The world breathes a lot easier as Dr Kent Brantly's breathing improves. The American missionary worker, who contracted Ebola in Liberia, was sure he would die. He knew the symptoms too well - rashes, laboured breathing. He had seen too many die before him to get it wrong.
He hadn't heard of ZMapp. Neither had the world.
Frozen vials of ZMapp were flown from the US to Liberia, where Brantly and fellow health worker Nancy Writebol were administered the new drug. Both have since shown improvement.
ZMapp hasn't been tried on humans before and it's too early to say with certainty that it works. Still, after weeks of terrifying news of an unstoppable disease that has killed more people in four countries than severe acute respiratory syndrome (Sars) did in five continents, ZMapp gives hope.
But it also raises some uncomfortable questions. If there was an outside chance that this "secret serum" could work, why was it kept secret? Why hadn't it been tried on the nearly 900 Africans who have died of the disease? Why did two American health workers have to fall ill for it to be brought out of the freezer?
The latest outbreak of Ebola in West Africa began in February. ZMapp, The Washington Post tells us, was first identified as a drug candidate in January. Have we wasted time by sitting on the drug?
"The risk [of using ZMapp on the two health workers] was less than the potential benefit," a senior American health official told the paper. Could the same cost-benefit analysis have been done for African patients?
"Experts: Ebola Vaccine At Least 50 White People Away", read a recent headline in spoof paper The Onion. Many a true word is spoken in jest, but here the truth is far more complicated. "As doctors, trying an untested drug on patients is a very difficult choice since our first priority is to do no harm," says Doctors Without Borders (also called MSF), on the ethical and practical problems of testing a drug in the middle of an epidemic.
This is where we need to look at things afresh. If death is inevitable and an untested drug could be the way out, why not? What better place to run a clinical trial than during a deadly epidemic, and for what better reason?