Essex County COVID-19 Cases are Above State Average

(Updated to May 26, 2020)

Haverhill parents, teachers, school administrators and city leaders all need to make plans about education from home and reopening of schools closed due to coronavirus (COVID-19). Some have suggested that decisions to reopen businesses and schools might eventually be made county by county if patterns of coronavirus cases differ greatly among counties. This Benchmark Blog post looks at data available to date on coronavirus cases by county for the largest eastern Massachusetts counties.

This post considers cumulative and daily data on number of confirmed COVID-19 cases for the period for March 20 through May 26, 2020.  Case counts come from Massachusetts Department of Public Health (DPH). County population figures come from the UMass Donahue Institute. I computed cases per 1000 of county population (2018) for the largest Massachusetts counties and statewide. Keep in mind that counts reflect not only the incidence of the disease but also the amount of testing that is done. For May 26 the state DPH reported  only 4,920 tests. Cumulatively 17.1 percent of all 545,481 tests were positive.

Chart 1 shows Essex and the other non-Boston areas are on lower paths than Suffolk County. Essex County confirmed case counts per capita are now consistently well above the statewide average after tracking very near the state average up to April 2nd.  Essex County cumulative cases per capita are now 27.4 percent above the state average, and 35.5 percent above neighboring Middlesex County.

Chart 1

Chart 2 shows results for new cases reported daily. The greater day-to-day variation reflects the smaller numbers and possible day-of-the-week differences (fewer new cases tend to be reported on weekends) for testing and/or reporting. Suffolk County is tracking higher than other counties. As noted below, cases counts from April 13 to April 22 were under-reported to DPH by one laboratory company. The delayed cases were included in counts April 23 and 24, producing the spike in counts for those days.

Chart 2

Chart 3 presents these data for new cases as a seven-day moving average. This smooths out the day-to-day variation and avoids any day-of-the-week reporting effects. Part of the flattening of the curves April 13 to 22 is due to under-reporting in that period (see note below). The corrections on April 23 and 24th inflated case counts for those days and also inflates the 7-day moving average through April 30. So the apparent decline on April 30 and May 1 is largely due to reporting (the correction moving out of the moving average).

Monitoring updates to this chart may help identify when the COVID spread begins to slow in Massachusetts counties. A slowing of the spread of the virus would be indicated by a downturn in the 7-day moving average of new cases (not counting the drop due to reporting adjustment at the end of April).

Chart 3

Recently, in the first half of May, average new cases per capita declined particularly in Suffolk and Essex Counties, which had the highest rates in April. New cases are also trending downward statewide. Worcester County has seen the least decline and its new cases per capita are now tracking above the state average. With an apparent gradual decline in May, the rate of new COVID-19 cases in the larger Eastern Massachusetts counties are now closer together in the range of 10 to 20 daily new cases per 100,000 population.

There were 5,768 new confirmed COVID-19 cases in Massachusetts in the past seven days to May 26. This is down from 8,593 cases in the seven days preceding that period. These case counts, which reflect intensity of testing as well as prevalence of COVID-19, show the continued need for diligent social distancing and caution about reopening nonessential  businesses.  They do not yet point to an early end to COVID-19 threats in Essex and other eastern Massachusetts counties.

Note: The Massachusetts Department of Public Health (DPH) on April 24th noted a reporting error that reduced case counts for data from April 13 to April 23 due to a backlog in reporting cases from Quest Diagnostics. DPH provided revised case counts for that period for Massachusetts, but not for individual counties. The results reported here thus reflect under-reporting of COVID case counts for April 13 to 22 and increased case counts for April 24 to account for the previous under-counts