Why has the disease spread so rapidly among House Finches?
The House Finch population is large, and the birds tend to move together in highly mobile foraging flocks. Therefore, diseased individuals are constantly entering new areas, increasing the chance of infecting other birds in that area. Also, some infected birds do not die from the disease, which increases the probability of its transmission to other individuals. Lastly, current evidence suggests that infected birds do not acquire immunity to future infections.
