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The National Academies: What You Need To Know About Infectious Disease

What You Need To Know About Infectious Disease

An electron micrograph of an influenza virus, showing details of its structure.

Credit: Cynthia Goldsmith/CDC

Viruses

Viruses are tiny, ranging in size from about 20 to 400 nanometers in diameter. Billions can fit on the head of a pin. Some are rod shaped; others are round and 20 sided; and yet others have fanciful forms, with multisided “heads” and cylindrical “tails.”
Viruses are responsible for a wide range of diseases, including the common cold, measles, chicken pox, genital herpes, and influenza.
Viruses are simply packets of nucleic acid, either DNA or RNA, surrounded by a protein shell and sometimes fatty materials called lipids. Outside a living cell, a virus is a dormant particle, lacking the raw materials for reproduction. Only when it enters a host cell does it go into action, hijacking the cell’s metabolic machinery to produce copies of itself that may burst out of infected cells or simply bud off a cell membrane. This lack of self-sufficiency means that viruses cannot be grown in artificial media for scientific research or vaccine development; they can be grown only in living cells, fertilized eggstissue cultures, or bacteria.
 
Viruses are responsible for a wide range of diseases, including the common cold, measleschicken pox, genital herpes, and influenza. They also cause many of the emerging infectious diseases, among them AIDS, Ebola, and Zika.
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Disease Watchlist

What do you know about infectious disease?

Which of the following diseases is NOT caused by a virus?

  • Sorry, that’s incorrect.

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

  • Sorry, that’s incorrect.

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

  • Sorry, that’s incorrect.

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

  • Correct!

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

Infectious Disease Defined

Virus

An infectious agent that is only capable of replicating itself inside the living cells of other organisms.

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National Academies Press

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