A multi state MMR outbreak in the U.S. -- Iowa, Minnesota, Kansas, Illinois, Nebraska, Wisconsin, Missouri and Oklahoma -- in December, 2005...is the largest U.S. epidemic in nearly 20 years.

Health officials are attempting to determine why a significant number vaccinated became afflicted.

Encephalitic complications is a grave consequence with death and permanent neural damage -- the rate of attrition is based on decades old data and as vaccinated Americans are struck, new fungal factors may be in play.

However, college aged students in Iowa may not have been vaccinated. Whether this was due to a lapse in immunization or new citizens was not disclosed.

The strain in the early cases of the U.S. outbreak is identical to that in the United Kingdom, where the circulating virus has stricken 100,000 people.