On April 8, the National Guard arrived at Elkton Federal Prison in Columbiana County to assist the medical staff when a large number of prisoners became ill with the virus.[127] On April 18, the National Guard and Highway Patrol arrived at the state prison in Marion county to assist with "mission critical functions" after infections of correctional workers and prisoners.[128] By April 19, over 1800 prisoners at Marion Correctional Institution, approximately 3/4ths of the population, plus 100 staff had tested positive.[129] Overall the prison system had almost 2500 cases by April 19, representing almost a fifth of Ohio's cases.[129] On April 20 Acton said the prison testing results were indicating that as many as 70% of cases may be asymptomatic.[130]