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.

After several weeks at a “moderate” risk level, the COVID-19 transmission risk has dropped to “low” in the four communities involved in the Contact Tracing Collaborative, which consists of Greenfield, Deerfield, Montague and Sunderland.

Wastewater levels increased slightly last week compared to the previous week, with 476,000 copies of virus per liter detected in the most recent sample, according to the Contact Tracing Collaborative. Cluster infections (of three or more people at one site) decreased from two to one. The positivity rate, meanwhile, held relatively steady at 4.35% compared to 4.2%. Average daily hospitalizations decreased from 2.29 to 1.43.

As a result, the municipalities are in the green zone, with a “low” risk of COVID-19 transmission. Masking is optional.

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.

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