After adding over 36,000 new cases on May 13, the U.S. now has more than 32.4 million confirmed cases of COVID-19. There have been more than 570,000 COVID-19-related deaths — the highest death toll of any country.

New cases continue to rise at a steady rate. In the past week, there were an average of 13.6 daily new coronavirus cases per 100,000 Americans — essentially unchanged from the week prior, when there were an average of 15.3 daily new coronavirus cases per 100,000 people.

While COVID-19 has spread to nearly every part of the country, cities continue to be the sites of major outbreaks. Experts agree that the virus is more likely to spread in group settings where large numbers of people routinely have close contact with one another, such as colleges, nursing homes, bars, and restaurants. Metropolitan areas with a high degree of connectivity between neighborhoods and a large population may be particularly at-risk.

The Chicago-Naperville-Elgin, IL-IN-WI, metro area consists of Cook County, DuPage County, Lake County, and 11 other counties. In the past week, there were an average of 17.7 new coronavirus cases every day per 100,000 Chicago residents, in line with the national figure. The metro area’s average daily case growth in the most recent week is essentially unchanged from the week prior, when there was an average of 20.6 daily new cases per 100,000 Chicago residents.

The spread of coronavirus depends on a variety of factors and can vary even between neighboring counties. Within the Chicago-Naperville-Elgin metro area, COVID-19 is growing the fastest in Grundy County. There were an average of 23.5 new cases per day per 100,000 residents in Grundy County during the past week, the most of the 14 counties in Chicago with available data.

Case growth in the Chicago metro area varies at the county level. In Kenosha County, for example, there were an average of 10.8 new cases per day per 100,000 residents in the past week — the least of any county in Chicago and more than the case growth rate in Grundy County.

Just as Grundy County is driving the growth of COVID-19 in the Chicago area, it also has the highest incidence of cases overall. As of May 13, there were a total of 11,577.8 confirmed cases per 100,000 residents in Grundy County, the most of the 14 counties in the metro area. For comparison, the U.S. has so far reported 9,997.3 cases per 100,000 Americans nationwide.

In order to slow the spread of COVID-19, city and county governments have ordered the closure of thousands of consumer-facing businesses. These measures have led to widespread job loss and record unemployment. In Grundy County, unemployment peaked at 16.8% in April 2020. As of March 2021, the county’s unemployment rate was 6.6%.

To determine the county in every metropolitan area where COVID-19 is growing the fastest, 24/7 Wall St. compiled and reviewed data from state and local health departments. We ranked counties according to the average number of new daily COVID-19 cases per 100,000 residents in the seven days ending May 13. To estimate the incidence of COVID-19 at the metropolitan level, we aggregated data up from the county level using boundary definitions from the U.S. Census Bureau. Population data used to adjust case and death totals came from the U.S. Census Bureau’s 2019 American Community Survey and are five-year estimates. Unemployment data is from the Bureau of Labor Statistics and is not seasonally adjusted.

These are all the counties in Illinois where COVID-19 is slowing (and where it’s still getting worse).

Rank in MSA	County	Population	New daily cases per 100,000, week ending May 13	New daily cases per 100,000, week ending May 6	Cumulative cases per 100,000	Cumulative deaths per 100,000
1	Grundy County	50,666	23.5	27.6	11,577.8	148.0
2	Porter County	168,636	22.0	26.9	11,134.0	182.6
3	Jasper County	33,447	21.2	20.2	10,942.7	140.5
4	Will County	689,315	20.8	25.1	10,915.2	143.5
5	Kendall County	126,054	20.4	25.4	10,291.6	73.8
6	Kane County	531,376	19.0	24.1	10,951.2	144.9
7	Lake County	485,707	18.9	20.4	11,070.7	199.7
8	McHenry County	307,714	17.8	24.0	9,255.7	92.6
9	Cook County	5,198,275	17.6	19.9	10,458.4	193.9
10	DuPage County	929,060	16.3	20.0	9,715.8	137.5
11	DeKalb County	104,366	16.3	26.3	9,426.4	114.0
12	Newton County	13,992	14.9	13.9	7,704.4	243.0
13	Lake County	701,473	14.5	16.1	9,549.0	140.6
14	Kenosha County	168,524	10.8	13.8	10,893.4	192.3

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