Worldwide, 884 million people do not have access to an adequate water supply, and about three times that number lack basic sanitation services. An estimated 2 million deaths a year can be attributed to unsafe water supplies.

Worldwide, 884 million people do not have access to an adequate water supply, and about three times that number lack basic sanitation services. An estimated 2 million deaths a year can be attributed to unsafe water supplies.

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.

The United States imports more than 80 percent of its fish and seafood. About 20 percent of its fresh vegetables and 50 percent of its fresh fruits are imported. As wealthy nations demand such foods year-round, the increasing reliance on producers abroad means that food may be contaminated during harvesting, storage, processing, and transport—long before it reaches overseas markets.    

The United States imports more than 80 percent of its fish and seafood. About 20 percent of its fresh vegetables and 50 percent of its fresh fruits are imported. As wealthy nations demand such foods year-round, the increasing reliance on producers abroad means that food may be contaminated during harvesting, storage, processing, and transport—long before it reaches overseas markets.    

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.

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.

Antibiotics only work on bacterial infections, not viral infections such as influenza and the common cold. In fact, inappropriate use and overuse of antibiotics contributes to the emergence of drug-resistant bacteria. 

More than half of the known pathogens that infect people have come from animals. Of the 37 new infectious diseases identified in just the past 30 years, two-thirds sprang from animals.

More than half of the known pathogens that infect people have come from animals. Of the 37 new infectious diseases identified in just the past 30 years, two-thirds sprang from animals.

Although there are treatments available in the form of antivirals, we still currently lack a vaccine for HIV.

Although there are treatments available in the form of antivirals, we still currently lack a vaccine for HIV.

Although there are treatments available in the form of antivirals, we still currently lack a vaccine for HIV.