Smallpox cannot be found naturally in the wild. Smallpox was officially declared eradicated from the globe in 1980, after an 11-year WHO vaccination campaign—the first human disease to be eliminated as a naturally spread contagion. Today, the virus remains only in laboratory stockpiles.

Smallpox cannot be found naturally in the wild. Smallpox was officially declared eradicated from the globe in 1980, after an 11-year WHO vaccination campaign—the first human disease to be eliminated as a naturally spread contagion. Today, the virus remains only in laboratory stockpiles.

An estimated 1.8 million airline passengers cross international borders daily, creating routes by which human infections can radiate around the world within hours.

An estimated 1.8 million airline passengers cross international borders daily, creating routes by which human infections can radiate around the world within hours.

The 1918 influenza pandemic is estimated to have killed between 50 million and 100 million people worldwide. Many of those deaths were due to the effects of pneumococcal pneumonia, a secondary complication of flu for which no antibiotics existed in 1918.

The 1918 influenza pandemic is estimated to have killed between 50 million and 100 million people worldwide. Many of those deaths were due to the effects of pneumococcal pneumonia, a secondary complication of flu for which no antibiotics existed in 1918.

“Antibiotic resistance” refers to the ability of bacteria to resist the effects of an antibiotic. Antibiotic resistance occurs when bacteria undergo a genetic change that reduces or eliminates the effectiveness of drugs or other agents designed to cure or prevent infection.

“Antibiotic resistance” refers to the ability of bacteria to resist the effects of an antibiotic. Antibiotic resistance occurs when bacteria undergo a genetic change that reduces or eliminates the effectiveness of drugs or other agents designed to cure or prevent infection.

Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply. Disease follows when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear.

Not all microbes are harmful to humans. In fact, many of them protect us, helping our bodies function properly and competing with harmful organisms in an eternal contest for habitable space in or on our bodies. Although the microorganisms that cause disease often receive more attention, most microorganisms do not cause illness.

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.

Washing with regular soap is considered the most important way to prevent disease transmission. Routine consumer use of residue-producing antibacterial products has no added benefit and may actually contribute to antibiotic resistance.

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.