October 17, 2021

I, Science

The science magazine of Imperial College

Why is urbanisation increasing disease prevalence? Tim Ellis looks to South Africa for answers.

capetown shantys

 Township near Cape Town, South Africa.

 “As a medical student we would often be sent to rural clinics on the outskirts of the city to help out the nurses. The clinics always seemed to be small, square buildings surrounded by dusty land and ringed by old wire fences. When we arrived at the start of the day, people would already be patiently queuing on benches circling the corners of the square building. Old gogos (grandmothers) with swollen legs, young men, painfully skinny with deep sunken eyes and faded t-shirts draped over bony collarbones, would be seated next to each other passing the time. There was often a sign saying ‘waiting time six hours’ at the entrance to the nurse’s office.”

Today, more than half of the global human population resides within cities, and this population is growing. But global urbanisation is not a single-species phenomenon – other species take full advantage of the urban resources available to them.

Biofilm of antibiotic resistant bacteria including Mycobacterium tuberculosis
Biofilm of antibiotic-resistant bacteria, including Mycobacterium Tuberculosis

The media continues to inform its audience with reports of emerging epidemics, outbreaks driven by increased proximity, and poor sanitation. The post-earthquake Cholera outbreak in Haiti in 2013 was marked as one of the worst in modern history. The recent Ebola outbreak vividly demonstrated the speed at which such a disease can spread. Confusingly however, the presence of the world’s biggest single pathogen killer, Tuberculosis (TB), gets off lightly when considering its media coverage, despite the 9 million new cases that arise each year. No place feels the weight of these numbers more acutely than TB-stricken regions of South Africa.

The urban environment of South Africa is Ground Zero for the inoculation and transmission of Tuberculosis on the African continent, with incidence rates stoked by HIV co-infection and poor patient compliance. The townships and more remote areas of South Africa provide an ideal landscape for the bacterial pathogen to replicate, leading to an estimated 390,000 new cases each year. A number of factors lead to this disproportionate incidence of TB, many of which are socioeconomic in their origin. Crowded and unsanitary living conditions, coupled with poor nutrition, provide ideal surroundings for infection to take hold. It is the treatment of this demographic that is pivotal in managing the disease on a global scale.

The lungs of a person diagnosed with tuberculosis
Tuberculosis visible in an X-Ray of a patient’s lungs

Not only do the townships of South Africa have some of the highest rates of TB in the world, they are rapidly becoming an epicenter for TB drug resistance, with some strains close to being completely untreatable. Furthermore, patients in the waiting room will often be HIV-positive, a virus renowned for its ability to cripple the sufferer’s immune system. This provides the ideal environment for further spread of TB within these vulnerable communities.

Socio-Economics: The Elephant in the Room

Although most of the media’s emphasis on antibiotic resistance focuses on medical provision and continued research, many argue that the heart of the problem stems from socioeconomic factors. With ten-strong families living in cramped single rooms, high levels of air pollution and restricted access to clean water, the townships of South Africa are a huge catalyst to the spread of disease throughout the country. Crowded living spaces bring increased contact with infected individuals. Poor diet and air pollution bring compromised immunity. This poses the question: why is funding targeting the treatment of these urban diseases focusing solely on treatment? Not only would patients’ health and quality of life vastly improve by funding clean living conditions, but so too would the prosperity of the area and the underlying economy.

Urbanization is the next stage of civilization for our species. This presents new challenges to our healthcare. With the growth of our cities, we must also grow in the way we combine disease management with a sustainable city expansion. Our new environment will no doubt facilitate sweeping new developments for our species, but it should not come at the expense of leaving healthcare in the green belt.

After all, this is not just our concrete jungle.

Tim Ellis is studying for a PhD in Pulmonary Nanomedicine
Introduction by Ashley Jacobs, a Research Fellow studying Clinical Immunology

Images: City, anekoho; Township, Diriye Amey; Biofilm, Kateryena Kon; X-Ray, Suttha Burawonk; Doctor, Leonie Broekstra;