IN late May, a woman was admitted to the Kenema Government Hospital’s maternity ward in Sierra Leone after a bloody miscarriage. Augustine Goba, director of the hospital’s diagnostic laboratory and my longtime collaborator, ran a series of sensitive molecular tests and detected the first case of Ebola infection in the hospital, and one of the first confirmed cases in the country. Dr. Sheik Humarr Khan, Sierra Leone’s leading virologist, and other medical staff members isolated the patient and wore gloves, gowns and masks while treating her. She survived and made a full recovery, and no one else was infected.

Had this patient been one of the first cases of Ebola in West Africa, the hospital’s rapid diagnosis and expert handling might have helped control the outbreak quickly. But by May, the epidemic had already been spreading for six months, with hundreds of cases in neighboring Guinea and Liberia. When the hospital’s outreach team traveled to the patient’s village, they found that 14 people had already been infected, with what turned out to be two distinct versions of the virus. With each week, the number of confirmed cases in Sierra Leone grew, to 31, then 92, then 147, until the virus emerged in nearly every district of the country.

Kenema was well positioned to detect and treat Ebola because of its experience combating another deadly virus, Lassa, a project I started working on in 2008. As the hospital’s reputation for treating Lassa fever spread, more patients with unexplained fevers began to travel there. Rapid diagnosis of more people not only helped treat individual patients, but it could also uncover other unexpected pathogens hiding in the population, thus warning of outbreaks before they became global threats. Just weeks before Ebola entered Sierra Leone, Dr. Khan and I joined colleagues from around the world in Nigeria to inaugurate the African Center of Excellence for Genomics of Infectious Disease, a new venture that would enable monitoring of dangerous microbes across West Africa.

The Ebola outbreak put our plans on hold. Soon after Dr. Khan returned to Kenema, the hospital became overwhelmed. He and the nurses were treating up to 80 patients at a time, working 16-hour days. In the United States, my colleagues and I struggled to get aid and novel treatments to them, while we worked on sequencing the virus’s genome. Help did not come in time. While drafting a paper on the viral samples from Kenema, we began receiving devastating messages. Seven members of our team had become infected with Ebola. The constant flow of severely ill patients made it impossible for hospital staff members to protect themselves. Over the next few months, around 40 contracted the disease, including Mbalu Fonnie, a head nurse, who had worked there for 25 years, and Dr. Khan. By the middle of the summer, they were both dead.