The red squirrel's range spans northern Europe to Asia, but it is considered endangered in the United Kingdom. The main problem is that the Eastern gray squirrel, introduced from North America, has spread across most of the United Kingdom. Gray squirrels normally outcompete the reds, and they carry a deadly virus called squirrelpox, which quickly kills red squirrels. Yet the tide may be turning. The Isle of Anglesey is now free of grays, thanks to an eradication project that took 18 years.