It is generally a mystery how new diseases arise and how the pathogens that cause them first enter countries. However, clues may come from examination of specimens from similar outbreaks. This approach has recently been taken by scientists at the University of Veterinary Medicine, Vienna to trace the origin of the virus that caused a sudden decrease in the number of blackbirds in Vienna in 2001. The results are published in the current issue of the journal "Emerging Infectious Diseases."
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