SHELTON — The city’s total number of positive COVID-19 tests jumped 11, increasing to 643, over the past four days, according to Naugatuck Valley Health District data released Friday.

The increase comes as three “school community members” — one each at Shelton Intermediate School and Shelton High and another at Perry Hill School — tested positive for the virus. The health district is spearheading contact tracing, interim schools Superintendent Beth Smith said.

With eight staffers at Shelton High and another five at Shelton Intermediate being quarantined as a result of the positive tests, Smith said both schools will be on full distance learning from Oct. 13, to Oct. 22. The schools will reopen on a hybrid model on Oct. 23.

Ten of the positive cases in the city were reported in the past 24 hours, according to the data.

“Community transmission is still occurring,” NVHD Director Jessica Stelmaszek said earlier in the week, “and people should not let their guards down.”

Shelton’s 643 positive cases remain significantly more than other Valley communities. Naugatuck stands at 472 positive tests, followed by Ansonia with 305, Seymour at 240, Derby with 192 and Beacon Falls at 60.

No new deaths were reported, and Shelton has remained at 137 deaths from COVID-19-related complications for some time.

NVHD data shows that 251 of the 643 confirmed cases are individuals who resided in a nursing home, assisted living facility, group home or other similar setting at the time of the testing.

brian.gioiele@hearstmediact.com