Presented By

On Oct. 1, Texas health officials issued orders of quarantine to four people who’d had contact with Thomas Eric Duncan after he was diagnosed with Ebola. When Duncan died the morning of Oct. 8., those four remained quarantined. For many Americans, this raised the question of who has the legal authority to monitor their movement and human contact, restricting the liberty of presumably innocent people.

Under Section 361 of the Public Health Service Act, the Secretary of Health and Human Services is authorized to take measures to prevent the spread of communicable diseases between states and from outside the country. The CDC is responsible for carrying out these functions.

Isolation and quarantine can also be imposed by states under their police-power functions, but in the event that states’ powers aren’t sufficient to stem the spread of a disease, the federal government can step in.

Isolating the ill—or the potentially ill—under hospital authority is another way to contain bugs. On Wednesday, a hospital in Dallas isolated a patient with some Ebola symptoms until the test results come back showing whether or not he has the deadly virus. In September, an Indiana hospital placed a girl with Enterovirus, possibly the strain known as EV-D68, in isolation. This flu-like illness has infected 664 people in 45 states since mid-August, which is why doctors recommend the sick stay home from school and work – a form of self-isolation.

By definition, isolation separates contagious patients from the healthy whereas quarantine restricts healthy people who may have been exposed to a communicable disease. Both measures have been used throughout history, though the first formal system dates back some 700 years ago, when the city of Venice mandated a 40-day quarantine for incoming ships. The idea was to detain cargoes and individuals to ensure no one was carrying the plague onto its shores.

Here’s a closer look at the history of germ containment and how the two viruses – Ebola and EV-D68 – compare. (When viewing graphic: To zoom in, hover your mouse over the graphic. To scroll down, move your mouse over to the right, near the scroll bar in your browser. On a mobile device, turn sideways and keep to the right when swiping down.)

Graphic by Heather Jones for TIME

More Must-Reads From TIME

Write to Tessa Berenson at

You May Also Like