Millions of adolescents across Africa may unknowingly be battling asthma because they have not received a diagnosis from a clinician and, therefore, are not receiving the necessary treatments, a new study has found.

Published last week in the research journal The Lancet, the study’s findings are critical for a continent that has produced little data about the scale of asthma despite the condition being one of the most common causes of chronic respiratory deaths on the continent.

Asthma, which affects the lungs and causes difficulties in breathing, often starts in childhood or adolescence. It is a condition that affects many adolescents worldwide with an estimated 76 million young adults suffering from it in 2019, according to the National Library of Medicine, part of the United States government.

There is no outright cure for asthma that develops in childhood, but treatment can relieve symptoms, which often continue well into adulthood, according to scientists.

Here is what we know about why a silent asthma epidemic could be harming children in some African countries:

What did the study find?

A team of researchers led by investigators at Queen Mary University of London (QMUL) discovered that 12 percent of adolescents in six African countries had severe asthma symptoms but the vast majority of them – 80 percent – had not been diagnosed by a health expert.

The study, which was conducted from 2018 to 2021, focused on 20,000 children aged 12 to 14 in schools located in urban areas: Blantyre in Malawi, Durban in South Africa, Harare in Zimbabwe, Kampala in Uganda, Kumasi in Ghana and Lagos in Nigeria. Durban had the highest number of pupils with asthma symptoms while Blantyre had the lowest.

One-third of students who already had an asthma diagnosis and were presenting with severe symptoms were not using any medication to control the condition because they did not view their condition as serious and had poor knowledge of asthma therapies, the study also found.

“Adolescence is a particularly interesting age to look at,” Gioia Mosler of QMUL, who acted as research manager of the study, told Al Jazeera. “It is the time of life with the highest prevalence of asthma. It is also the time when we all form many of our perceptions of health and our body that we then carry into adulthood.”

It was not possible to generalise the results because of the different conditions in each African city, the researchers said. However, if their results are extrapolated, it could mean about 15 million adolescents have undiagnosed asthma symptoms in sub-Saharan Africa, Mosler noted.

Researchers used questionnaires in the initial phase and later conducted more rigorous lung function tests usually used for clinical diagnosis of asthma to determine which children likely had the disease.

What is asthma and why is it afflicting African cities?

Asthma is a chronic, often lifelong respiratory disease characterised by acute inflammation of the airways and airflow obstruction that affects 262 million people worldwide, according to the World Health Organization (WHO).

About half of those affected may be in Africa. The most recent estimate is from 2010 when 119 million were projected to be suffering from asthma on the continent, according to a 2013 study in the archives of the US National Library of Medicine.

Asthma can be triggered by pollen, dust, or particles from burning waste or other material. Symptoms often include difficulty breathing, wheezing, tightness in the chest and coughing.

Although rare, severe asthma can lead to death. About 455,000 people died from the condition in 2019, according to the WHO, mostly in low- to middle-income countries. Mortality rates in Africa are not clear although country-level studies have been conducted. In Uganda, for example, asthma deaths have been estimated at 19 deaths per 1,000 people per year. In contrast, Mexico records 10.41 deaths per 100,000 people, according to studies.

The exact causes of asthma are unknown, but asthma can be genetic. Environmental factors like changes in weather and air pollution are also common triggers linked to developing asthma.

In African cities, the high number of asthma cases has been linked to the continent’s rapid urbanisation and rise in pollution.

At least two-thirds of the world’s people live in cities. However, Africa has the fastest urbanisation rate in the world (3.5 percent growth per year compared with 1.8 percent on average) with big cities expanding and small towns growing.

While this provides economic opportunities, expanding urban centres also mean more polluted air caused by concentrated energy use, exhaust from cars, uncollected waste and a host of other factors that can trigger asthma.

A higher incidence of asthma in South Africa is likely linked to high cases of bronchitis, according to the Clean Air Fund. The country, which is reliant on polluting coal plants for electricity, has one of Africa’s worst air pollution levels.

The climate crisis is causing more asthma cases as well, researchers say. Increased exposure of vulnerable children to dust and wildfires that are intensifying globally because of global warming could occur, according to experts.

How prevalent is asthma in Africa?

Total asthma cases on the continent went from 94 million in 2000 to 119 million in 2010, according to the 2013 study.

Adolescents make up about 14 percent of the asthma cases in Africa although the numbers vary widely: In Nigeria, children make up about 13 percent of the cases while in South Africa, they make up about 20 percent.

Some studies showed there are disproportionately higher numbers of premature deaths and severe cases of asthma in African and other low-income countries largely because of inadequate healthcare systems, resulting in underdiagnosis and undertreatment.

How is asthma treated?

Asthma is ideally managed via two approaches: short-acting inhalers or tablets that expand the air passageways and allow more air into the lungs during an attack. There are also longer-term therapies that can also come in the form of preventive inhalers or tablets and that are used daily to prevent attacks from occurring.

In most African countries, however, asthma cases are treated on a crisis-by-crisis basis rather than being controlled over the longer term, researchers said.

The costs of treatment, even for short-term relief, are high. In Nigeria, which is in the grips of one of the worst economic crises in a generation, inhaler costs have nearly tripled in the past year alone from about 2,800 naira ($1.70) to 7,500 naira ($4.57). During the recession, pharmaceutical giant GlaxoSmithKline has exited the country, causing a scarcity of its highly sought-after brand of inhalers.

Why are cases going undetected?

Many asthma cases are undiagnosed because there is generally poor knowledge of the severity of the condition or how it can be effectively managed, researchers said.

In the QMUL-led study, researchers found that among adolescents who had previously been diagnosed with asthma, only half knew that young people die from asthma in their country. More than half of them did not realise that using a spacer – a simple plastic breathing tube with a valve – attached to their inhalers would allow the medication to get to the lungs much more easily.

Furthermore, despite the economic growth linked to rapid urbanisation, poverty and economic inequality remain problems across Africa, meaning many do not have access to healthcare.

About 60 percent of urban dwellers in Africa live in slums, according to UNICEF. Many adolescents in these settings do not have access to regular health checkups or even emergency care, researchers said.

Delayed diagnosis means children and young people risk more severe lung complications as a result of lack of care, Rebecca Nantanda, a senior research fellow at the Makerere University Lung Institute (MLI) who led the study in Uganda, told Al Jazeera.

One severe condition that can be triggered by untreated asthma is chronic obstructive pulmonary disease (COPD), which causes daily wheezing and a mucus-filled cough. Untreated asthma can also cause more than just physical symptoms, Nantanda added, and can negatively impact the way children connect with their peers because they tend to miss school often.

“[Asthma] affects their education and other activities like sport and play. It also affects their mental and psychological wellbeing due to stigma, chronic illness, stress, worries and anxiety,” she said.

What is the solution?

In the longer term, the WHO says controlling air quality in cities is imperative to drive down the number of people with asthma.

Researchers, meanwhile, are calling on African governments to increase investment in asthma treatments: both in long-term and short-term relief medication rather than push funds only into quick relievers.

“Most hospitals might focus on treating the asthma attacks and exacerbations, but these are more costly to the patient and health systems,” Nantanda of MLI said. “Governments need to invest in proper long-term care for asthma patients because, in the long run, it is cheaper and, therefore, more affordable.”

Working with drug manufacturers and other key players to negotiate subsidies for asthma medicines and diagnostics is also crucial, she added.

One way to fight underdetection in particular is to ramp up asthma awareness among students in schools, Mosler of QMUL said.

“Mobile clinics that visit schools could be a very effective way to screen,” Mosler said, referring to a method she noted has been tested in low-healthcare areas in the US with some success.

“The mobile clinic could then provide diagnosis and treatment directly at schools to those who have symptoms. Most African cities have good school attendance at the start of secondary schools. … [That] could provide an excellent way to address the problem,” she said.