Growing evidence does suggest that infections are behind many chronic diseases once thought to be caused by genetic, environmental, or lifestyle factors, including peptic ulcers and cervical, liver, and gastric cancers.

About ten trillion microbes live in the human gastrointestinal tract. They are essential for proper digestion and absorption of nutrients.

About ten trillion microbes live in the human gastrointestinal tract. They are essential for proper digestion and absorption of nutrients.

About ten trillion microbes live in the human gastrointestinal tract. They are essential for proper digestion and absorption of nutrients.

Almost 70% of all the antibiotics produced in the United States is added to animal feeds—not to fend off disease but to boost growth. These non-therapeutic uses of antibiotics are a perfect way to cultivate microbes that are resistant to antibiotics.

Almost 70% of all the antibiotics produced in the United States is added to animal feeds—not to fend off disease but to boost growth. These non-therapeutic uses of antibiotics are a perfect way to cultivate microbes that are resistant to antibiotics.

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

All of the above are urgently needed in developing nations. A major barrier to achieving these improvements is the underlying weakness of health systems in resource-poor countries, including a shortage of health workers and a lack of disease surveillance programs.

All of the above are urgently needed in developing nations. A major barrier to achieving these improvements is the underlying weakness of health systems in resource-poor countries, including a shortage of health workers and a lack of disease surveillance programs.

All of the above are urgently needed in developing nations. A major barrier to achieving these improvements is the underlying weakness of health systems in resource-poor countries, including a shortage of health workers and a lack of disease surveillance programs.

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.

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.

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.

The gap in life expectancy between the richest and poorest countries now exceeds 40 years.

The gap in life expectancy between the richest and poorest countries now exceeds 40 years.

The gap in life expectancy between the richest and poorest countries now exceeds 40 years.