In January 1925, winter settled over Alaska like an iron blanket. There were snowdrifts, high winds, and blizzards. Temperatures often dropped as low as thirty or forty degrees below zero. Once winter came, the people of Nome were totally cut off from the outside world. But that January of 1925, a crisis came to the small, isolated city, and even the toughest citizens knew they needed help—winter or not. The crisis was a diphtheria epidemic. An epidemic is the very quick spread of a disease to a large number of people. Epidemics can be very difficult to stop, even under good conditions. And the conditions in Nome were far from good. Diphtheria, which often struck children in the past, begins with a flu-like fever and a sore throat. The disease quickly progresses to a very serious stage and is often deadly. Today children are given a simple injection to prevent them from catching the disease, but in 1925 the only cure was an antitoxin serum. In Nome, there was just enough serum to treat a few infected people.