Thirty-eight counties in Ohio are now listed in the red under the state's coronavirus alert system. That's 74% of the state's population currently living in a red county.

This is an increase from 29 counties last week.

Five counties - Crawford, Geauga, Lake, Ottawa and Tuscawaras - are red for the first time since the system was introduced.

Gov. Mike DeWine announced three of those counties - Clark, Cuyahoga and Hamilton - are on the watch list for purple (Level 4). 

According to the state's advisory system, a purple county is dealing with "severe" exposure and spread. Residents would be advised to only leave home for supplies and services. To date, no county has hit that level.

With only four counties at yellow (Level 2), DeWine said this is the highest number of red counties and the lowest of yellow.

DeWine said 92.8% of Ohioans are currently living in a county with "very high exposure" and spread of COVID-19  saying, "We cannot let our guard down."

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HOW IT WORKS: Ohio Public Health Advisory System 

The public health advisory system has seven indicators to help determine a county's level:

1. New cases per capita: Triggered when a county has an average of 50 cases per 100,000 people over a two-week period
2. Sustained increase in new cases: Triggered by a five-day period of sustained growth
3. Proportion of cases not congregate cases: Triggered when at least half of new cases originate from non-congregate settings during at least one of the past three weeks
4. Sustained increase in ER visits: Triggered by an increase in COVID-19-related emergency room visits over a five-day period
5. Sustained increase in outpatient visits: Triggered by an increase in COVID-19-related visits to outpatient settings (such as telehealth appointments) over a five-day period
6. Sustained increase in new COVID-19 hospital admissions: Triggered by a five-day period of sustained growth in new admissions
7. ICU bed occupancy: Triggered when at least 80% of a county's ICU beds are occupied over at least three of the last seven days

For however many indicators a county meets, they will be placed into one of four color-coded levels to display the possible risks involved:

• Level 1 (yellow, 0-1 indicators): Displays active community spread; all current health orders should be followed
• Level 2 (orange, 2-3 indicators): Displays increased exposure and spread; besides following all current orders, residents should also exercise a "high degree of caution"
• Level 3 (red, 4-5 indicators): Displays "very high" exposure and spread; residents should limit activities as much as possible
• Level 4 (purple, 6-7, indicators): "Severe" exposure and spread; only leave home for supplies and services