Diphtheria has been virtually eradicated in the United States because of a vaccine, which was introduced in the 1920s. Before that time, the United States had 100 to 200 cases per 100,000 people. The disease is still a problem in developing countries. Two types of diphtheria exist, respiratory and cutaneous. The former is more serious, and death results in about 10% of those cases. The disease is spread through respiratory droplets and from contaminated objects or food. The incubation period for the disease is usually 2 to 5 days. Develop a model for respiratory diphtheria (NCBI).