However, over the full years of vaccine development, scientists possess learnt that the road to locating a virus of suitable power is fraught with challenges. This hurdle is certainly compounded by the complexity of the dengue virus. Despite the fact that there are just four different serotypes, the fairly high prices of mutation continuously means the virus evolve, and this plays a part in the fantastic diversity of the dengue viruses circulating globally. Furthermore, in some cases, the immune response developed following infection by among the four dengue viruses appears to increase the threat of severe dengue when the same individual is infected with any of the remaining three viruses.Patients were followed after graft surgery treatment to examine the gain access to site monthly; to record access-related problems, adverse medication reactions, and hospitalizations; also to assess adherence to the analysis medication regimen through a pill count. Follow-up was continued until 1 month following the occurrence of the principal outcome. Blood-flow prices at the access site were measured every month after the individual started hemodialysis, by using the ultrasound indicator dilution technique ,15 which provided a uniform studywide approach to detect a reduction in the blood-flow price indicative of stenosis before it resulted in thrombosis.14 Outcomes The principal outcome was loss of primary unassisted graft patency , thought as the initial occurrence of graft thrombosis, an access treatment performed to improve a stenosis of 50 percent or more of the diameter of the adjacent normal vessel, or other surgical modification of the graft .