Smallpox

This 1969 photograph depicted a Dekina, Nigerian male smallpox sufferer, and revealed the maculopapular rash dispersed over the victims face, which displayed numerous coalescent lesions; lesions were also visible on this patient's arms and chest.
Dekina, Nigerian male smallpox sufferer
This 1969 photograph was taken in Dekina, Nigeria, and showed the arm and leg of a smallpox patient with a heavy concentration of lesions. Note that lesions on the leg are almost confluent in appearance.
Arm and leg of a smallpox patient
This 1975 image of a small child who'd been stricken with smallpox was taken by Dr. Stan Foster, EIS, Officer, Class of 1962, and a part of the worldwide Global Smallpox Eradication Campaign of the late 1960s, early 1970s.
Small child stricken with smallpox
Find more information on this substance at: PubChem, PubMed