Accessibility Factors Involved in HIV Spread (image) University of Florida Share Print E-Mail Caption The gradient of colors indicates the estimated travel time to the nearest city with a population of more than 500,000, with yellow at one extreme indicating short travel times and red at the other extreme indicating long travel times. The graphic explains accessibility factors affecting the spread of HIV from central to east Africa. The virus was circulating at stable levels in the urban centers of the Democratic Republic of Congo, but these centers were isolated. Once the virus reached east Africa, connectivity between population centers combined with better quality transportation networks and higher rates of human movement caused HIV to spread exponentially. Credit Andrew J. Tatem/University of Florida Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.