Researchers in the United States have discovered a link between the human cytomegalovirus and macular degeneration. This type of herpes virus can cause an infection of the eye which causes the production of vascular endothelial growth factor (VEGF) that regulates the formation of new blood vessels. The creation of these new blood vessels causes destruction of retinal tissue and leads to age-related macular degeneration. This discovery adds infections as a causal factor of macular degeneration along with genetics, high fat diet and smoking. The human cytomegalovirus is typically contracted during childhood and the majority of people have antibodies for it. The virus becomes latent but as a person ages, the immune system's function lessens and the virus can become active. Now that researchers have identified the virus as a cofactor in the development of AMD, they can look at creating an antiviral drug or modifying the genetics of the virus that generates VEGF production.