To explore your interest in epidemiology, visit the Web site of the Centers for Disease Control and Prevention (CDC, http://www.cdc.gov) to read about topics such as environmental health, vaccines and immunizations, and to read articles from the Emerging Infectious Diseases journal (http://wwwnc.cdc.gov/eid). It would also be helpful to read about past epidemics and how they were dealt with. A recent example is the story of the polio epidemic of the 20th century and Jonas Salk's and Albert Sabin's race to find a vaccine against it. A good book on the topic is Polio: An American Story, by David M. Oshinsky (New York: Oxford University Press, USA, 2006). Another frightening—and more recent—epidemic was the 2014 Ebola outbreak in West Africa. An excellent book on the topic is Ebola: The Natural and Human History of a Deadly Virus, by David Quammen (New York: W. W. Norton & Company, 2014). Finally, talking to an epidemiologist about his or her career will provide you with a wealth of information about the field.

Epidemiologists use research, statistical analysis, field investigations, and laboratory techniques to attempt to determine the cause of a disease, how it spreads, and what can be done to prevent and control it. They measure the incidence of a disease and relate it to characteristics of populations and environments. Many work on developing new methods or refining old ways of measuring and evaluating incidence of disease. 

Epidemiologists who study diseases in laboratories and in the field to help prevent future outbreaks are called research epidemiologists. Those who respond to outbreaks of disease—such as the Ebola virus—and try to stop them are known as applied epidemiologists. They typically work for state health agencies.

Epidemiologists' work is important to the medical community and to public health officials, who use their information to determine public health policies. Epidemiologists often develop and recommend public health policies using the research they have collected.

The field of epidemiology is complex, with multiple specializations. Infectious disease epidemiologists focus on diseases caused by bacteria and viruses, such as botulism, chicken pox, and Zika. Chronic disease epidemiologists study noninfectious diseases that can be genetic or lifestyle-induced, such as lung cancer, heart disease, and ulcers. Some epidemiologists have done work on rising teenage suicide rates and murders by guns because they are considered epidemics.

Environmental epidemiologists study connections between environmental exposure and disease. They have linked radon with lung cancer, found that interior house lead-based paint can cause lead poisoning in children, and discovered that dust from soybeans caused an asthma epidemic in Barcelona, Spain. Each state has its own head epidemiologist, who is usually part of the state's public health service. These state epidemiologists work closely with the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta. States are required by law to report certain diseases in their populations to the CDC on a regular basis. For example, states must report outbreaks of influenza or incidences of food poisoning to the CDC.

Some epidemiologist work as infection control specialists in hospitals and other health care and group facilities. These professionals work to prevent nosocomial infections (such as surgical site infections, multidrug-resistant tuberculosis, and the Hepatitis B virus). They also collect and analyze health data and train other health care workers regarding infection control practices.