The Physics
Factbook
An encyclopedia of scientific essays

Diameter of a Virus

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Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Otto, James and Albert Towle. Modern Biology. New York: Holt, Rinehart & Winston, 1985. "15 nm to 200 nm" 15–200 nm
Marx, Jean L. "Virus." The Encyclopedia Americana International Edition. vol. 28. New York: Grolier, 1991: 172. "20 to 400 nm" 20–400 nm
Jackson, George Gee. "The Common Cold." Cecil's Textbook of Medicine. Philadelphia: Saunders, 1970: 359. "5 µ to 50 µ. The common cold or Acute Coryza."
[This measurement is the size sneeze droplets.]
n/a
Nourse, Alane. Viruses. New York: Franklin Watts, 1976. "(1.0 × 10−6)/3 µ to (3.0 × 10−7)/35 µ" 8.6–330 nm
Hale, W. G. & J. P. Margham. Harper Collins Dictionary of Biology. New York: Harper Collins, 1991. "0.025 µm to 0.25 µm" 25–250 nm

Viruses are some of the smallest non-cellular organisms known to man. These simple parasites are composed of nucleic acid and a protein coat. They are extremely small -- only with an electron microscope can they be seen. Most viruses are smaller than eukaryotic cells and even bacteria. Methods of studying viruses have changed over time. One method is to place virus particles in a solution of bacteria then wait until the virus multiplies and takes over.

After searching through various sources, I found a length ranging from 1.5 × 10−8 m to 5.0 × 10−5 M. There could be various reasons for the contrast in information, including the sheer number of viruses. There are hundreds of viruses that are responsible for the common cold alone. With so many, recorded sizes may vary according to the variety.

I accidentally looked up the size of sneeze droplets that contain viruses for my "technical source", but the measurement is still interesting.

My measurements were in microns and nanometers, so I converted the values to meters using the reference table from our text. Values in microns were multiplied by 10−6 and those in nanometers were multiplied by 10−9.

Michael Nicholas -- 1996

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Randerson, James. "Massive virus discovered in water tower." New Scientist. 27 March 2003. "Although the new virus is a thousand times smaller than a pinhead, its girth of 400 nanometres makes it a mammoth in the microbial world. Most viruses measure between 10 and 100 nanometres, and the newcomer is even bigger than some bacteria." 10–100 nm
(typical)
400 nm
(maximum)

Editor's Supplement -- 2003