A Living Chemical

In 2000, James Hogle (Harvard University) and colleagues used an electron microscope and X-ray crystallography to produce the first three-dimensional images of poliovirus.
David Belnap, biochemist, 2000

Poliomyelitis is caused by a poliovirus. Viruses are particles of either RNA or DNA, and are neither living nor dead. They cannot do anything until they find an appropriate cell whose internal mechanism they can commandeer to start reproducing themselves.

  • Karl Landsteiner and Erwin Popper discovered poliovirus in 1908 by proving that it was not a bacterium that caused the paralysis, but a much smaller entity—a virus.
  • Viruses are the smallest and simplest infectious agents known… so far.
  • Viruses are not cells, but have an attraction (tropism) for receptors on certain cells.
  • In addition to polio, RNA viruses include HIV, influenza A, the common cold, hepatitis A and C, yellow fever, rabies, mumps, and measles.

Copy of the first image of poliovirus taken with an electron microscope, 1953

The electron microscope, invented in 1931, allowed researchers to see viruses for the first time. Since it uses a beam of high-energy electrons (which have short wave lengths), an electron microscope is capable of much greater magnifications than a conventional light microscope.
Courtesy of David Sarnoff Library


Virology, the study of viruses, started in the 1890s as an offshoot of bacteriology. Viruses were defined primarily by their small size. Size was determined by the virus's ability to pass through a filter such as this porcelain one, and by its invisibility under a light microscope.

A white porcelain filter on top of a chemistry supply catalog from the late 19th century.

A porcelain Chamberland filter such as this, would have been used to trap bacteria yet allow viruses to pass through.

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If the ability to replicate is one of life’s attributes, then polio is a chemical with a life cycle…. Viruses are ‘living’ chemicals. They have structural uniformity, like crystals, but can only self-replicate inside living cells. Poliovirus is made up of carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur: C332,662, H492,388, N98,245, O131,196, P7,500, S2,340. From these elements, the virus forms its RNA (ribonucleic acid) genes, and its protective protein coat.
Jeronimo Cello, Aniko V. Paul, Eckard Wimmer, creators of the synthesized poliovirus, 2002

Picture of poliovirus. The poliovirus is extremely small, about 50 nm (nanometer = one-billionth of a meter)
Courtesy of David Belnap and James Hogle

Compared to a bacterium, poliovirus is like a person standing next to the Statue of Liberty. Visitors here in the crown of the Statue.
© Diana Walker, photographer

Most viruses are far too tiny to be seen in an ordinary high-powered microscope, except perhaps as a minute spot of light against a dark background.
Francis Crick, co-discoverer of the double-helix structure of DNA, 1988

Poliomyelitis: Inflammation of the gray matter of the spinal cord. P., acute anterior, acute inflammation of the anterior horns of the gray matter of the spinal cord, leading to a destruction of the large multipolar cells of these horns. It is most common in children, coming on during the period of the first dentition and producing a paralysis of certain muscle groups or of an entire limb.
Gould’s Illustrated Medical Dictionary, 1895

Poliomyelitis: An inflammatory process involving the gray matter of the cord. Acute anterior p., inflammation of the anterior cornua of the spinal cord; an acute infectious disease caused by the poliomyelitis virus and marked by fever, pains, and gastroenteric disturbances, followed by a flaccid paralysis of one or more muscular groups, and later by atrophy.
Stedman’s Medical Dictionary, 1995