Phones like Hussein’s hold great potential to improve the way health services are delivered. One major study demonstrating as much was started five years ago by Richard Lester, a Canadian infectious-disease specialist. After arriving in Kenya for a research fellowship, noting the ubiquity of mobile phones, and recognizing that the country has only one doctor for each 6,000 citizens, Lester and his team developed a communication link with HIV-positive patients at three health centers, asking them weekly by text message whether they needed any assistance with their antiretroviral drugs (ARVs). Once 500 people were participating, Lester conducted a clinical trial. The results, published in 2010, showed not only that a higher percentage of those receiving the reminders said they took their drugs regularly, but also that viral loads were suppressed in 57 percent of them, compared with only 48 percent of the control group. Today he estimates that expanding that system to all 410,000 Kenyans on ARVs would suppress HIV in 36,000 people, saving $17.4 million in health-care costs by averting the onset of AIDS or making more expensive drugs unnecessary.