning to the days when humanity really had no control over TB and it infected a staggering list of writers, artists, musicians, politicians and other luminaries, killing many in their prime.

But preventing resistance requires diagnosis and treatment, which is no walk in the park. Rather than a 10 day course of treatment, you must take at least one (usually four) medications every single day for six months, usually under supervision at a clinic. They have side effects, which range from the unpleasant, like nausea or fatigue, to the very serious, like kidney damage, depression or hearing loss, making it extremely difficult for patients under treatment to attend school or work, or take care of children. So it’s expensive and gruelling, to say the least.

“Let’s say TB services are scaled down, people don’t get the support that they usually have. They’re kind of left more to themselves. The chances of getting more drug resistant TB is high because they will stop treatment, and then they will get relapses, and then they’ll be treated, maybe with the wrong drugs,” Dr. Beate Kampmann, professor of paediatric infection and immunity at the London School of Hygiene and Tropical Medicine, told Salon in a video interview. “I’m pretty sure that the rate of drug resistant TB will rise.”

Prevent the spread of diseases that contribute to TB susceptibility

Co-infection with HIV has long been understood as a major risk in activation of latent TB into active disease. Of the 626 deaths recorded from TB in the U.S. in 2023, 86 of them among people with HIV, a common co-infection — nearly 5 % of TB patients in the U.S. that year were also living with HIV. Does this mean being HIV-free means no need to worry? Nope. Rather, it tells us that a population where infectious diseases weaken the immune system is a population at risk of outbreaks of TB; diabetes and chronic obstructive pulmonary disease (COPD), and immunosuppressive diseases beyond HIV are also associated with tuberculosis.

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Leaving infections untreated is thus a recipe for disaster, so it’s vital for the health of the American population as a whole to ensure all residents are able to afford timely medical care that helps eliminate viruses or keep viral loads undetectably low, and in the case of bacteria like tuberculosis, that allows patients to complete a full course of treatment without the interruptions that can allow partly-suppressed infections to surge back, and perhaps to become resistant to the antibiotics that were used.

President Trump’s 90-day freeze on foreign aid funding through USAID, and then the shut down of the organization itself, means an immediate halt to funding for global TB programs to diagnose, treat and prevent the disease (worth $406 million in 2024), and if not somehow reversed or this funding replaced before it’s too late, will increase the risk of TB and of drug-resistant TB worldwide, inevitably affecting rates in the United States over time. But the impact of a freeze or cuts to foreign aid also means a freeze on global HIV prevention programs, and this puts everyone, again including Americans, at risk of a major explosion of not just HIV but also antibiotic-resistant TB. Put together, we may be deliberately engineering a global catastrophe that could eventually return us to those bad old pre-antibiotic days of early deaths from TB among all classes.

Clean the air

In a December episode of her new podcast, Public Health is Dead, Daniella Barreto took listeners behind the scenes at the Orpheum, a Vancouver theatre built in 1927 to be a luxurious, comfortable venue — cunningly designed to provide excellent ventilation in order to prevent spread of disease, like the age-old scourge of tuberculosis, but more specifically the H1N1 influenza, which swept the world in that last year of WWI, killing 675,000 Americans. A couple of decades before that, Dr. Carl Flügge, a microbiologist, epidemiologist and hygienist, discovered that tuberculosis bacteria were spread in droplets freshly coughed into the air by TB patients, validating the idea that fresh air was important for prevention.

In a video interview with Salon, Barreto, a public health advocate with a masters degree in population and public health, explained that TB provides a great example of a disease where clean indoor air can reduce infection rates. And yet in a way, our historical understanding of tuberculosis as the paradigmatic airborne disease has resulted in an odd reluctance, including by infectious disease physicians, to accept that breathing in pathogens from the air is an important way people get infected by other diseases like COVID and even influenza, too. But in those diseases, which are caused by viruses, it’s not just droplets, but far smaller airborne particles that play the critical role in infection. This reluctance to think outside the TB box has resulted in people resisting the sensible use of respirator masks in health care settings. This is despite the risk of vulnerable patients entering hospital for a non-infectious complaint and coming out with a new  infection, even if not coughed on directly.

Physician conducting a medical examination of a dairy worker at the state tuberculosis sanatorium in Ah-Gwah-Ching, Minnesota, 1932. (Smith Collection/Gado/Getty Images)

It’s not Flügge’s fault we’ve missed the point. In fact, his real interest was in “all aspects of the environment in which infection transmission occurs and the environmental conditions that predispose to all manner of human disease,” as infectious disease researchers write.

In 1897, Flügge even “collated evidence that a variety of infections can be transported following aerosolization by coughing or even just breathing or speaking or following aerosolization of infectious agents by air currents of varying speed from various surfaces,” according to those researchers. But errors of interpretation made by American epidemiologist Charles Chapin a decade later resulted in everything other than sprayed droplets being dismissed as irrelevant to transmission, a persistent mistake that has endured until today, resulting in preventable deaths due to SARS-CoV-2 floating around as exhaled particles too small to be considered droplets.

Nevertheless, Flügge’s air-related lesson of tuberculosis remains vitally important, and is gaining supporters.

“We’re sort of at this precipice, I think, of a paradigm change where we’re understanding way more about aerosol transmission when it comes to COVID and other diseases like influenza,” Barreto says.

Ensuring clean indoor air as the designers of the Orpheum did in 1918; or as do proponents of the widespread adoption of indoor air quality standards (in particular the ASHRAE standard 241, which updates minimum requirements to reduce the risk of disease transmission through exhaled pathogens), or the DIY makers of cheap, easy to build Corsi-Rosenthal boxes to filter the air in schools and homes. Sunlight, too, is a great and timeless disinfectant: airy, open spaces don’t just allow air movement that reduces transmission risk  —  they actually let sunlight in where it can kill bacteria in the air. The old sanatoria in the Alps to which European TB patients lucky enough to have wealthy relatives might be sent focused on cleanliness, fresh air and sunlight, ample nutritious food and rest. It’s a prescription suitable for both treatment and prevention today — along with, not instead of, the medications that actually kill the bacteria in a patient’s lungs.

Focusing on implementation of ASHRAE standard 241 in buildings may be one of the highest return initiatives we could take to reduce prevalence of all sorts of infectious disease. This would make Americans less susceptible to the next pandemic, whether it’s the latest new COVID-19 variant, or H5N1 becoming capable of human-to-human transmission, or tuberculosis brewing in lungs for years before sickening many patients. ASHRAE standards are not mandatory, but can be adopted by states or cities as the energy code requirement for new buildings and renovations alike.

Another reason to clean indoor air is in hopes of mitigating the harmful effects of pollution from wildfires or vehicle exhaust on TB risk. A study of Northern California residents last year found carbon monoxide and nitrogen dioxide exposure, largely the product of vehicle emissions, was correlated with risk of tuberculosis. Also in California, a 2023 study found that each event that exposed residents to wildfire-associated tiny particles was associated with between 19 and 28% higher odds of a tuberculosis diagnosis within 6 months.

In addition to ventilation and filtration to clean the air, you can use light. At around the start of the 20th century, scientist Niels Ryberg Finsen developed a light-based treatment for lupus vulgaris, a form of TB that affects the face. Finsen’s work won him a Nobel Prize in 1903 and paved the way for light-based therapies in many other ailments and the more recent use of red and blue LED lights for skin care and some therapeutic applications. And yet, in the face of the COVID pandemic, interest in the potential of UV light has been confined to a small group of researchers, engineers and “makers” who have, for example, created devices using UV in a wavelength that makes it safe for humans to be in the room while they’re on. This is a powerful way of cleaning the air and an area of great innovation. 

Focus on poverty, equity and housing to prevent TB outbreaks that affect everyone

“If they live in a very crowded environment and [a person has] contact with someone who’s got active TB, they’re much more likely to get it. And if they’re in a place where there is poor ventilation, for example, and then there is a nutritional need,” Kampmann said. “If they also have HIV or some immunocompromised [condition], then they are a sitting duck to get active TB.”

As Kampmann explained, TB is the classic example of a disease where you must think holistically, and where social determinants of health are vital to understanding the dynamics of the disease. This has been known for decades or centuries: in the U.K., she explains, sunlight exposure in new tenement settlements built in Manchester during industrialization, and then the rising standard of living, both contributed to a decline in TB rates well before doctors had any meaningful treatment to offer their patients.

“So it is clearly very much a socioeconomic determinant disease,” Kampmann said. William Osler, often described as the father of modern medicine, put it like this: “Tuberculosis is a social disease with a medical aspect.”

Poverty, which forces people into poorly ventilated, crowded conditions in inadequate housing or shelters, and leaves them vulnerable to poor nutritional status, immune-weakening stress, and lack of health insurance, interacts with each of these other factors to put people at greater risk of being infected in the first place, and of greater risk of that latent infection progressing to actual TB.

“The active case is always just the tip of the iceberg,” Kampmann told Salon. “And under that [are] all those people who might be exposed or infected, and the ones who are exposed, like children who might not be infected, you want to give medicines to so that they don’t get it in the first place, and the ones who are already infected, it depends what age they are and whether they’re in a particular vulnerable group, whether you would give them a treatment or not.”

Finally, education is vital in both the seeking health care part of addressing TB and the sticking-with-treatment part. Inequality and marginalization are major factors blocking patient access to reliable, comprehensible and trustworthy information about how to protect themselves and their loved ones. Racism and persistently race-based differences in treatment and outcomes within the health care system erode trust, and make people unwilling to participate in the real shared effort that is proper and effective treatment for TB.

And, Kampmann said, the current climate in which fear of deportation or immigration status issues may prevent people from seeking health care is a climate in which TB may spread silently for a long time. Preventative treatment for people who don’t have tuberculosis but are close contacts of people who are likewise depends on trust in the health care system and everyone who might interact with it.

“Most people in the USA probably do not know how fragile the public health situation is — especially as it relates to TB,” Stillo said. And just because poverty makes TB more likely and harder to treat does not mean it is only a disease of the poor: take the 2007 case of an Atlanta lawyer with multi-drug resistant TB who took international flights to several European countries before flying home to the U.S., where he was forced into isolation, received surgery to remove the upper right lobe of his lung, and was sued by fellow passengers. A similar case occurred in 2013.

Strengthen public health agencies

“One might look at the low TB rate in the USA and think that the situation is good here. It is not. Our public health infrastructure is fragile, understaffed and under-resourced,” Stillo said. And public health infrastructure is key to preventing TB-related disaster.

This is an old lesson. “To the classic epidemiologic triad of agent, host and environment, tuberculosis adds the category of Health Services,” wrote Victor W. Sidel, Ernest Drucker and Steven C. Martin in a 1993 paper with a focus on NYC, where crowding, inequality and poor socioeconomic conditions had set off a resurgence of TB.

Indeed, historically, outbreaks of TB have generally dissipated when public health has made a real effort such that healthcare agencies have worked well together to share information, reach out to communities, and ensure both knowledge and medical services are accessible to everyone, whatever their socioeconomic status. It’s one reason TB rates have stayed relatively very low in the United States.

“The USA has maintained a low rate of TB, but by having a little bit of TB everywhere, it means that we must have well-funded and staffed local public health infrastructure to address this infectious threat (as well as other ones), Stillo explained.

Although the cost of health care and medicines are prohibitive for many people in this country, putting them at risk of the poor health status that increases susceptibility to tuberculosis, direct TB care is currently free for patients, mostly funded by the CDC’s Division of Tuberculosis Elimination, although this does leave out the substantial time patients in treatment lose to paid work, as well as transportation costs and childcare if needed. But the actual cost of treatment itself is very substantial, with some estimates for patients reaching $23,000 per person. It’s one of the reasons public health and infectious disease experts worry about what will happen under the new administration.

“Particularly [in] the current political climate where public health and specifically infectious disease has been identified as something that should be cut and deprioritized, [this] threatens the health of the whole country,” Stillo said. “I strongly support increasing the attention that we pay to chronic and noncontagious diseases as well, but it is not a zero sum game.”

And it’s not just treatment. The CDC, for example, provides free molecular sequencing to help public health laboratories detect mutations in the bacteria early, a vital service to prevent spread of antibiotic-resistant strains. Cuts to funding could be disastrous. So could cuts to jobs that support the careful tracing of patient contacts and provision of individualized treatment for people at risk of infection or already infected.

“If you don’t have any personnel to look after these people, they will get more disease, and that will be a snowball, infecting others and so on, and it will be over a period of time, because TB is a slow disease,” Kampmann said.

Also disastrous would be suppression of health data and information. Barreto said we’ve done a “horrible job” with public health communication during the ongoing COVID pandemic.

“I think trying to now do education for something else, on top of a public health system that’s in tatters and the CDC not being allowed to … share information, I think, is kind of looking like a recipe for disaster,” Barreto said. “But also if TB starts becoming more of a problem. Understanding around preventing disease transmission being important, I think, is just like a fundamental thing that somehow has gotten lost.”