In the seven weeks since the NBA season was suspended due to the coronavirus, the league has avoided speculation about how and when it may return. But as May 1 arrives with the league no closer to resuming, the idea of a quarantined zone where games could be played persists.

ESPN spoke to a range of stakeholders studying the "bubble" concept -- NBA coaches, referees and executives, infectious disease specialists, basketball operations specialists, TV producers and directors, as well as hotel and food workers -- and compared their needs and concerns with the league's thinking.

There are considerable logistical challenges to any attempt to finish the 2019-20 season. And though the situation around COVID-19 is constantly evolving, hope perseveres to eventually declare a 2020 champion. This is how an NBA bubble could work.

MORE: Latest updates amid coronavirus suspension

Testing is a must

When it comes to restarting play, NBA commissioner Adam Silver has said he'll follow the guidance of the Center for Disease Control and independent health advisers. And the one thing these health experts agree on is that testing is the key to everything.

There needs to be a fast, simple and reliable test. There also must be enough available public testing to avoid backlash toward the NBA for acquiring and using kits. The league expects it will need approximately 15,000 tests, sources told ESPN's Adrian Wojnarowski. Teams were sent a memo Thursday night advising not to arrange coronavirus tests for asymptomatic players and staff.

The NBA is working with academic centers, labs and medical test developers to contribute to advances in testing for sports and the public, but nationwide testing capacity is still falling short of where health advisers the league consults say it needs to be. Until that is resolved, it is unlikely the NBA would use such resources, league sources said.

"I do think it would be disturbing to many if there was massive testing that was available to a sports league at a time when people who are in high-risk situations were still having a difficult time getting access to testing," said Dr. Vivek Murthy, the former surgeon general who has advised the NBA on the coronavirus.

Medical experts differ on how often testing would have to be performed to maintain bubble integrity. Dr. Anthony Fauci, a key member of the White House's coronavirus task force, has suggested sports could resume with weekly testing of athletes, as long as they are closely watched.

There could be daily monitoring of symptoms, but that has limited effectiveness because asymptomatic carriers can be contagious before showing symptoms, several infectious disease specialists told ESPN.

"[Testing every day] would be my gold standard," said Carl Bergstrom, a professor of biology at the University of Washington, who has been closely following MLB and NBA plans and has discussed the logistics with stakeholders. "Figure out how to test everyone every day, and from there back out."

Still, this would leave unanswered questions. For example, the CDC says adults over 65 years old are at higher risk of severe illness or death from COVID-19. Would the NBA allow coaches such as Gregg Popovich (71) and Mike D'Antoni (68) to work?

False negatives and false positives also present issues. A return to play would need to be met by rigorous testing to account for both possibilities and to ensure the health and well-being of those inside the bubble.

The wide-ranging responses to risk tolerance from epidemiological experts highlight the complexities for the league in being able to provide guidance on a return-to-play plan or even the ability to outline a timeline.

How long would this experiment take?

When play abruptly stopped on March 11, there were 259 regular-season games remaining on the schedule. If the NBA were to complete those games and four rounds of playoffs, occupants could be in some form of a bubble for roughly three months.

Epidemiologists and infectious disease experts described the need "to create layers of protection" when returning to play. This would mean cutting the number of people to a minimum to reduce the possibility of infection and spread of the virus backed up with other measures like daily temperature checks. As a result, these experts recommend isolating participants from friends and family during this time.

This was ultimately an untenable concession. As the league evaluates options, sources said it has rejected the concept of quarantining players without family members. The hope is that advancements in testing could prevent such isolation measures.

"There are so many layers that would have to come into play for [a bubble] to even happen," Chris Paul, president of the National Basketball Players Association, said last week. "We would have to know exactly what that would look like. There's a lot of hypotheticals out there."

One of them is determining how long it would take for the league's players to get back into game shape. ESPN's Adrian Wojnarowski reported Monday the league plans to reopen some of its facilities May 8, but a return to full NBA practices remains far away.

In a scenario where the NBA played eight games per day -- using two courts to host concurrent games akin to summer league -- the regular season could be completed in 33 days with almost no back-to-backs. A full four-round postseason, with minimal days off, would take a maximum of 55 days to complete.

An alternative framework could shorten this timeline and reduce the number of people needed to finish the season by skipping directly to the playoffs using the current standings. Bringing in 16 teams rather than 30 would cut the number of people in the bubble roughly in half and potentially cut time away from home by more than a month.

The lower number of people also would keep contact between different teams to a minimum -- something medical officials advise would be prudent, as it would further reduce the chance of proliferation in the event of an infection.

Where could a bubble be established?

Several potential host locations have been in contact with the NBA to discuss the concept, and the league is already working on some modeling.

While Las Vegas has been a popular idea, with MGM Grand one of the suitors to host the NBA, sources told ESPN's Adrian Wojnarowski, Walt Disney World Resort in Orlando, Florida, has recently gained momentum. Regardless of the location, conversation around the league has circled around the G League Showcase as a single-site template.

For the past two years, the Showcase has been held at MGM's Mandalay Bay and has accommodated 28 teams. Under that setup, five courts are placed in a convention center -- two for games and three for practices -- with all of the teams staying at connected hotels under the same roof.

But experts recommend clustering teams into smaller groups as an extra safeguard against the spread of infection. Teams might need to stay and play in separate locations. One potential complication to multiple sites would be transportation. Movement via buses or other vehicles would increase the number of people needed in the bubble. This only becomes more difficult to navigate as regional pods are discussed, as the NHL is considering.

Also, holding an event of this size anywhere will require cooperation from local -- and possibly state -- governments as it could create more demand on local resources and open the door for the league's return-to-play operation to be subsidized in what would likely be both an expensive and high-profile endeavor.

Who is inside a bubble?

To reduce the probability of the virus being introduced and spread within the bubble, infectious disease experts said the NBA would have to operate with as few people as possible inside it. According to team and league personnel, referees, television producers and hotel general managers, that would amount to about 1,500 people being deemed as "essential" to restart the regular season.

Some of the work to determine essential personnel started weeks ago, as organizations braced for the likelihood of holding games without fans. In a memo to teams on March 7, the NBA said to "minimize the number of staff traveling with the team to essential individuals only."

This scenario would go even further. Consultation with head coaches and executives led to the reduction to 28 people per team: 15 active roster spots (excluding two-way players), the head coach, three assistant coaches, three trainers/physical therapists, a strength coach, an equipment manager, a team logistics coordinator, a front-office representative, a public-relations official and a security official. The typical team travel size ranges from 40 to 50 people, growing to 75 or more in the postseason.

Aside from team needs, game operations staff would need access.

There would need to be a set of people operating the clocks, scoreboard, compiling real-time statistics and communicating with the officials and both teams. There are two reasons for them to be physically present: accuracy and real-time betting purposes. They can't risk a delay by watching a feed prone to technological hiccups.

A public-address announcer also was deemed necessary, as he or she communicates what is happening on the court to both teams. They are used in the G League Showcase where fans are not in attendance.

Those combined duties require seven people for each game. Playing four games per day on two courts would mean needing around 42 people -- seven to work each set of two games during the days, seven work each set of two games at night, and two reserve sets to allow for a two-days-on, one-day-off rotation. There also would need to be ball boys -- likely two for each team per game -- to handle court and bench area maintenance.

To play out the remainder of the regular season and playoffs, a top referee official told ESPN the league would need about 36-38 referees. That accounts for three referees for the average of eight games played during the regular season, as well as having extra crews for rest and in case of injury. Using several sites would increase this number.

Multiple television producers believe games could be televised with as few as five manned cameras. And between shifts of camera operators and other personnel, roughly 20-25 people would be needed to broadcast the games. There would need to be television production trucks onsite to produce the broadcasts, but it is possible they could be housed outside of the building the games are in -- and thus kept separate from those playing and coaching in them.

Every NBA game also has emergency medical personnel on hand and an ambulance ready. How these people would fit into the bubble is uncertain, as it potentially represents a strain on health care resources.

Essential support staff

NBA teams typically stay at five-star hotels with 24-hour luxury service where they can order specialized meals to fit players' dietary needs. If they were to do this for 1,100-1,200 people -- the NBA portion of essential personnel -- it would require roughly 300-350 workers, according to a general manager of a hotel that hosts NBA teams.

If concessions were made -- for example, rooms being refreshed daily but cleaned weekly -- that number could drop by 20%. Having standard meals rather than customized ones could drop it another 10%.

Teams might need to stay in different hotels, or at least on separate floors with dedicated staff, again impacting the number of people inside a bubble.

To be clear: This would require unprecedented work in a tight and uncertain time frame to construct the NBA's path back to live games.

But this is an unprecedented situation. And if the NBA wants to come back this season, this might be its best bet. For now, the NBA does not have a return-to-play plan and remains vague by design, sources said. There are too many questions that remain without answers.

Until the NBA has that certainty, it will continue to wait and see if it can return. So will everyone else.

MORE: Latest updates amid coronavirus suspension