information:extraction, information:filtering, information:classification
Changing focal areas and expanding scope

With the onset of the epidemiological transition and as the prevalence of infectious diseases decreased through the 20th century, public health began to put more focus on chronic diseases such as cancer and heart disease. Previous efforts in many developed countries had already led to dramatic reductions in the infant mortality rate using preventive methods. In Britain, the infant mortality rate fell from over 15% in 1870 to 7% by 1930.

A major public health concern in developing countries is poor maternal and child health, exacerbated by malnutrition and poverty. The WHO reports that a lack of exclusive breastfeeding during the first six months of life contributes to over a million avoidable child deaths each year.

Public health surveillance has led to the identification and prioritization of many public health issues facing the world today, including HIV/AIDS, diabetes, waterborne diseases, zoonotic diseases, and antibiotic resistance leading to the reemergence of infectious diseases such as tuberculosis. Antibiotic resistance, also known as drug resistance, was the theme of World Health Day 2011.

For example, the WHO reports that at least 220 million people worldwide have diabetes. Its incidence is increasing rapidly, and it is projected that the number of diabetes deaths will double by 2030. In a June 2010 editorial in the medical journal The Lancet, the authors opined that "The fact that type 2 diabetes, a largely preventable disorder, has reached epidemic proportion is a public health humiliation." The risk of type 2 diabetes is closely linked with the growing problem of obesity. The WHO's latest estimates as of June 2016 highlighted that globally approximately 1.9 billion adults were overweight in 2014, and 41 million children under the age of five were overweight in 2014. Once considered a problem in high-income countries, it is now on the rise in low-income countries, especially in urban settings.

Many public health programs are increasingly dedicating attention and resources to the issue of obesity, with objectives to address the underlying causes including healthy diet and physical exercise. The National Institute for Health and Care Research (NIHR) has published a review of research on what local authorities can do to tackle obesity. The review covers interventions in the food environment (what people buy and eat), the built and natural environments, schools, and the community, as well as those focussing on active travel, leisure services and public sports, weight management programmes, and system-wide approaches.

Health inequalities, driven by the social determinants of health, are also a growing area of concern in public health. A central challenge to securing health equity is that the same social structures that contribute to health inequities also operate and are reproduced by public health organizations. In other words, public health organizations have evolved to better meet the needs of some groups more than others. The result is often that those most in need of preventative interventions are least likely to receive them and interventions can actually aggravate inequities as they are often inadvertently tailored to the needs of the normative group. Identifying bias within public health research and practice is essential to ensuring public health efforts mitigate and don't aggravate health inequities.