Naturally occurring cases of<unk>  were not common, but it was discovered that the vaccine could be “carried” in humans and reproduced and disseminated human-to-human. Jenner's original vaccination used lymph from the<unk>  pustule on a milkmaid, and subsequent “arm-to-arm” vaccinations applied the same principle. As this transfer of human fluids came with its own set of complications, a safer manner of producing the vaccine was first introduced in Italy. The new method used cows to manufacture the vaccine using a process called “retrovaccination", in which a heifer was inoculated with humanized<unk>  virus, and it was passed from calf to calf to produce massive quantities efficiently and safely. This then led to the next incarnation, “true animal vaccine”, which used the same process but began with naturally-occurring<unk>  virus, and not the humanized form. This method of production proved to be lucrative and was taken advantage of by many entrepreneurs needing only calves and seed lymph from an infected cow to manufacture crude versions of the vaccine. W. F. Elgin of the National Vaccine Establishment presented his slightly refined technique to the Conference of State and Provincial Boards of Health of North America. A tuberculosis-free calf, stomach shaved, would be bound to an operating table, where incisions would be made on its lower body. Glycerinated lymph from a previously inoculated calf was spread along the cuts. After a few days, the cuts would have scabbed or crusted over. The crust was softened with sterilized water and mixed with glycerin, which disinfected it, then stored hermetically-sealed in capillary tubes for later use. At some point, the virus in use was no longer<unk> , but vaccinia. Scientists have not determined exactly when the change or mutation occurred, but the effects of vaccinia and<unk>  virus as vaccine are nearly the same. The virus is found in Europe, and mainly in the UK. Human cases today are very rare and most often contracted from domestic cats. The virus is not commonly found in cattle; the reservoir hosts for the virus are woodland rodents, particularly voles. From these rodents, domestic cats contract and transmit the virus to humans. Symptoms in cats include lesions on the face, neck, forelimbs, and paws, and less commonly upper respiratory tract infections. Symptoms of infection with<unk>  virus in humans are localized, pustular lesions generally found on the hands and limited to the site of introduction. The incubation period is 9 to 10 days. The virus is prevalent in late summer and autumn.
Cowpox
Sealpox
Smallpox
Chickenpox
Farmyard pox
Mumps
Rickettsialpox
Progressive vaccinia