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.

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.

Someone in the world is newly infected with tuberculosis (TB) every second. In 2008 there were an estimated 9.4 million new cases of tuberculosis and 1.8 million deaths.The vast majority of TB deaths are in the developing world, and more than half of all deaths occur in Asia.

Someone in the world is newly infected with tuberculosis (TB) every second. In 2008 there were an estimated 9.4 million new cases of tuberculosis and 1.8 million deaths.The vast majority of TB deaths are in the developing world, and more than half of all deaths occur in Asia.

All of the above can help prevent infectious disease. Other behaviors, such as exercising caution around wild and unfamiliar domestic animals, avoiding insect bites, practicing safe sex, and being vigilant about disease threats while traveling abroad, can also reduce the risk of infection.

All of the above can help prevent infectious disease. Other behaviors, such as exercising caution around wild and unfamiliar domestic animals, avoiding insect bites, practicing safe sex, and being vigilant about disease threats while traveling abroad, can also reduce the risk of infection.

All of the above can help prevent infectious disease. Other behaviors, such as exercising caution around wild and unfamiliar domestic animals, avoiding insect bites, practicing safe sex, and being vigilant about disease threats while traveling abroad, can also reduce the risk of 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.

Strep throat is a bacterial infection that can be treated with antibiotics. The common cold and influenza are both viral infections, which do not respond to antibiotics. Antivirals may be prescribed instead.

Strep throat is a bacterial infection that can be treated with antibiotics. The common cold and influenza are both viral infections, which do not respond to antibiotics. Antivirals may be prescribed instead.

Strep throat is a bacterial infection that can be treated with antibiotics. The common cold and influenza are both viral infections, which do not respond to antibiotics. Antivirals may be prescribed instead.

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

Tuberculosis is caused by a bacterial infection. Chicken pox, the common cold, and influenza are all caused by viral infections.

Tuberculosis is caused by a bacterial infection. Chicken pox, the common cold, and influenza are all caused by viral infections.

Tuberculosis is caused by a bacterial infection. Chicken pox, the common cold, and influenza are all caused by viral infections.

Lower respiratory tract infections (including pneumonia) kill more children worldwide than any other infectious disease. Together these diseases are the five leading causes of infectious disease worldwide, accounting for nearly one-fifth of all deaths.

Lower respiratory tract infections (including pneumonia) kill more children worldwide than any other infectious disease. Together these diseases are the five leading causes of infectious disease worldwide, accounting for nearly one-fifth of all deaths.

Lower respiratory tract infections (including pneumonia) kill more children worldwide than any other infectious disease. Together these diseases are the five leading causes of infectious disease worldwide, accounting for nearly one-fifth of all deaths.

Lower respiratory tract infections (including pneumonia) kill more children worldwide than any other infectious disease. Together these diseases are the five leading causes of infectious disease worldwide, accounting for nearly one-fifth of all deaths.