A total of 1.8 million young people between ten and 24 years of age are estimated to develop tuberculosis (TB) every year, with young adults aged 20 to 24 years at the greatest risk of developing infectious TB, according to research published in the European Respiratory Journal .
The study provides the first ever global estimate of TB rates among people in this age bracket. Previous estimates categorised those aged up to 14 years as children and anyone aged 15 years and over as adults, resulting in a gap in our understanding of the scale of TB burden among young people.
The researchers say this group are known to be at a high risk of developing the disease, and that becoming ill with TB can hinder their ability to study, find work or care for their families. Attempts to tackle TB in young people have been limited, since the scale of the problem was previously unknown.
TB is an infectious disease that is spread by inhaling droplets from the coughs or sneezes of someone with the disease. Those who become sick often develop a serious cough, fever and weight loss. TB can be treated with antibiotics, but without treatment it is often fatal.
The research was led by Kathryn Snow from the Department of Paediatrics at the University of Melbourne, Australia. She explained: "We know from previous studies that TB risk gets higher during adolescence and that young people have unique needs during treatment for TB, but until now there have been no estimates of the total number of adolescents who develop TB.
"Adolescence is a critical period in our lives - many young people with TB are finishing high school, beginning their careers and starting families. The disruption caused by TB can have serious long-term impacts, but the scale of TB burden among this group has been generally unrecognised".
To estimate the global incidence of TB among young people as one group, Snow and her team separated existing data out in to three age bands: ten to 14 years, 15 to 19 years and 20 to 24 years.
The data came from the World Health Organization (WHO) Global TB database for 2012 and from more detailed TB surveillance statistics from Brazil, Indonesia, South Africa, Romania and Estonia. These countries provided a representative global spread of TB epidemics of different types and severity.
The researchers found that an estimated 1.05 million 20 to 24 year olds, 535,000 15 to 19 year olds, and 192,000 ten to 14 year olds developed active TB in 2012, totalling 1.8 million new TB cases among all young people.
Researchers point out that this is still an estimate and the real figure for the number of new TB infections across all ten to 24 year olds could be as high as three million globally.
South Asia had the highest number of new cases at 721,000 across all ten to 24 year olds, followed by Sub-Saharan Africa with 534,000 new cases of TB in this age group in 2012.
Snow said: "We think that TB risk rises in adolescence due to a mix of biological and social factors. Young adults aged 20 to 24 years are more likely to develop infectious TB than younger adolescents. This means young adults are more likely to come in to contact with infectious TB through contact with friends and classmates of the same age, while young adolescents have less contact with young adults.
"Many countries in South Asia and Africa have high rates of TB overall, as well as large populations of young people, which may explain why these regions have the highest burden of TB in young people."
She added: "Now that we have identified the scale of the problem, our next step is to try to understand the potential for targeting preventative measures specifically at young people in countries with intense TB epidemics.
"Health programmes should consider the special needs of young people with TB, which include continuing their education, keeping their jobs, and meeting their family responsibilities. These needs can be met by allowing young people to attend appointments at flexible times, and by protecting young people's privacy so that they are not discriminated against at school or at work."
The researchers acknowledge that a lack of high-quality data from some countries may affect the quality of the estimates, and say that as better data becomes available they hope to revise these estimates with greater certainty.
Professor Graham Bothamley, head of the European Respiratory Society's Respiratory Infections Assembly, said: "TB is still a major health concern and remains one of the top ten causes of death worldwide, despite being preventable and treatable.
"We already know that TB affects young workers most frequently, but until now the number of young people affected each year was unclear. The scale of the TB burden requires significant investment in communication to remove the stigma of diagnosis and to prevent delayed diagnosis. We must also work on developing different ways of delivering treatment, so that the impact on patients' work lives can be reduced."