The Worst Outbreaks in U.S. History

An epidemic is definedTrusted Source by the Centers of Disease Control and Prevention (CDC) as a sudden increase in the number of cases of an infectious disease within a community or geographic area during a specific time period.

A spike in the number of cases of the same illness in an area beyond what health officials expect to see is an outbreak. The terms may be used interchangeably, though epidemics are often considered more widespread.

Over the years, many outbreaks of infectious diseases have occurred and spread across the United States.

1633-1634: Smallpox from European settlers

Smallpox came to North America in the 1600s. Symptoms included high fever, chills, severe back pain, and rashes. It began in the Northeast and the Native American population was ravaged by it as it spread to the west.

In 1721, more than 6,000 cases were reported out of a Boston population of 11,000. Around 850 people died from the disease.

In 1770, Edward Jenner developed a vaccine from cow pox. It helps the body become immune to smallpox without causing the disease.

Now: After a large vaccination initiative in 1972, smallpox is gone from the United States. In fact, vaccines are no longer necessary.

1793: Yellow fever from the Caribbean

One humid summer, refugees fleeing a yellow fever epidemic in the Caribbean Islands sailed into Philadelphia, carrying the virus with them.

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