About 36,000 people die from flu-related complications each year in the United States. More than 200,000 are hospitalized.

About 36,000 people die from flu-related complications each year in the United States. More than 200,000 are hospitalized.

Most infectious diseases are impacted by changes in the environment. Malaria, dengue, and viral encephalitis infections, for example, are highly sensitive to environmental changes.

In syndromic surveillance, all of the above are used in addition to other patterns that suggest an outbreak. Despite the emergence of this innovative surveillance method, most surveillance still depends on tracking reported infections. 

In syndromic surveillance, all of the above are used in addition to other patterns that suggest an outbreak. Despite the emergence of this innovative surveillance method, most surveillance still depends on tracking reported infections. 

In syndromic surveillance, all of the above are used in addition to other patterns that suggest an outbreak. Despite the emergence of this innovative surveillance method, most surveillance still depends on tracking reported infections. 

Scientists predict that rising average temperatures in some regions—a result of climate change—will change the transmission dynamics and geographic range of cholera, malaria, dengue fever, and tick-borne diseases.

The 2009 “swine flu” pandemic starkly illustrated the impact of globalization and air travel on the movement of infectious diseases—with the infection spreading to 30 countries within six weeks and to more than 190 countries and territories within months.

The 2009 “swine flu” pandemic starkly illustrated the impact of globalization and air travel on the movement of infectious diseases—with the infection spreading to 30 countries within six weeks and to more than 190 countries and territories within months.

In 2008, more than 33 million people worldwide were infected with HIV (human immunodeficiency virus). In that same year, an estimated 2 million people died from AIDS (acquired immunodeficiency syndrome), the final stage of HIV infection.

In 2008, more than 33 million people worldwide were infected with HIV (human immunodeficiency virus). In that same year, an estimated 2 million people died from AIDS (acquired immunodeficiency syndrome), the final stage of HIV infection.

Today there are more antiviral drugs available for HIV than for any other viral disease, transforming an infection that was once considered a death sentence into a manageable chronic condition.

Today there are more antiviral drugs available for HIV than for any other viral disease, transforming an infection that was once considered a death sentence into a manageable chronic condition.

Today there are more antiviral drugs available for HIV than for any other viral disease, transforming an infection that was once considered a death sentence into a manageable chronic condition.

Bacteria are 10 to 100 times larger than viruses.

Since the beginning of the 20th century the number of people in the world has more than quadrupled—from 1.6 billion to nearly 7 billion—and world population is expected to rise to well over 9 billion by 2050.

Since the beginning of the 20th century the number of people in the world has more than quadrupled—from 1.6 billion to nearly 7 billion—and world population is expected to rise to well over 9 billion by 2050.