the academic school year, offering free vaccines to students to prevent flu outbreaks. For those who are medically able to receive the vaccination, momentary discomfort and minor side effects are a small price to pay for protection against a potentially deadly virus.
Both of these cases—Sandra receiving treatment for the flu and Sandra receiving a vaccine—are clear examples of healthcare and medicine. However, they are also within the scope of public health.
What exactly is public health and how does it differ from medicine in general? As a rough guide, medicine deals with the interaction of a single doctor and patient: Sandra receiving care from her doctor for influenza. On the other hand, public health focuses on an entire population and asks what can be done to improve the health and prevent disease in mass. How can we inoculate a population to a disease, and track an outbreak as it develops?
How many patients do you need to treat before you are in the domain of public health? After all, developing a new cancer drug can save millions of lives, but we wouldn’t consider it public health. Conversely, an effective public health intervention may only impact a few hundred people. The distinction between the two isn’t a matter of numbers.
Furthermore, the choice of topic alone doesn’t determine if work is considered public health. Some areas of medicine fall almost entirely under the domain of public health, such as controlling environmental pollution to limit negative health outcomes or improving vehicle safety to prevent traffic fatalities. Other areas fall outside of public health research, such as new surgical or radiology techniques. But many domains touch both public health and traditional medicine, including drug overdoses, mental illness, and our example above: infectious disease and vaccinations.
What makes an area a public health topic isn’t the disease or ailment: it’s the types of interventions and goals.
Consider the vaccine example above. If Sandra had visited her doctor earlier in the semester, the physician might have recommended she receive her annual flu shot during her visit. This interaction isn’t in the domain of public health. Furthermore, the research that goes into developing the vaccine isn’t necessarily public health either. Her campus deciding to launch a vaccination campaign with the goal of reaching hundreds or thousands of students, or working with local clinics to ensure they distribute vaccine information—that is public health.
If what defines public health is a set of methods and goals, then what are they? This chapter provides an answer. We will outline the basic goals and principles of public health. Our goal is to provide basic fluency with the field to set the stage for understanding how social media can advance public health understanding.
Before we get into specifics, we should step back to consider the amazing success public health has had so far. Public health efforts have led to safer roads and cars to dramatically reduce traffic deaths, improved workplace safety, reduced pollutants to create safe drinking water, reduced infant mortality, dramatically reduced tobacco use to prevent lung cancer, reduced cavities through water fluoridation, improved our ability to control disease outbreaks, and nearly wiped out several infectious diseases with vaccines.2
Let’s consider the seasonal influenza vaccine as just one example. Many of us are accustomed to our annual flu shot, but it’s worth admiring this marvel of our modern public health system. We often forget just how unique it is to have a treatment that entirely prevents a disease from ever infecting a patient. After all, the first vaccine (for smallpox) was only invented at the turn of the 19th century. In the case of the seasonal flu shot, there are a number of challenging factors.
We’ll focus for a moment on the United States. First, for a variety of reasons, each season’s influenza strain requires its own vaccine. This means that researchers must develop a new vaccine each year. Second, in order to allow enough time to produce millions of doses of vaccines, decisions on what influenza strains should be included in the annual vaccine must be made many months before the start of flu season. Researchers make educated guesses based on currently circulating strains, as well as looking at countries in the southern hemisphere. Since these countries have winter during the U.S. summer, we can gain clues as to what strains may be circulating by looking at their flu season. As an aside, often times the reason that a flu shot is less effective is because unanticipated strains are circulating. Third, rapidly manufacturing safe and effective vaccines for the start of the flu season requires careful coordination between manufacturers and government agencies. Finally, vaccines rolling off the manufacturing line isn’t enough. Health organizations need to decide how many to order, and how to run vaccination campaigns. Should they run lots of advertising early in the season against a possible early seasonal peak, or should they run a longer campaign in anticipation of a late flu season? Will this season be mild, in which case they may not heavily advertise, or will it be a particularly severe season? It is a remarkable feat of the modern public health system that all of this comes together each year and results in tens of millions of Americans receiving a vaccine, preventing numerous infections, hospitalizations and deaths.
With a sense of amazement, let’s proceed to discussing the techniques and goals of public health.
2.1 THE PUBLIC HEALTH CYCLE
Broadly speaking, public health focuses on two distinct goals. First, to monitor and assess the health of a population, including the identification of health problems. Second, to craft health policies to address the identified health problems, including the task of ensuring the population has access to appropriate care. Rather than being distinct goals, they are intertwined. As policies and healthcare practices are revised, public health researchers must reassess the population to understand the effectiveness of the policies and practices and adjust accordingly.
These two goals are reflected in the public health cycle, which consists of ten different components [Harrell and Baker, 1994].3 Figure 2.1 illustrates how these components can be organized around three main activities.
• Assessment: monitoring the health of a population, and identifying and evaluating health issues.
• Policy development: education and development of community partnerships to come up with policies that address the results of assessment.
• Assurance: enforcing policies, providing access to care, and evaluating the results of the policies.
Social monitoring has a role to play in all three activities. It can be used to learn about a population, to help develop partnerships and debate policy, and to provide care. In disease prevention, we can measure infection prevalence in a population (assessment), network to create new partnerships with healthcare organizations to disseminate influenza information (policy development), and provide information on care, for example by sharing links to organizations providing vaccines (assurance). There are numerous examples of social media aiding health communication [Hawn, 2009, Moorhead et al., 2013] and various health interventions [Korda and Itani, 2013]. Many health agencies use social media for broadcasting information [Bartlett and Wurtz, 2015, Harris et al., 2013, Neiger et al., 2013], and doctors use social media to engage patients and the public [Lee et al., 2014b].
Figure 2.1: The three main stages of the public health cycle, along with their respective public health activities, as proposed by the Core Public Health Functions Steering Committee [Harrell and Baker, 1994].
As we said at the end of the previous chapter, this book will focus on assessment, which in the case of social media typically involves the passive monitoring of data to learn about health issues, and their prevalence, in a population. Social media is ideally suited for surveillance: it provides a constant stream of information on a population that can be monitored for topics of relevance to public health. Additionally, monitoring tasks is a more accessible type of research for computer scientists looking to work in public health. The main tools in this domain are data collection and analysis, as opposed to designing interventions or working with patients. That’s not to say that there aren’t many examples