Their first finding was that "cowpox" may actually comprise a number of distinct species. The researchers found a high degree of variation between samples, with the sequences clustering into five distinct "clades" or groups, each of which could be considered to represent a separate species. This is in contrast to prevailing wisdom, which considers cowpox to be a disease with a single causative agent. The second surprising finding was that the strains used in smallpox vaccines were most closely related to cowpox virus isolates from Russia, Finland and Austria rather than to samples from England. This suggests that commercial smallpox vaccines were not derived from Jenner's original strain but instead from somewhere in central or eastern Europe.
The last reported case of smallpox was in 1977 and in 1979 the World Health Organization declared that the disease had been eradicated. To date, smallpox is the only human viral disease to have been fully eradicated. Because smallpox is no longer a threat and because vaccination against it was occasionally associated with unpleasant side-effects, wide scale vaccination ceased in the early 1980s and fewer people are now immune to smallpox and related viruses, such as monkeypox and cowpox. As a consequence, these diseases are increasingly recorded in man. The incidence of monkeypox in the Democratic Republic of the Congo (the country with the most cases) has risen twenty-fold since the 1980si and 2003 saw a serious outbreak of the disease in the US.
As Jenner noted in the 18th century, the cowpox virus is also readily transmitted to man. D
|Contact: Beate Zoechmeister|
University of Veterinary Medicine -- Vienna