Like other viruses, bean common mosaic virus interferes with genetic signalling within the plant. Leaves that are distorted by the virus cannot function normally, so plants stop gaining size and may produce dense clusters of infertile flowers.
Do not save seeds from plants that show symptoms of viral infection, because the virus can be carried within the seed. Many bean varieties are resistant to common mosaic virus; resistant varieties may show slight symptoms, and then outgrow the problem. Measures that reduce aphid populations will cut the risk of this and other viral diseases in the garden. Grow plenty of nectar-producing flowers to attract aphid predators including ladybirds, lacewings and hoverflies.
Infected plants may make a slight recovery, but they will not be good producers. To keep the problem from spreading, pull up infected plants and compost them. Dispose of any unused seeds, because it is possible the seeds were infected with the virus.