Analysis: A look at cumulative COVID-19 trends

Analysis: A look at cumulative COVID-19 trends
An illustration of the COVID-19 virus. (Image/Centers for Disease Control and Prevention)

By Denise Dunbar |

The seven-day COVID-19 average positivity rate on the Virginia Department of Health website is the best indicator of how a city is trending with cases, while the Virginia Hospital & Healthcare Association site tracks trends in current hospitalizations. This is the best indicator of current COVID-19 severity.

Fortunately, there is positive news on both fronts: Alexandria’s seven-day COVID-19b positivity rate fell from 6.2% on Aug. 24 to 4.5% on Sept. 1, while Virginia’s current hospitalization seven-day average dropped from 1,204 on Aug. 24 to 1,108 on Sept. 1.

How Alexandria stacks up against other localities cumulatively since the coronavirus swept into Virginia six months ago is more difficult to evaluate. The positivity rate is a useful tool for analyzing current COVID-19 levels, but it doesn’t account for case severity, and it’s also current, not cumulative.

In an effort to compare how localities have fared cumulatively, this article will examine COVID-19 case, hospitalization and death data relative to a locality’s population. It’s also important to take a look at localities’ hospitalization and death rates relative to their cumulative case totals, examining factors like location, density and racial and age demographics to help explain trends.

Prince William County and the City of Alexandria have the highest rates of cumulative COVID-19 cases per 100 residents in Northern Virginia, with 2.8 and 2, respectively. Paradoxically, these two localities also have the lowest death per case ratio in the region, with Prince William at 1.63 deaths per 100 cases and Alexandria at 1.84.

The numbers for Fairfax and Arlington counties are almost an inverse of Alexandria and Prince William. Fairfax and Arlington have significantly fewer cases per 100 residents, with 1.61 and 1.5 respectively, but Fairfax’s death rate per case is almost double that of Alexandria and Prince William, while Arlington’s is more than double.

A locality’s percentage of minority residents likely accounts for some of its COVID performance. Alexandria and Prince William have the highest percentage of Black and Latino residents relative to their overall population. Alexandria’s Black and Latino residents combine for 39% of the total population, while 47% of Prince William County’s residents are Black or Latino, according to U.S. Census Bureau data.

Many residents in these communities appear to have continued working at frontline jobs that have put them at greater risk of contracting COVID-19, which could help explain Alexandria and Prince William’s higher case per resident rate.

While vastly over-represented in cases, the combined Black and Latino residents of Alexandria and Prince William are more accurately reflected when it comes to COVID-19 deaths. In Alexandria, 25 out of 61 COVID-19 deaths designated by race and ethnicity, or about 41%, have been Black or Latino residents. That is slightly above but similar to their 39% representation in Alexandria’s overall population.

In Prince William the gap is slightly larger: 116 out of 218 COVID-19 deaths identified by race and ethnicity, about 53%, have been Black or Latino residents, while these groups comprise 47% of the population.

This again contrasts with Arlington County, where Black and Latino residents have been disproportionately hard-hit by severe cases of COVID. While they make up only 26% of residents, Blacks and Latinos account for 58 out of 141, or 41%, COVID-19 deaths identified by race and ethnicity.

Lower median age may also help explain why some localities have fewer severe COVID-19 cases than others. Fairfax County, Alexandria and Prince William County follow that basic model: Fairfax has the oldest median age in the region, 38 years, while Alexandria and Prince William are, respectively, 1.6 and 2.6 years younger on average. Fairfax County’s case per resident rate is lower than Alexandria and Prince William’s, but Fairfax residents have endured much higher rates of hospitalization and death per case.

Zip code COVID-19 and U.S. Census Bureau data has indicated that Latino residents in particular seem to be younger, which likely helps explain the lower rates of hospitalization and death per case in Prince William and Alexandria.

Arlington County’s experience with age as a predictor defies these trends. It has the lowest median age in Northern Virginia, at 34.4 years, yet by far the highest death rate per cumulative case in the region. Arlington’s rate of deaths per 100 residents is 50% higher than Alexandria’s, while Arlington’s death rate per COVID-19 case is more than double that of Alexandria: 3.9 people out of every 100 to contract COVID-19 have died in Arlington County, while Alexandria’s death rate is 1.8%.

Loudoun County is the outlier in Northern Virginia, with the lowest rate of cases per 100 residents, 1.47; lowest rate of deaths per 100 residents, .03; and lowest hospitalization rate per 100 cases, 6.42. Loudoun’s location further outside of D.C. than its regional counterparts and its significantly lower level of density – just 747 residents per square mile – could likely explain these numbers.

Location and density don’t explain the fact that Arlington has fared significantly worse than Alexandria with COVID-19 hospitalizations and deaths. Both localities lie inside the beltway, and they have the highest and second highest densities in Virginia. Alexandria is first with 10,399 residents per square mile, and Arlington has 8,918, according to

COVID-19 outbreaks may explain the discrepancy between Alexandria and Arlington’s death rates. While both localities have had 19 overall COVID outbreaks, as defined by the VDH, 14 outbreaks in Arlington have been in long-term care facilities, compared to 11 in Alexandria. In addition, Arlington’s overall outbreaks have included 565 cases, more than 200 higher than Alexandria’s 324.

A look at four other cities around the state – Danville, Norfolk, Richmond and Roanoke – reveals some similar age-related COVID-19 trends. Norfolk, at 30.4 years, and Richmond, at 33.5 years, have by far the lowest median ages of the four cities. Norfolk and Richmond also have the highest rate of cases relative to population and the lowest death rate per case of these cities.

Conversely, Danville has by far the oldest median population, at 41.1 years, and its COVID death rate per resident is twice that of the other three, .04 compared to .02. Its death rate per 100 COVID cases of 2.64 is also more than double that in the other three cities, though it’s still considerably lower than those of Arlington and Fairfax counties.

Racial demographics don’t seem to be the determining factor in these cities, as all four have similar combined Black and Latino populations of between 50 and 54% of their total residents. All but Danville had a lower death rate per case than the statewide average.

COVID-19 Outcome charts