COVID-19 numbers: what they mean, why they matter

With San Diego County moving to the Purple Tier, and new restrictions effective November 14, 2020, you’re likely closely monitoring the local COVID-19 numbers. These numbers are the metrics used by state and local authorities when determining which businesses and activities can open and which restrictions should be enforced.

Here’s what the numbers really mean and why they’re so important.

Understanding state guidelines

In California, state authorities use a four-tier, color-coded system — ranging from minimal spread of the disease to widespread — to determine whether a community is in the position to safely open businesses and other activities. California counties must stay in a tier for at least three weeks before being moved to a less restrictive tier, and will be moved to a more restrictive tier if metrics worsen for two consecutive weeks.

The state focuses on the following numbers to make a determination:

New cases: This number represents the daily number of confirmed COVID-19 cases per 100,000 people. If more than an average of 7 out of 100,000 people test positive each day of a seven-day period, the state would consider this “widespread.” On the other end of the spectrum, an average of less than one new daily case per 100,000 puts the county in the “minimal” tier, allowing most indoor business operations to be open with modifications.

Positive tests: This number is determined by looking at the number of COVID-19 tests with a positive result out of the total number of tests performed over a seven-day period. For example, if 100 tests are performed and 6 of those tests are confirmed positive, the percentage is 6%. California classifies a county’s risk level as minimal if less than 2% of tests are positive, and widespread if more than 8% are positive.

Understanding county guidelines

Along with new cases, also known as “case rate,” and positive tests, or “testing positivity,” the County of San Diego looks at several other numbers to determine whether the local health officer order should be modified, thus increasing or reducing restrictions. Using a “trigger” system, the county looks at additional metrics related to epidemiology, health care and public health that indicate the level of local COVID-19 activity, including the following:

Additional numbers to know

Along with the numbers the state and county use to determine the level of COVID-19 spread and how businesses and other activities may be affected, experts and the general public also look at the total numbers of COVID-19 cases, probable cases, deaths to date and where the cases are located. These numbers help us:

• Monitor the spread of the disease
• Understand illness severity
• Recognize risk factors for severe illness or death
• Track transmission of the disease
• Forecast virus spread
• Determine COVID-19’s overall impact on communities and the health care system

“It is important to mention that although the vast majority of the people who died of COVID-19 had preexisting conditions such as diabetes, high blood pressure and obesity, the exacerbating factor and the primary cause of death is the COVID-19 infection,” says Dr. Hai Shao, an infectious disease doctor affiliated with Sharp Chula Vista Medical Center. “Meanwhile, those comorbidities could greatly increase the risk of severe infection and death by COVID-19 infection, making certain population of the society more vulnerable to progress to severe infection and death once infected.”

According to the U.S. Department of Health and Human Services, up to 50% — 1 in every 2 people — of Americans 64 or younger have some type of preexisting condition, putting them in the high-risk category. “The best way to protect them from severe infection and death is to practice preventive measures, such as social distancing, wearing face coverings and frequent hand washing, to slow the transmission of COVID-19 in the society,” Dr. Shao says.

This article was adapted from Sharp Health News.

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