Before COVID, TB was the world's worst pathogen. It's still a 'monster' killer

Until the emergence of COVID-19, tuberculosis was the deadliest infectious disease in the world. How did it evolve from a terrible disease to a largely controlled one to the horrific plague it is now?

That's the question that science journalist Vidya Krishnan explores in her new book, Phantom Plague: How Tuberculosis Shaped History, released this month. It traces the spread of TB from the U.S. and Europe in the 19th century to lower-income countries — including Krishnan's country of India — where it continues to flourish today.

The answer, she finds, has a lot to do with lack of treatment, overtreatment or the wrong treatment. When antibiotics became widely available in the 20th century, the West had the resources to pay for them and cure and control TB. Poorer countries didn't. And when antibiotics did become available in lower-income nations, they were often overused. With antibiotic overuse came antibiotic resistance as pathogens learned to fight off the cures. The result is what Krishnan calls a "monster" version of the disease known as multidrug-resistant TB.

Newer therapies are available in wealthy countries to control this strain of TB, but they are still greatly limited in poorer countries. And that has allowed multidrug-resistant TB to thrive.

Nowhere on the planet is that reality felt more than in India. It has the world's highest incidence of TB — its 2.8 million cases annually account for more than a quarter of cases globally, according to the U.S. Agency for International Development. Within India, the city of Mumbai — a focus of Krishnan's book — is one of the hot spots for both TB and multidrug-resistant TB.

Krishnan, an award-winning writer based in India who has written critically of India's health-care system for The Atlantic and other media outlets, talks to NPR about TB's outsize impact on her country. This interview has been edited for length and clarity.

Why did you begin this book in New York in the 19th century?

I wanted to show how we repeat the same disease-spreading mistakes over and over.

Spitting is as rampant in Mumbai as it was in New York in the 19th and early 20th centuries, when men were determined to spit despite fines. [TB germs are in saliva, and spitting can propel droplets into the air and spread the disease.] Anti-spitting laws were hard to enforce because the habit was so ubiquitous. The struggles to pass laws to curb spitting are the same 100 years later in Mumbai and across India.

And like New York City in the 19th century, India is densely populated with poor people living in overcrowded, often unsanitary conditions.

Describe the housing projects for the poor in Mumbai and their result on TB.

They have become incubators for TB. Mumbai urban planning has focused on making cheap labor available in urban centers. So they built high-rises with barely 3 meters [just over 3 yards] between buildings. Some neighborhoods are so densely packed with people that, despite being by the shoreline of the Arabian Sea, people living there get no sunlight, no fresh air. One architect who I spoke to calls it "skylight robbery" because the lower floors get no natural light. The disease thrives in places with poor ventilation. And people live in tiny, crammed spaces.

And these crowded quarters are dangerous because TB spreads through the air — traveling on a cough, sneeze, spittle or even a laugh. Is TB in India then confined to the poor, who spend much of their lives trapped in unhealthy neighborhoods?

No. People living in [these] conditions go out. They take cabs. They take the bus. They work in the homes of the rich. So it spreads.

Why has TB been so difficult to control in India?

In India, there is corruption and lack of accountability in the health care system. And we have a system of highly privatized health care. Patients who can afford the private system often get overtreated, because the incentive for private doctors is to retain patients until every last rupee is taken.

I wrote about a patient named Shreya. She was misdiagnosed for years. Her body was carpet-bombed with antibiotics. If a doctor can't treat TB, they're supposed to send the patient to a tertiary center where the government provides free medicines.

Instead, you write that doctors kept treating her with drugs that didn't work.

By the time Shreya's family ran out of money [to pay for treatment] and took her to a government hospital, she was resistant to many antibiotics. The drugs that could treat her were locked in patents and severely rationed in India.

And for this reason, as you write in your book, Shreya's family sued the government to release a rationed drug that is in short supply in India.

After her parents went to court, she received bedaquiline, a drug that could have saved her early in her disease. But it was too late and she died. Her doctor said she had a "miserable end."

What's happening is mass medical negligence. If you are poor, you may be undertreated without compassion because the system is overwhelmed. If you are rich [or like Shreya's parents, able to provide some private care until the money runs out], you are overtreated and often not correctly.

What needs to happen for India to control the spread of TB?

For starters, global health cannot be funded by charity. Philanthropists are often invested in pharmaceutical companies, and that's a clash of interests. Philanthropy can provide some drugs and vaccines, but it doesn't address structural issues: The poor get undertreated and the rich get overtreated. Neither is good. We need to reform the system.

Two equally important things need to happen simultaneously. People need access to free medicines, counseling and care; and India needs public health awareness campaigns so people can learn how to protect themselves. Most residents are unaware of the scale of the TB outbreak.

What does TB's long history teach us about the current pandemic?

Basically, no one is safe until we're all safe.

Susan Brink is a freelance writer who covers health and medicine. She is the author of The Fourth Trimester and co-author of A Change of Heart.

Copyright 2022 NPR. To see more, visit https://www.npr.org.