Exceptional improvements in the survival of infants and children under 5 years of age, life expectancy, immunisation coverage, and tuberculosis control in Bangladesh are part of a remarkable success story for health in the South Asian country, according to a major new Series published in The Lancet. This is despite low spending on health care, a weak health system, and widespread poverty.

But the nation still faces considerable problems, including deep poverty and malnutrition, and this is being exacerbated by an evolving set of 21st-century challenges (eg, massive and rapid urbanisation, an upsurge in chronic and non-communicable diseases, and increasing vulnerability to climate change).

The six-part Series takes a comprehensive look at one of the "great mysteries of global health", investigating a story not only of "unusual success" but also the challenges that lie ahead as Bangladesh moves towards universal health coverage.

"Over the past 40 years, Bangladesh has outperformed its Asian neighbours, convincingly defying the expert view that reducing poverty and increasing health resources are the key drivers of better population health", explains Series co-leader Professor Mushtaque Chowdhury from BRAC in Dhaka, Bangladesh. "Since 1980 maternal mortality has dropped by 75%, while infant mortality has more than halved since 1990, and life expectancy has increased to 68.3 years - surpassing neighbouring India and Pakistan."*

According to the Series, what sets Bangladesh apart is its pluralistic health system in which many stakeholders including the private sector and non-governmental organisations (NGOs) have been encouraged to thrive and experiment. This has led to rapid improvements in access to essential services such as diarrhoea treatment, family planning, vitamin A supplementation, and vaccination coverage.

"Promoting an open culture of research-based innovation has made Bangladesh a pioneer in scaling up community-based approaches that have brought key health interventions to every household, making huge inroads into improving maternal and child health and reducing population growth"*, explains Series co-leader Professor Abbas Bhuiya from the International Centre for Diarrhoeal Disease Research in Dhaka, Bangladesh.

One striking example is tuberculosis treatment. By mass deployment of community health workers, cure rates escalated from less than 50% to more than 90% - among the highest in the world. Another is contraceptive use. By recruiting female health workers to deliver door-to-door family planning services, Bangladesh has achieved high (62%) contraceptive prevalence and a rapid fall in fertility from 6.3 births per woman in 1971 to 2.3 in 2010 - a rate unparalleled in other countries with similar levels of development.

Other factors that have had a big impact on the health of Bangladesh's population include a strong focus on reducing gender inequality through pro-poor and pro-women development programmes (eg, in education and microfinance), and improvements in natural disaster preparedness and response.

Less successful have been attempted improvements in poverty reduction, maternal and child malnutrition, and access to primary care. "The stark reality is that prevalence of malnutrition in Bangladesh is among the highest in the world. Nearly half of children have chronic malnutrition. Moreover, over a third the population (more than 47 million) live below the poverty line, and income equality is widening"*, says Professor Bhuiya.

Additionally, more needs to be done to address the poorly-equipped public health sector which, although free to the poor, faces a reported shortage of 800 000 doctors and nurses. They point out that every year 4-5 million people are pushed into poverty because they have to pay for health services directly, partly due to the rapid growth of the unregulated, low-quality, high-cost private sector.

"Arguably the most daunting challenge is the health of poor people living in urban areas", says Professor Chowdhury. "In the last 40 years, the proportion of the population living in urban areas has risen from around 5% to 28%. This is projected to grow to more than 50% by 2050 - roughly 100 million people - putting tremendous pressure on already inadequate water, sanitation, and primary health-care services."*

The authors conclude by setting out a plan to create a second generation of health-system innovations that will guide Bangladesh towards universal health coverage.

Series paper 1 - The Bangladesh paradox: exceptional health achievement despite economic poverty.

Series paper 2 - Harnessing pluralism for better health in Bangladesh.

Series paper 3 - Community-based approaches and partnerships: innovations in health-service delivery in Bangladesh.

Series paper 4 - Explaining equity gains in child survival in Bangladesh: scale, speed, and selectivity in health and development.

Series paper 5 - Reducing the health effect of natural disasters in Bangladesh.

Series paper 6 - Innovation for universal health coverage in Bangladesh: a call to action.