Tuberculosis

This dreaded infection has killed many famous people in the prime of their lives; Chopin, Keats, Robert Louis Stevenson, Napoleon, Colonel William Light, just to name a few.

Tuberculosis (TB) is caused by a bacterium, (mycobacterium tuberculosis). It is transmitted from an infected person by respiratory droplets.  The organism may stay silent or "latent" for a long period with the body's inflammatory response walling it off in a "tubercle" or "granuloma". Although the lungs are the most common site for this to occur, it can affect any organ of the body including bones, kidneys, lymph glands and brain. The TB germ can become active when that person's immune defence declines due to ill health (especially HIV), malnutrition, alcoholism, diabetes, old age, and immunosuppressive drugs.

Only those suffering from “active” TB, where the germ has invaded the wall of a bronchus and can therefore be coughed out, are infectious to others.  People with active TB are classically wasted with a chronic blood-stained cough. In the past TB use to be referred to as "consumption" because the sufferer was visibly consumed by it.

Facts to remember:

• 1 in 3 people on the planet has latent TB (much less in high income countries)
• Only 1 in 10 of those will ever get active TB.
• Only 1 in 10 of those active cases will be infectious to other people.
• Those exposed to the germ as children are most likely to get active TB later in life.

The spread of TB relates to crowded living conditions which is why the incidence has declined in the west with improved living standards, even before antibiotics.

The risk of acquiring tuberculosis during travel is low with country incidence rates being the best guide to risk of infection. It also depends very much on region of travel and travel conditions. Most travellers staying in mid-range hotels, visiting tourist sites and travelling in groups would have little, if any, risk of the disease.

On the other hand, humanitarian workers and those volunteering in low to low-middle income countries for long periods of time would have much greater risk of exposure.  In high-risk areas like sub-Saharan Africa, the Tuberculin Skin Test conversion rate has been estimated at 1.6% per year.

Top 20 countries by actual numbers of cases:

Angola, Bangladesh, Brazil, China, DPR Korea, DR Congo, Ethiopia, India, Indonesia, Kenya, Mozambique, Myanmar, Nigeria, Pakistan, Philippines, Russian Federation, South Africa, Thailand, Tanzania, Vietnam.

An added 10 by incidence:

Cambodia, Central African Republic, Congo, Lesotho, Liberia, Namibia, Papua New Guinea, Sierra Leone, Zambia, Zimbabwe

There is a vaccine against TB (BCG Bacillus-Calmette-Guerin) but it is only about 50% protective over a life time and has the potential to scar at the injection site. It is more effective when given to young children to prevent the most severe forms of TB.  Most countries with low rates of TB have abandoned its use. Australia reports about 5 active cases of TB per 100,000 population per year.

In highly endemic countries, that figure is in the hundreds. Many of our neighbours have high rates including Papua New Guinea, the Western Pacific, Timor-Leste and Cambodia.

• Fever
• Cough (> 2 weeks)
• Weight loss and loss of appetite
• Night sweats
• Fatigue
• Coughing blood
• Enlarged glands

A skin test (mantoux) or blood test (IGRA) can show whether or not a person has been exposed to TB. Other tests including blood tests, chest XRay and sputum culture are then needed to determine whether the condition is active or latent.

Preventive treatment with a simplified drug regimen is offered to healthy positive reactors based on balancing risk from the treatment and likelihood of active disease occurring. These decisions are usually made by TB specialists who are well versed in the potential side effects of the drugs used.  Consideration is given to factors such as:

• TB exposure at a young age which is more likely to activate later.
• Exposure to an active case. Most activations of latent TB occur within 2 years of exposure.
• Risk of becoming an active case e.g. due to HIV or the need to be prescribed immunosuppressive drugs.
• Occupations with high levels of public risk (teaching or nursing) should the disease become active.

Treatment of active TB requires taking several drugs for up to 12 months. An infectious person usually becomes non-infectious quickly once treatment starts. Treatment failures, including compliance issues must be monitored by specialist units to avoid the development and spread of multi-drug resistant TB.

Multidrug resistant TB that is impossible to treat is the future challenge.

WHO’s annual report on global TB was released in late October, 2024. According to the report, Tuberculosis has replaced COVID-19 as the leading cause of deaths due to infectious disease. Of concern was an increase in the number of new cases, up from 7.5 million in 2022 to over 8.2 million last year. Despite the increase in cases, the number of deaths fell slightly.

• Five countries accounted for 55% of the global TB burden (India (26%), Indonesia (10%), China (6.8%), Philippines (6.8%) and Pakistan (6.3%).
• Five risk factors were identified in the newly diagnosed cases. (undernutrition, HIV infection, alcohol abuse, smoking and diabetes).

WHO has adopted certain goals to reduce the global burden of TB. It is hoping to achieve a 90% reduction in the number of deaths and an 80% reduction in incidence rate by 2030, compared with those in 2015. The COVID-19 pandemic impacted greatly on the program but there are good signs that it is back on track.