What makes tuberculosis (TB) the world's most infectious killer?

In 2008, archeologists uncovered two

9,000-year old skeletons. There’s no definitive way of knowing what

killed these ancient people, but we do know their bones were infected

by an all too familiar bacterium. The ancient Greeks knew its consumptive

effects as phthisis; the Incans called it chaky oncay;

and the English called it tuberculosis. Today, tuberculosis, or TB, is still one of the world’s biggest

infectious killers, causing more deaths than malaria or

even HIV and AIDS. But what exactly is this disease, and how

has this pathogen persisted for so long? Typically, TB bacteria called

mycobacterium tuberculosis, are airborne. They travel into our airways and

infect our lungs. Here, immune cells called macrophages

rush to the infection site, attempting to absorb and break down

the bacterial invaders. In many cases, this response is enough

to remove the bacteria. But in individuals with other

medical conditions– ranging from malnutrition and HIV to

diabetes and pregnancy –the immune response may not be

strong enough to destroy the intruder. If so, mycobacterium tuberculosis will

reproduce inside those macrophages, and form colonies in the

surrounding lung tissue. As they infect more cells, the bacteria employ cell-degrading enzymes

that destroy the infected tissue, triggering chest pain, and causing

patients to cough up blood. The damage to the lungs leads to

oxygen deprivation. This begins a flood of hormonal changes– including a decrease in appetite and

iron production. From here, microbes can spread to the

skeletal system, causing back pain and difficulty moving; to the kidneys and intestines,

causing abdominal pain; and to the brain, causing headaches

and even impaired consciousness. These symptoms produce the

classic image of TB: weight loss, a hacking, bloody cough,

and ashen skin. This ghostly appearance earned TB

the title of the ‘White Plague’ in Victorian-era England. During this period, tuberculosis was

considered a ‘romantic disease,' because it tended to affect poverty-

stricken artists and poets– those with weaker immune systems. TB’s outward symptoms even helped

fuel the popular myth of vampirism. In spite of– or perhaps because of

these less than scientific concerns, this period also marked the first strides

toward curing TB. In 1882, the German physician Robert Koch identified the disease’s

bacterial origins. 13 years later, physicist Wilhelm

Roentgen  discovered the X-ray, enabling physicians to diagnose and track

its progression through the body. These techniques allowed researchers to

develop reliable and effective vaccines– first for smallpox, and again in 1921, when scientists developed the BCG

vaccine to battle TB. These developments laid the groundwork

for the modern field of antibiotics– currently home to our most effective

TB treatments. But, antibiotics fail to address a major

diagnostic complication: about 90% of people infected with TB

don’t show any symptoms. In these latent infections, the TB

bacterium may be dormant, only activating when someone’s immune

system is too weak to mount a defense. This makes TB much harder to diagnose. And even when properly identified, traditional treatments can take

up to 9 months, requiring multiple drugs and a high

potential for side effects. This discourages people from finishing

the full course, and partial treatment enables bacteria to

develop resistance to these drugs. Today, the disease is still prevalent

in 30 countries, most of which face other health crises that exacerbate TB and

trigger latent cases. Worse still, accessing treatment can

be difficult in many of these countries, and the stigma towards TB can discourage

people from getting the help they need. Health experts agree we need to

develop better diagnostics, faster acting antibiotics, and more

effective vaccines. Researchers have already developed a urine

test that yields results in 12 hours, as well as a new oral treatment that could

cut treatment time by 75%. Hopefully, with advancements like these, we’ll finally be able to make TB

exclusively a thing of the past.