The computer worm has burrowed into Reno and Washoe County government systems.
It hit late Monday afternoon and infected hundreds of computers within 20 minutes.
Technicians were racing to clean hundreds of terminals after the city-county network was all but shut down.
"I expect this virus to probably create problems for us over the next two to three days," said Rick Vandenberg, Reno communications and technology director.
To halt its spread, technicians required all city and county computers except in the public safety dispatch center to be turned off until the worm could be removed and a patch applied to prevent it from resurfacing.
The patch requires technicians to visit each of the more than 1,000 terminals at 57 locations throughout the city.
County techs hoped to have some 3,000 terminals back on line by late Wednesday.
During the outage, county departments resorted to conducting business manually. Court proceedings were not interrupted.
"They issued five marriage licenses by hand last night and did five more this morning," county spokeswoman Kathy Carter said on Tuesday.
Officials are not yet certain how the computer systems were infected.