Helping hands logo

UPDATED March 27: YourArlington continues to report weekly a running tally here of statistics of Covid-19 incidence regionally, listed in reverse chronological order. (Information from a government website quoted at the end of this column suggests that numbers are more meaningful when considered over several weeks.)

The number for Middlesex County, where the Town of Arlington is located, was down at the most recent reading, to 366, down from 588 a week prior. Middlesex County is currently just below the nationwide average, which currently stands at 379.

The county is the only one last week to have its number drop notably. Two other counties -- Berkshire and Hampshire -- are essentially level with their tally of the previous week. The other nine are up since March 15: Barnstable, Bristol, Essex, Franklin, Hampden, Nantucket, Plymouth, Suffolk and Worcester.


The numbers cited here represent Covid-19 virus concentration per mililiter of wastewater; however, this is not the same as the number of Covid-19 cases, which is almost impossible to know currently. 

These numbers typically are posted each Thursday evening, based on the previous day's results, by Biobot Analytics, a relatively new, female-led, Cambridge, Mass.-based firm that samples and analyzes wastewater nationwide.

Throughout the United States, Biobot reports numbers county-by-county within each state, displaying them graphically and comparing them to the U.S. average for each week. 

The list of weekly reported numbers for Middlesex County, starting with Nov. 9, 2022, is given further down in this article. The longest stretch of relatively high numbers recently in Middlesex County ran from Nov. 30, 2022, through Jan. 18, 2023. The county's weekly number has varied since then but has been in only triple digits for the past two months.

As of August 2022, the Town of Arlington no longer routinely tested for Covid-19 nor compiled statistics about local infection rates, making Biobot’s information likely the best currently known, most understandable and publicly available. Many mainstream experts consider analysis of wastewater to be a particularly good metric because samples are anonymous, involuntary and universal.

Many mainstream experts contend that other Covid-19 statistics, being primarily based on public testing sites, physician notes and hospital records, may be significantly undercounting the true total number of infections, especially as asymptomatic individuals rarely are accounted for. This is because people with non-existent, mild or moderate symptoms of possible Covid-19 sometimes cannot or will not seek medical attention, cannot or will not use nasal-swab-based home tests, or cannot or will not report their positive test results to authorities.

Biobot’s home page demonstrates the national picture. This page if one scrolls down a bit and looks to the left side can be used to show the graphs and numbers for all 12 counties in Massachusetts; these graphs also compare each county to the national picture for the same timeframes. One may select to see the charts/numbers for the past six weeks, the past six months or overall for the past three years.

Recent numbers to date for Middlesex County, Mass., per Biobot Analytics are as follows:

March 22, 2023: 366

March 15, 2023: 588

March 8, 2023: 438

March 1, 2023: 435

Feb. 22, 2023: 542

Feb. 15, 2023: 678

Feb. 8, 2023: 881

Feb. 1, 2023: 774

Jan. 25, 2023: 890

Jan. 18, 2023: 1,118

Jan. 11, 2023: 1,461

Jan. 4, 2023: 1,879

Dec. 28, 2022: 2,452

Dec. 21, 2022: 2,145

Dec. 14, 2022: 2,411

Dec. 7, 2022: 1,417

Nov. 30, 2022: 1,347

Nov. 23, 2022: 867

Nov. 16, 2022: 771

Nov. 9, 2022: 695

A page from the website of the Massachusetts Department of Public Health explains the significance of wastewater analysis as follows: "The amount of virus that a person has in their stool and the length of time that they have virus in their stool varies. Because of this, the amount of virus measured in wastewater does not tell us the total number of cases in an area and does not tell us the amount of increase or decrease in cases in communities. However, if the amount of virus in wastewater increases or decreases over several time points, that information shows that cases are either increasing or decreasing in the community. Importantly, wastewater data can provide an early warning about increasing cases, since virus will show up in wastewater several days, maybe even a week, before positive test numbers start to increase."


Jan. 6, 2023: Majority at town public schools wear masks, complying with ‘strong recommendation’


This column by YourArlington Assistant Editor Judith Pfeffer was first published Jan. 7, 2022. It was updated Jan. 9 to change the headline for greater accuracy and updated Jan. 10 to state what Biobot Analytics measures; to note that the weekly list is presented toward the end of the article; and to provide additional context. It was updated Jan. 12 to post the latest available weekly number and to include at the end a paragraph from a state website describing the scientific importance of wastewater analysis. It has since been updated Jan. 19, Jan. 26, Feb. 3, Feb. 10, Feb. 17, Feb. 25, March 1, March 10, March 17 and March 27 with the latest data reported publicly by Biobot Analytics of Cambridge, Mass.