But viruses show enormous variation in the shape of the molecules that make up their protein coat. These surface proteins determine the ability of the virus to latch on to the cells of its host and work its way inside - without the right key the virus stays locked outside. So the behaviour of a virus and particularly its ability to cause disease can often be predicted by an examination of its overall shape.
Dr Susan Lea is holder of the Royal Society's Dorothy Hodgkin Research Fellowship at the Laboratory of Molecular Biophysics at Oxford University.
She is using the well established technique of X-ray crystallography to investigate the surface structure of viruses. This virus is grown in a tissue culture, put into a chemical solution and isolated as solid crystals like grains of salt. Then it is bombarded with a beam of X-rays, where the energy is diffracted in a pattern which can be analysed to reveal the shape of the individual units that make up the crystal. She is currently studying a virus called echovirus 11 which can cause meningitis and occasionally paralysis, particularly in babies. It is not the most important virus of its type but it is far safer to handle in the laboratory than some of its cousins. These more dangerous strains produce diseases ranging from polio in humans to foot-and-mouth disease in cattle.
This group of viruses is among the most rapidly evolving organisms in nature.
Their protein coat is constantly changing to avoid being recognised and destroyed by the immune defences of their victims. However, says Dr Lea, "some things about them stay the same and I have been trying to understand why some things change while others stay constant. If we can determine how and why this happens we may be able to design new and better drugs which are targeted at those things we know that the virus cannot change".
If she succeeds Dr Lea would not be the first British woman to have made significant contributions to science using X-ray crystallography. Dorothy Hodgkin won the 1964 Nobel Prize for Chemistry after discovering the structure of penicillin, vitamin B12 and insulin using the technique. Meanwhile, Rosalind Franklin's work was vital in helping Crick and Watson unravel the DNA double helix, and the head of Susan's laboratory, Professor Louise Johnson, also has an international reputation in the field.
Dr Lea is fascinated by the challenge of her work and gave up a potentially much more lucrative career as a doctor after completing the preclinical stages of her medical degree. "Medicine is more about caring and remembering than a purely intellectual activity," she says. "I enjoy the level of creative thinking involved in research.
"In my field that does not end with the experiment - you have to really think about what the results mean."