On Sept. 26, 1951, the U.S. Centers for Disease Control and Prevention (CDC) established the Epidemic Intelligence Service (EIS) to protect America from the spread of disease and other global health threats, and to build a corps of trained epidemiologists who can be deployed immediately for any contingency, including chemical or biological warfare.

The EIS is a program administered by the Centers for Disease Control and Prevention (CDC) as a two-year postgraduate program of service and on-the-job training for health professionals interested in the practice of epidemiology. Each year, 70–80 people are selected and assigned to CDC or state and local health department positions. EIS officers conduct epidemiologic investigations, research and public health surveillance nationally and internationally. Since 1951, more than 3,500 EIS officers have responded to requests for epidemiologic assistance within the United States. These EIS Officers serve on the public health protection frontlines.

The term “shoe-leather epidemiology” is used to describe the investigation style epidemiologists conduct. Shoe leather refers to old style detectives who walked the streets wearing out shoes while solving cases. Similarly, EIS Officers have to engage in detailed, one-on-one conversations with each new patient and their loved ones and acquaintances to solve the mystery of a disease and the source of an outbreak.

Today, most people are familiar with diseases like Ebola, Zika and Norovirus. You name a disease, and disease detectives have chased it. During the Ebola epidemic, CDC deployed 156 of 158 EIS officers. These officers were deployed to 17 countries, eight states and CDC’s Emergency Operations Center. With Zika virus, officers are continuing to be deployed as the current outbreak continues.

The CDC Foundation helps the public health system—state and local health departments, community organizations, international partners and the Centers for Disease Control and Prevention (CDC)—save and improve lives by unleashing the power of partnerships to protect communities in America and across the globe.