As Massachusetts high schools begin a new, pandemic-altered sports season, data obtained by GBH News shows that the state Department of Public Health identified more than 130 clusters of COVID-19 linked to organized athletics between late July 2020 and late January 2021.

The largest event, in terms of confirmed cases, was logged by the state on Nov. 20, 2020, months before effective COVID-19 vaccines were available to the general public. That cluster featured 15 confirmed cases and affected individuals residing in Abington and Marlborough.

On Oct. 20, a sporting event was logged that involved 14 confirmed cases affecting residents of Ashland, Framingham and Newton.

Several events that involved 12 confirmed cases occurred during this period, with many affecting individuals residing in a large number of communities.

On Dec. 20, for example, DPH logged an event linked to a dozen confirmed cases — as well as 56 contacts, or people determined to be exposed — which affected residents of Reading, Essex, Middleton, Wakefield, Hamilton, Swampscott, Lynnfield, Haverhill, Wenham, Topsfield, North Andover, Beverly, Peabody, Saugus, Ipswich, Newburyport, Stoneham, Marblehead, Danvers and Georgetown. The investigation into that case remains open.

Many of the athletic clusters tracked by DPH were small, featuring between less than five confirmed cases.

According to DPH, 82 of the school-related clusters that occurred between late July and late January were linked to ice hockey, while 19 involved basketball. Eight were associated with soccer, three with football and two each with baseball, cheerleading, gymnastics, lacrosse and swimming. That breakdown suggests that ten athletic clusters tracked by DPH were not school-related.

On Oct. 22, Gov. Charlie Baker shut down indoor ice rinks for two weeks after at least 30 clusters involving ice hockey were identified. At the time, Baker and Health and Human Services Secretary Marylou Sudders said several teams were actively impeding the state’s contract-tracing efforts.

The information furnished by DPH leaves some key questions unanswered. For example, It doesn't say whether individual clusters were driven by sports-related activities like practice or game play, or by ancillary activities like socializing between players or spectators.

The ages of the persons affected is also unclear from the data provided, as is the impact on schools and workplaces as individuals were diagnosed and their family members, friends and acquaintances responded.

Still, the new data offers the fullest picture yet of how the decision to continue athletic activities during the pandemic — at a time when the public was repeatedly urged to limit contacts with anyone outside their household — may have impacted public health.

During the pandemic, the Massachusetts Executive Office of Energy and Environmental Affairs established statewide guidelines for youth and adult amateur sports, which have been adjusted as the broader COVID-19 context shifted.

In addition, the private, member-driven Massachusetts Interscholastic Athletic Association has altered seasonal sports schedules and issued rules modifications aimed at reducing the risk of coronavirus transmission. For example, high-school basketball during the pandemic featured no jump balls, fewer players rebounding free throws and a six-foot buffer zone for defenders guarding an inbounds pass.

The final sports season of the 2020-2021 academic year for most Massachusetts high schools begins Monday and runs through July 3. It includes track and field, baseball, golf, lacrosse, tennis, rugby, softball and boys' volleyball.

While many participants will benefit from the protection of vaccines not available in previous seasons, others will not be old enough to be vaccinated or will come from families that that choose not to take that step.