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This illustration, created at the Centers for Disease Control and Prevention, reveals the structure of the novel coronavirus. The illness caused by this virus has been named COVID-19.

The rate of new coronavirus cases declined slightly in Pennsylvania last week, but some counties saw sharp increases.

An outbreak at the U.S. Penitentiary at Lewisburg helped to pushed tiny Union County, in the northcentral part of the state, to the top of the state list. Its 65 new cases gave it a one-week rate of 145 new cases per 100,000 population.

According to the U.S. Bureau of Prisons, Lewisburg has 18 active inmate cases of COVID-19 and one staff case, and 34 inmates and one staff member have recovered.

Union County’s rate of new cases for the seven-day period of Aug. 4 through 10 was nearly twice the rate of second-place Mercer County, on the Ohio border, at 79 cases per 100,000.

Lancaster ranked 10th, at 54 cases per 100,000, down from 65 the week before. Several other central Pennsylvania counties were close behind.

The statewide rate was 41 new cases per 100,000, down from 46 in the seven-day period of July 28 through Aug. 3.

Here are the 10 counties with the highest per-capita rates of new cases from Aug. 4 through 10, and how their rates compare with the previous week:

1) Union: 145 per 100,000 (Up from 109 the week before)

2) Mercer: 79 (Up from 51)

3) Northumberland: 75 (Up from 29)

4) Delaware: 73 (Down from 86)

5) Fayette: 67 (Down from 77)

6) Indiana: 56 (Down from 62)

7) Beaver: 54 (Down from 67)

8) Franklin: 54 (No change)

9) Lycoming: 54 (Up from 35)

10) Lancaster: 54 (Down from 65)

Three counties that border Lancaster were only a little below it on the list. York ranked 11th, with just under 54 new cases per 100,000 population (up from 37 the week before). Dauphin was 12th, with 53 cases per 100,000 (up from 44), and Berks was 20th, at 45, up from 41 the week before.