Smallpox was not notably infectious in the prodromal period and viral shedding was usually delayed until the appearance of the rash, which was often accompanied by lesions in the mouth and pharynx. The virus can be transmitted throughout the course of the illness, but this happened most frequently during the first week of the rash when most of the skin lesions were intact. Infectivity waned in 7 to 10 days when scabs formed over the lesions, but the infected person was contagious until the last smallpox scab fell off.Smallpox was highly contagious, but generally spread more slowly and less widely than some other viral diseases, perhaps because transmission required close contact and occurred after the onset of the rash. The overall rate of infection was also affected by the short duration of the infectious stage. In temperate areas, the number of smallpox infections was highest during the winter and spring. In tropical areas, seasonal variation was less evident and the disease was present throughout the year. Age distribution of smallpox infections depended on acquired immunity. Vaccination immunity declined over time and was probably lost within thirty years. Smallpox was not known to be transmitted by insects or animals and there was no asymptomatic carrier state. Mechanism
Once inhaled, the variola virus invaded the mucus membranes of the mouth, throat, and respiratory tract. From there, it migrated to regional lymph nodes and began to multiply.
Shrines were created where many Indian natives, both healthy and not, went to worship and attempt to protect themselves from this disease. Some Indian women, in an attempt to ward off Shitala, placed plates of cooling foods and pots of water on the roofs of their homes.In cultures that did not recognize a smallpox deity, there was often nonetheless a belief in smallpox demons, who were accordingly blamed for the disease. Such beliefs were prominent in Japan, Europe, Africa, and other parts of the world. Nearly all cultures who believed in the demon also believed that it was afraid of the color red. This led to the invention of the so-called red treatment, where patients and their rooms would be decorated in red. The practice spread to Europe in the 12th century and was practiced by (among others) Charles V of France and Elizabeth I of England. Afforded scientific credibility through the studies by Niels Ryberg Finsen showing that red light reduced scarring, this belief persisted even until the 1930s. See also
List of epidemics
Population history of indigenous peoples of the Americas#Depopulation from disease

References
Further reading
External links

Smallpox Biosafety: A Website About Destruction of Smallpox Virus Stocks
Detailed CIDRAP Smallpox overview
Agent Fact Sheet: Smallpox, Center for Biosecurity
Smallpox Images and Diagnosis Synopsis Archived 29 July 2008 at the Wayback Machine
Virus Pathogen Database and Analysis Resource (ViPR): Poxviridae
Episode 1 (of 4): Vaccines of the BBC Four and PBS show: Extra Life: A Short History of Living Longer (2021)