As if Nigeria didn’t have enough problems, a visitor from Liberia has just died of Ebola in its largest city, Lagos. The outbreak is the worst on record and shows no sign of slowing; so far it has been confined to Guinea, Liberia, and Sierra Leone for months. No longer. And the disease escaped in the most dreaded manner of all: by plane. Air travel, wonder though it is, means that Liberia effectively borders any country with an airport.Meanwhile, in Sierra Leone authorities are desperately trying to find an Ebola patient whose family took her by force from a hospital. The first victim in the country’s capital, Freetown, she is now at large in the city, which has one million residents. Doctors have long warned that the gravest dangers in this epidemic are fear and misinformation, the likely reasons her family sprang her from care. Panic makes people act dangerously: As we wrote recently, villagers in Sierra Leone set fire to a medical facility, thinking that it was spreading the disease instead of treating it.The disease is as deadly for the doctors as it is for the patients, as other tragic news reminds us. Sierra Leone’s top physician working to control the epidemic has been infected by the disease. Health care workers have been among the casualties of the disease all along; it is a testament to their bravery that so many continue working.Controlling this disease is as essential to the world as it is to West Africa. We are not untouchable by the scourge of the disease, and our distance from the outbreak is only somewhat reassuring.