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.

Strep throat is a bacterial infection. Hookworm is caused by a parasite and chickenpox and influenza are both caused by viruses.

Strep throat is a bacterial infection. Hookworm is caused by a parasite and chickenpox and influenza are both caused by viruses.

Strep throat is a bacterial infection. Hookworm is caused by a parasite and chickenpox and influenza are both caused by viruses.

The clearing and settlement of tropical rainforests has exposed woodcutters, farmers, and ecotourists to new vector-borne diseases.

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.

Bacteria are 10 to 100 times larger than viruses.

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.

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.

Life-saving vaccines and medications aren’t distributed equitably around the world; for each child who dies from pneumonia in an industrialized country, more than 2,000 children die from the infection in developing countries.

Life-saving vaccines and medications aren’t distributed equitably around the world; for each child who dies from pneumonia in an industrialized country, more than 2,000 children die from the infection in developing countries.

Life-saving vaccines and medications aren’t distributed equitably around the world; for each child who dies from pneumonia in an industrialized country, more than 2,000 children die from the infection in developing countries.

White blood cells are not a type of infectious agent. Part of the immune system, white blood cells fight infection rather than cause it. 

White blood cells are not a type of infectious agent. Part of the immune system, white blood cells fight infection rather than cause it. 

White blood cells are not a type of infectious agent. Part of the immune system, white blood cells fight infection rather than cause it.