102 Virus
Ivanovsky refused to believe that any living organism existed that was smaller than
bacteria and so concluded that his filters were defective and would not, in fact, catch small
bacteria. In disgust, he abandoned his project.
In 1898 Dutch botanist Martinus Beijerinick decided to try his luck at solving the mystery of tobacco mosaic disease. He repeated Ivanovsky’s experiment and got the same result. However, Beijerinick was quite willing to conclude that this experiment proved that
the causative agent was something new and unknown—something much smaller than bacteria. That was why it hadn’t been trapped in his filters. Beijerinick admitted that he did not
know what it was, but he claimed that his experiment proved that it existed and that it was
super-tiny. He named it a “virus,” the Latin word for poison.
While this discovery was intellectually interesting to some scientists, few cared about
a disease unique to tobacco plants. The notion of viruses received little attention from the
medical and scientific communities.
In 1899 German scientist Friedrich Loeffler conducted a similar test and concluded
that the agent responsible for foot-and-mouth disease was too tiny to be bacteria and so
must be another virus. Two years later, in 1901, American army surgeon Walter Reed exhausted his attempts to discover the cause for yellow fever that had killed so many American soldiers. Then he tested this mosquito-borne disease to see if whatever caused it was
small enough to be a virus. It was.
This discovery convinced the scientific world that viruses—1/1000 the size of even a
small bacterium—were the cause of many human ailments and had to be studied and treated
separately from bacteria. Ivanovsky and Beijerinick discovered viruses, but it took Walter
Reed to make the medical and scientific community pay attention.
Fun Facts: What’s the most common disease-causing virus? The common group of rhinoviruses, of which there are at least 180 types.
Rhinoviruses cause colds and are almost universal, affecting everyone
except for those living in the frozen wastes of Antarctica.
More to Explore
Fuffle, Cady. Viruses. New York: Gareth Stevens, 2003.
Gallo, Robert. Virus Hunting: Aids, Cancer, and the Human Retrovirus: A Story of
Scientific Discovery. New York: Basic Books, 1997.
Kanaly, Michael. Virus Clans: A Story of Evolution. New York: Penguin Books, 1999.
Mahy, Brian, ed. Concepts in Virology: From Ivanovsky to the Present. Abingdon,
England: Taylor & Francis, 1996.
van Iterson, G. Martinus Willem Beijerinck: His Life and Work. Washington, DC: Science Tech Publishers, 1995.