Editor’s note: The Greenfield Recorder has been providing regular updates on the risk level of COVID-19 transmission as wastewater testing results are received.

With copies of virus in the wastewater trending upward, the COVID-19 transmission risk has increased to “moderate” in the four communities involved in the Contact Tracing Collaborative, which consists of Greenfield, Deerfield, Montague and Sunderland.

As of Friday, there were 2.5 million copies of virus per liter of sewage, compared to a concentration of 1.6 million copies the week prior. Although average daily hospitalizations have increased from 1.1 to three, cluster infections (of three or more people at one site) have decreased from two to one and the positivity rate dropped from 4.76% to 3.15%, according to Greenfield Health Director Jennifer Hoffman.

As a result, the municipalities are in the yellow zone after two weeks in the green zone, with a “moderate” risk of COVID-19 transmission. Masking is encouraged.

Hoffman said public health officials continue to ask people to “stock up on test supplies” before the end of the national public health emergency in May. She also advised students to get tested before returning to school after February vacation this week.

In combination with wastewater testing — people with an active COVID-19 infection excrete the virus in their stool and samples from wastewater treatment plants can be analyzed to estimate community virus levels — the four municipalities factor in hospitalization numbers, positivity rates and case numbers to determine risk levels. Meanwhile, health officials continue to talk with nursing homes, businesses and schools to track cluster infections. Members of the collaborative added school absenteeism as an additional measure to compensate for the loss of PCR testing locally.

The following three zones, defined by the Contact Tracing Collaborative, are used to gauge risk levels of COVID-19 transmission in the four communities. For the risk level in the area to change, at least two measures need to apply.

Red zone: High COVID-19 risk

Masking recommended.

■Cluster infections (of three or more people at one site): five or more.

■Percent positive tests out of total tests performed: greater than 10%.

■Hospitalizations: five or more.

■Increase in case trend.

■Increase in wastewater trend.

Yellow zone: Moderate COVID-19 risk

Masking encouraged.

■One to four cluster infections.

■Stable positive testing.

■Fewer than five hospitalizations.

■Stable case incidence.

■Stable wastewater.

Green zone: Low to minimal COVID-19 risk

Masking optional.

■No cluster infections.

■Decrease in positive tests.

■Decrease in hospitalizations.

■Decrease in case incidence.

■Decreased virus copies in wastewater.

Reporter Mary Byrne can be reached at mbyrne@recorder.com or 413-930-4429. Twitter: @MaryEByrne.

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