Because variola minor was a less debilitating disease than smallpox, patients were more frequently ambulant and thus able to infect others more rapidly. As such, Variola minor swept through the United States, Great Britain, and South Africa in the early 20th century, becoming the dominant form of the disease in those areas and thus rapidly decreasing mortality rates. Along with Variola major, the minor form has now been totally eradicated from the globe. The last case of indigenous Variola minor was reported in a Somali cook, Ali Maow Maalin, in October 1977, and smallpox was officially declared eradicated worldwide in May 1980. Variola minor was also called white pox, kaffir pox, Cuban itch, West Indian pox, milk pox, and pseudovariola. Genome composition
The genome of Variola major is about 186,000 base pairs in length. It is made from linear double stranded DNA and contains the coding sequence for about 200 genes. The genes are usually not overlapping and typically occur in blocks that point towards the closer terminal region of the genome. The coding sequence of the central region of the genome is highly consistent across orthopoxviruses, and the arrangement of genes is consistent across chordopoxvirusesThe center of the variola genome contains the majority of the essential viral genes, including the genes for structural proteins, DNA replication, transcription, and mRNA synthesis. The ends of the genome vary more across strains and species of orthopoxviruses. These regions contain proteins that modulate the hosts immune systems, and are primarily responsible for the variability in virulence across the orthopoxvirus family.
Smallpox was an infectious disease caused by one of two virus variants, Variola major and Variola minor. The agent of variola virus (VARV) belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980, making it the only human disease to be eradicated.The initial symptoms of the disease included fever and vomiting. This was followed by formation of ulcers in the mouth and a skin rash. Over a number of days, the skin rash turned into the characteristic fluid-filled blisters with a dent in the center. The bumps then scabbed over and fell off, leaving scars. The disease was spread between people or via contaminated objects. Prevention was achieved mainly through the smallpox vaccine. Once the disease had developed, certain antiviral medication may have helped. The risk of death was about 30%, with higher rates among babies. Often, those who survived had extensive scarring of their skin, and some were left blind.The earliest evidence of the disease dates to around 1500 BCE in Egyptian mummies. The disease historically occurred in outbreaks. In 18th-century Europe, it is estimated that 400,000 people died from the disease per year, and that one-third of all cases of blindness were due to smallpox. Smallpox is estimated to have killed up to 300 million people in the 20th century and around 500 million people in the last 100 years of its existence. Earlier deaths included six European monarchs.