The NFL Players Association announced 59 athletes have tested positive for COVID-19 as of Tuesday.
The results come as teams begin welcoming rookies to training camps, with full rosters expected to report by July 28.
On Monday, the NFL and NFLPA announced testing for the coronavirus would occur daily for the first two weeks of training camp as part of an agreement reached by the two sides. If the positivity rate falls below 5 percent after two weeks, testing will move to every other day.
Players must produce two negative tests that are separated by 72 hours before they can enter team facilities.
"Our union has been pushing for the strongest testing, tracing and treatment protocols to keep our players safe," the NFLPA said in a statement. "The testing protocols we agreed to are one critical factor that will help us return to work safely and gives us the best chance to play and finish the season."
An unnamed owner previously told NFL.com's Judy Battista they expect a notable number of positive tests as training camps open before confirmed cases begin to level off.
Testing is only one part of the health and safety plan that the league and union are negotiating.
The NFLPA is reviewing individual infectious disease emergency response plans from each franchise. Of the 32 plans received, the union has approved just eight. The remaining 24 are under consideration.
On Sunday, a number of prominent NFL stars participated in a social media campaign to force the league to act urgently in crafting health and safety guidelines this season. Patrick Mahomes, Drew Brees, J.J. Watt, Russell Wilson were among those who demanded a clear plan with training camp approaching.
While the testing issue has seemingly been solved, a number of questions remain, though ESPN's Adam Schefter reported Monday that more agreements are imminent.