On March 24, 1882, Robert Koch, a German physician and microbiologist, announced to the world that he had discovered the cause of tuberculosis (TB), at a time when one out of every seven people died from the disease.
A century later, it was proposed that this day be recognised by the World Health Organisation as the official World TB Day, a proposal that was realised in 1997.
On March 24, therefore, we build public awareness about TB and take stock of the progress, challenges and triumphs mankind has made to contain tuberculosis.
Someone dies from TB every 22 seconds making TB the leading cause of death from a single infection, more deaths than from HIV and malaria combined. Africa leads as the region with the highest TB burden and contributes 15 of the 30 leading countries with most TB globally.
Infection with Mycobacterium tuberculosis (Mtb), the bacteria that causes TB disease, occurs when people breath in air containing the bacteria.
Worldwide, two billion people are estimated to be infected with TB with the majority (90 percent) having no symptoms (termed people with latent TB) because their immune system can effectively contain the infection. The other 10 percent develop active TB characterised by clinical symptoms like cough, weight loss, chills, fever and night sweats.
If the doctor ever told you that your Mantoux test was positive (swelling after instillation of TB antigens under the skin of your arm), it means you were once infected with Mtb even though you show no clinical signs. People with latent TB are at a greater risk of developing active TB, making the potential cases large enough to sustain the high mortality associated with active TB.
When people develop compromised immunity, for example coinfection with HIV (including treated HIV), cancer patients, immunosuppression treatment for other conditions, drug abuse and diabetes, they are at a greater risk of developing active TB.
Talking about tuberculosis reminds one of the BCG vaccine, administered at birth and the only licensed vaccine against TB. Although BCG is effective at preventing childhood TB, including TB meningitis, its efficacy wears off with age and fails to protect adolescents and adults from TB. Surprisingly, the BCG vaccine has the ability to prevent other infections particularly in children. It is for this reason that the BCG vaccine is being tested as a remedy for Covid-19.
Before 2020, things were looking up with efforts to achieve the audacious goal of ending TB by 2035 taking root, but the pandemic has disrupted the progress. The fear that came with contracting Covid-19 in large gatherings means it will be even harder to reach marginalised populations for diagnosis.
For the first time in four decades, it was demonstrated that short course treatment of four months was effective at controlling drug susceptible TB. Great strides were made with a new Phase 2b vaccine (M72/ASO1E) showing 50 per cent efficacy in preventing TB disease. Studies in monkey models of TB demonstrated that it is possible to achieve sterile immunity (totally prevent infection after administering vaccine) against TB.
As the world marks yet another World TB day, key challenges remain, including availability of drugs that are short course, less toxic and (urgently needed) formulations that are well tolerable in children. Diagnostics of TB need urgent refinement if we are to capture the “walking sick’” within our communities. Diagnosis has been particularly impacted because Gene Xpert machines designed for TB diagnosis have been “repurposed” to diagnose Covid-19 patients.
With only one licensed vaccine, there is a need to understand the mechanisms of protection of M72 vaccine in humans and sterilising immunity of intravenous BCG in animals.
Equally important, governments must improve social amenities to reduce crowding – in informal settlements and in correctional facilities. Resources to support research keep shrinking and governments must dig deeper into their pockets to avail funds to back up their commitments to end TB strategy.
All these efforts will amount to nought if malnutrition is not tackled as a priority.
Last but not least emergence of drug resistant TB is a worrying trend to contend with.
The efforts to end TB encompasses us all, and TB is a treatable disease but the first step towards that is knowing your TB status.
Dr Paul Ogongo is a research scientist at the Institute of Primate Research, Nairobi, Kenya.