In March, Ebola was reported in Guinea and neighboring Liberia, killing 93 people out of 151 suspected cases in the worst outbreak in seven years. While previous epidemics have affected larger populations, what’s unusual this time is how the disease has spread. Originating in small towns in southeast Guinea, the virus traveled 660 kilometers (410 miles) to the coastal capital of Conakry. Earlier outbreaks have been in remote locations. The spread of the disease is fueled by poor health infrastructure and hygiene practices. Western Africa has an acute shortage of doctors; Guinea has just 0.1 physicians per 1,000 people, among the lowest ratios in the world. International aid groups such as Doctors Without Borders sent specialist teams with biohazard suits to set up isolation units and contain the outbreak. Ebola jumps to humans from infected animals that live in the rainforest through contact with blood and other secretions from chimpanzees, gorillas, bats and other species. It spreads among humans the same way. Sick people begin to erupt with symptoms two to 21 days after exposure, leaving health-care workers and family members the most at risk. To prevent the disease from spreading, Guinea has forbidden the sale and eating of bats. Senegal closed its southern border with Guinea and governments around the world are on high alert.