Comparison: Sizes of Organisms

There are vast differences in size between the various infectious organisms. However, an organism’s size does not determine the severity of the disease it causes. A microscopic virus can lead to a life-threatening illness, and a tapeworm 6 m (20 ft) long may cause only mild symptoms.

Relative dimensions of organisms

Worms are the largest disease-causing organisms. In this diagram, each successive picture after worms represents a 100-fold magnification. The smallest disease-causing organisms are the viruses.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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