The death toll remained unchanged at 12 for the last week, and APHIS said no newly identified premises with suspected or confirmed cases had been identified during the reporting period, showing clearly that authorities had contained the outbreak.
Of the 88 confirmed cases, 58 of the cases were among horses that attended the National Cutting Horse Association Western National Championship event in Ogden, Utah, from April 29 to May 8, 2011.
In all, 33 of the 88 cases had neurological signs and were therefore diagnosed with EHM.
Other horses were infected after contact with the Ogden animals.
In all, 10 states have had cases as a result of the outbreak - Arizona, California, Colorado, Idaho, New Mexico, Nevada, Oklahoma, Oregon, Utah and Washington.
Of the 12 fatalities, 10 had attended at Ogden, while the other two caught the virus after being exposed to infected horses.
The latest APHIS report can be read here.