Guidelines for Preventing Opportunistic Infections Among Hematopoietic Stem Cell Transplant Recipients

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What Is The Cause Of The Spread Of Tuberculosis, An Infectious Disease That Has Plagued Humanity For Many Years?

Jun 26, 2024 23:00:00 The plague was a terrible disease that raged from the Middle Ages to the early modern period, killing many people. If not properly treated, the plague is known as a dangerous infectious disease, with a mortality rate of almost 100%, but in modern times, advances in medical technology have kept the number of deaths to around 2,000 per year. However, tuberculosis still kills hundreds of thousands of people a year , making it a threat to medical care. The science-related YouTube channel Kurzgesagt explains about tuberculosis.

This Disease is Deadlier than the Plague - YouTube

Even today, with advances in medical technology, tuberculosis remains the leading cause of death from infectious diseases. In 1815, one in four people in the UK died from tuberculosis, and it is reported that over the past 200 years, approximately one billion people have died from tuberculosis.

According to Kurzgesagt, one in four people alive today is infected with

tuberculosis bacteria . However, we rarely hear reports of people being 'infected with tuberculosis.'

This is because the tuberculosis bacteria is highly contagious and perfectly adapted to the human immune system.

The bacteria usually enter the body through the airways and live in the lungs.

The lungs are protected by billions of macrophages, which ingest and kill bacteria, including tuberculosis bacteria, while keeping them alive.

But this is the strategy of Mycobacterium tuberculosis: macrophages trap bacteria they find in

phagosomes , which then dissolve them in acid. But Mycobacterium tuberculosis has evolved a capsule that makes it completely resistant to acid.

The tuberculosis bacteria then captures macrophages and remodels them to become their host.

The TB bacteria then multiply at a rate that is 60 times slower than other microorganisms that cause human disease, allowing them to multiply slowly in the body without being detected by the immune system.

Symptoms do not appear immediately after infection with tuberculosis bacteria. However, if the body's immune system is no longer able to suppress the infection,

the granulomas burst, causing dead macrophages and live tuberculosis bacteria to spread to the lungs.

As a result, the body's immune system goes into a panic and attacks the infected area.

As a result of attacking tuberculosis bacteria and other pathogens in an attempt to wipe them out, symptoms such as pneumonia, difficulty breathing, vomiting blood, and high fever appear.

Even if you receive treatment at a medical institution, the symptoms of tuberculosis will last for a few weeks to a few months, and if treatment is inadequate, it will gradually eat away at your body over a period of months or even decades.

In tuberculosis patients, fatal damage eventually destroys lung function and leads to death. In fact, it is estimated that 1.3 million people worldwide will die from tuberculosis in 2023 alone.

The scary thing about tuberculosis is its contagiousness. It is said that one patient infects about two to three people with

the new coronavirus that caused the COVID-19 pandemic in 2020, while a tuberculosis patient infects five to 15 people in a year.

Most of the infections are thought to be transmitted through droplets from coughing and sneezing.

Tuberculosis often spreads in crowded or poorly ventilated homes and workplaces, and during the Industrial Revolution, poor urban conditions led to the widespread spread of tuberculosis.

Today, it is possible to cure tuberculosis completely with four antibiotics taken over a four-month period.

These drugs were developed between 1940 and 1965, but they were never successfully distributed worldwide. Even today, two-thirds of all tuberculosis patients live in countries such as India, China, Indonesia, and Pakistan.

Furthermore, like climate change, TB is a slow-growing problem that has been ignored rather than aggressively combated, and as a result, the TB bacteria has become resistant to antibiotics in recent years.

Despite this, few new drugs have been developed for tuberculosis since 1965.

'If we can get more people to know about tuberculosis and get them interested in it, we can eradicate it from the planet,' Kurzgesagt argues.

'World's Deadliest Infection' Leaves Man With 'giant Crusty Wart' Sprouting From His Hand Amid 'worrying' UK Resurgence

A MAN suffered a rare side effect from a tuberculosis infection, breaking out it a crusty, yellow wart across his hand.

Dubbed the 'world's most deadly infection', tuberculosis (TB) is a bacterial infection that usually attacks the lungs and is spread through the coughs and sneezes of infected people.

The UK has seen worrying resurgence in TB cases in recent years

A man experienced a rare form of TB that caused a wart to sprout from his handCredit: The New England Journal of Medicine

But in a rare case, a 59-year-old man broke out in a giant, scaly wart as a result of the infection.

It comes as the UK sees a worrying resurgence in the Victorian disease, with 106 cases reported across England and Wales in the week leading up to June 16.

The patient, from China, had been suffering with a painful rash on his right hand for a year before visiting a dermatology clinic.

Doctors examined the wart, which covered the back of the man's right hand and part of his index finger too, observing "thick yellow-brown crusting" and an inflamed red border.

According to a report published in The New England Journal of Medicine, the 59-year-old had no other symptoms, aside from the wart and the pain it was causing him.

The doctors then took a tissue sample from the lesion, analysing it under the microscope and performing genomic sequencing.

They were able to identify Mycobacterium tuberculosis, the bacteria causing tuberculosis infections.

After a computed tomography (CT) scan of the man's chest showed no TB in his lungs, doctors diagnosed him with a rarer form of the infection known as extrapulmonary TB.

Tuberculosis Isn't Often Seen In Australia, But I Tested Positive For TB This Year

I knew something wasn't right when the lymph nodes in my neck began to swell, causing intense pain and headaches, unlike anything I'd experienced before.

But when my GP suggested doing a blood test for tuberculosis (TB) in April neither of us expected a positive result.

She was the second doctor I'd seen in three months — both were equally perplexed by my prior blood test results, which had ruled out COVID-19, the flu and other respiratory viruses and pointed to a bacterial infection.

Aside from having a rugby player's neck, I had moderate night sweats, loss of appetite, fatigue and flu-like body aches.

I didn't have a temperature, cough, runny nose or sore throat but it was clear my immune system was in overdrive.

Results from my first blood test in February showed I had "markedly elevated" levels of inflammation — more than 25 times above normal. Two months later it was higher again.

My results particularly caught the attention of the second GP, who was from India and had witnessed the burden of tuberculosis before moving to Australia.

Doctors told me I could have picked up TB during my short trip to Vietnam, but it could have been from previous travels before COVID-19.(Supplied: Fleur Connick)

"Have you travelled overseas recently?" the GP asked.

"Kind of," I replied. "My partner and I spent about a month travelling around Bali and Vietnam in October last year."

She reassured me it would be "very unlikely" and "very unlucky" to have contracted TB given I'd only spent two weeks in each location.

Indonesia is among WHO's top 30 high TB burden countries and recorded around 700,000 new cases in 2022. (Supplied: Fleur Connick)

I also did not meet any of the main three risk factors associated with TB: I wasn't born overseas in a high-risk country, nor had I spent three months or more living in one of these places, and I didn't have any household members or close contacts with TB.

As a precaution she prescribed a five-day course of strong antibiotics and recommended I have a specific blood test to detect TB if my symptoms got any worse.

I went downhill two days later.

The next time I spoke to my GP it was over the phone.

I remember the concern in her voice as she told me I'd tested positive for TB, and that we needed to determine if it was a latent or active infection.

She apologised for being the bearer of bad news and said she would be in touch.

The call ended and I burst into tears.

A million questions whirled inside my head: Was I infectious? If so, how many people could I have unknowingly infected? And, of course, can you die from TB?

I've learned a lot about TB since then. Here are some of the things I wished I'd known sooner.

So, what is tuberculosis?

TB is a highly infectious disease caused by the bacterium Mycobacterium tuberculosis, which can result in serious illness and death if left untreated.

It represents one of the most significant public health threats globally and was the second leading infectious killer after COVID-19 in 2022, causing an estimated 1.3 million deaths worldwide.

The disease typically spreads when people who are sick with TB expel the bacteria into the air, for example, by coughing or sneezing.

World Health Organization estimates of TB infection incidence in 2019.(Supplied: WHO / CC BY 4.0)

But, not everyone infected will become sick or contagious.

Most people will have a latent TB infection, where the body's defences control the bacterium, which can stay alive in a dormant or inactive state.

A global modelling study, published in 2016, estimated that a quarter of the world's population had latent TB.

However, in approximately 5–10 per cent of cases, the bacterium will overcome the body's immune system defences, progressing from latent infection to TB disease.

According to the World Health Organization (WHO), an estimated 10.6 million people fell ill with TB in 2022.

Most of those new cases live in the WHO's 30 high TB burden countries — which includes India, Indonesia, Philippines, Pakistan, and Vietnam — with almost half occurring in the South-East Asian region.

Vietnam is among WHO's top 30 high TB burden countries, recording more than 100,000 new cases in 2022.(Supplied: Fleur Connick)

What are the symptoms of TB?

Some people with TB disease may only have mild symptoms, while those with a latent TB infection will often have no symptoms at all.

Common symptoms of TB disease include a prolonged cough, chest pain, weakness or fatigue, weight loss, fever, and night sweats, according to WHO's Tuberculosis Programme team lead Kerri Viney.

"Often, these symptoms will be mild for many months, leading to delays in seeking care and increasing the risk of spreading the infection to others," Dr Viney says.

TB disease predominantly affects the lungs, and is known as pulmonary TB.

TB is caused by the bacterium Mycobacterium tuberculosis, which most often affects the lungs.(Wikimedia Commons: Mycobacterium Tuberculosis Bacteria, the Cause of TB (52764546631)/NIAID/CC BY 2.0.)

But TB can also affect other parts of the body, including the central nervous system (a condition known as TB meningitis), as well as the bones and joints, lymph nodes, abdomen, and blood. This is known as extrapulmonary TB.

Only people with pulmonary TB can be infectious.

The time it takes for a TB infection to become active varies from person to person.

For some, it can be shortly after infection, while others might not develop TB disease until years later when their immune system becomes weak.

The probability of this happening is much higher among people living with HIV, Dr Viney says.

Other risk factors include malnutrition, diabetes, smoking and alcohol consumption.

Is TB common in Australia?

The short answer is no.

The incidence of TB in Australia is relatively low, but experts say we must remain alert, particularly with the growing threat of drug-resistant TB disease.

TB disease is nationally notifiable in Australia, by both laboratories and clinicians, and all confirmed cases are reported to the National Notifiable Diseases Surveillance System.

However, this data does not include the number of Australians with a latent TB infection.

According to the Federal Department of Health and Aged Care, the national incidence of TB post-COVID has remained consistent with previous years.

In 2023, the rate of the disease in Australia was 5.3 cases per 100,000 people, with 1,430 TB notifications.

In total, 67 Australians were reported to have died due to TB from 2021 to 2023.

"Without treatment, the death rate from TB is high," Dr Viney says.

But TB is treatable and "usually curable".

'Every GP will be aware of TB'

It's not often that GPs see patients with TB, Tim Senior, a general practitioner based in south-west Sydney and Aboriginal health medical advisor for the Royal Australian College of General Practitioners, says.

"Having said that, I think every GP will be aware of TB and the potential for it to present," Dr Senior says.

"Even if we're not seeing it, it's there at the back of our minds."

The frequency of TB patients would also depend on the community profile and area a GP is working in, he adds.

For example, GPs working in the Northern Territory see more patients with TB than those in NSW or Tasmania.

The NT has the highest rate of TB in Australia, with most cases occurring in those born overseas and in First Nations peoples.

Due to its close geographic proximity to South-East Asia, studies have attributed the increase in TB cases to sporadic influxes of arrivals from neighbouring countries.

"People who are at highest risk of TB are Aboriginal and Torres Strait Islander people, and people from TB-epidemic countries," Dr Senior says.

"Being Aboriginal is a marker of exposure to all the disadvantages and risk factors that predispose you to [the disease], and that puts you at higher risk of TB."

This includes facing poorer living conditions and healthcare services.

How is TB diagnosed and treated?

TB infections can be identified through a tuberculin skin test or a blood test, known as an interferon-gamma release assay or Quantiferon TB Gold-Plus.

However, these tests cannot identify whether the TB infection is active or latent.

If the test is positive, you may have to do a chest X-ray, a physical examination, or a sputum test that looks for signs of the bacterium in mucous, to confirm if you have active TB.

Doctors use chest X-rays to diagnose TB disease of the lungs (pulmonary TB).(Flickr: Miliary tuberculosis/Pulmonary Pathology/CC BY-SA 2.0)

In my case, I returned two positive blood test results after my specialist suspected my first result was a false positive.

I also had a chest X-ray, which is used to identify pulmonary TB.

Thankfully my results came back clear. But, if a doctor suspects you have TB outside the lungs, you'll usually need to have a different test, such as a biopsy.

I was reassured my TB infection was most likely latent, and not active, so I was not infectious.

Two weeks later, I was prescribed a four-month course of an antibiotic called rifampicin.

Treatment for TB disease is slightly different and requires a combination of specific antibiotics (isoniazid, rifampicin, ethambutol and pyrazinamide) for at least six months.

This also varies for each patient, depending on their age, type of TB, and whether the strain is drug-resistant.

TB that is resistant to rifampicin and isoniazid is defined as multidrug-resistant TB. It is treatable by using second-line drugs, although they may not be as effective or available.

Drug-resistant TB continues to be a public health threat globally, Dr Viney says.

"Resistance to rifampicin — the most effective first-line drug — is of greatest concern."

Advice for travellers

Dr Senior says anyone planning to travel overseas should seek the advice of their GP "as there are a number of conditions to protect yourself and your family from when travelling".

Children under five are recommended to have the TB vaccination (called BCG) if they're travelling for more than four weeks to countries where TB is common. The vaccination needs to be given more than three months before leaving.

"People should see their GP if they have a prolonged exposure to someone with TB, or if they have an unexplained cough lasting longer than three weeks, with weight loss or sweating at night," Dr Senior says.

Immunosuppressed people are also more at risk of TB and "need to be more careful", he adds.

I tested positive for TB not long after starting a cadetship with ABC Science, but the whole team has been super supportive.(Supplied: Fleur Connick / ABC Science)

In my case, there is still some uncertainty about what strain of TB I picked up.

The specialist told me if the antibiotics are not effective and the TB becomes active, infecting my lungs, for example, they'll consider doing a sputum culture test.

It's been a month since I started taking the antibiotics, and so far, it's looking positive (touch wood).

While the list of side effects for rifampicin may be as long as the contraceptive pill, and I have to do routine blood tests to check my liver function isn't affected, I am grateful to have access to the treatment.

I am also eternally grateful that my GP picked up on the possibility of me having TB when she did.

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