The Nevada Department of Corrections says it's planning to conduct widespread testing of inmates and staff after four inmates so far have tested positive for coronavirus.

The announcement this week comes after an inmate from High Desert State Prison tested positive for coronavirus after getting medical treatment at a community hospital. When others in his intake unit were tested, three more were found to be positive; all had recently arrived from the Clark County Detention Center.

On Tuesday, prison officials plan to test staff and offenders in other units at High Desert State Prison — the largest institution in the system with a capacity of nearly 4,200 and one that is located north of Las Vegas in Indian Springs.

The testing plan, which has been developed in coordination with the Nevada Department of Health and Human Services and the Nevada State Public Health Laboratory, "will help prevent asymptomatic transmission of the virus," prison officials said. 

"Our goal is to mitigate and prevent the spread of COVID-19 through rigorous testing and the implementation of deliberate and proactive protocols," said prisons director Charles Daniels.

On Wednesday, the prison agency will distribute 5,000 tests to medical staff and launch a campaign for widespread testing in the Nevada institutions, which have more than 12,000 inmates combined. 

Prison officials said offenders who test positive are isolated in negative airflow rooms in an infirmary, and staff who test positive are released from duty to quarantine. They must have approval from the agency's medical director to return to work.

A state dashboard indicates that 20 staff members have tested positive so far. That's in addition to the four inmates.