Why are some diseases deadlier than others? It’s a difficult balance for pathogens: staying latent and harmless in their host means they don’t risk killing off potential victims, but they reproduce slowly. Recent research has shown that the amount their hosts move around also matters. Here two viruses, marked green and blue, are infecting a lawn of cells. The cells on the left were kept still so the viruses haven’t spread far, but the others were disturbed, so the viruses have infected wider areas. It was found that when hosts don’t move about, deadlier viruses initially predominate but they soon kill so many nearby hosts that the less virulent viruses became more common. However, when there’s lots of mixing, spreading faster is an advantage so the deadlier viruses win out. This helps us understand how diseases change as they move across the globe.
Written by Esther Redhouse White
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