Bob Jungels of AG2R Citroen tested positive for COVID-19 on Wednesday, tested positive for COVID-19 on Thursday, and started the Tour de France on Friday.

While these facts may seem shocking at first glance, Jungels, who is from Luxembourg, did not violate any rules, nor did this happen because the sport's governing body, the UCI, relaxed its rules.

In fact, the UCI approved not only the race organizers, but also Jungels' own team, for Jungels to participate.

In contrast, a number of riders, including Tim DeClercq and Matteo Trentin, were removed from the start list after testing positive. So why are athletes who test positive for COVID-19 allowed to compete in bicycle races?

The answer lies in something called the CT (short for Cycle Threshold) score, a PCR test performed by a device that sweeps out viral particles while circulating a sample. The longer it takes to find the virus, the higher the CT score and the lower the amount of virus. The fewer cycles it takes to detect the virus, the lower the score and the higher the viral dose.

This method is a more accurate way to determine a person's infectivity than a simple "double line" or blurred line analysis in an antigen test.

"What is important is the threshold for infectivity," Dr. Thomas Klimaschka of AG2R Citroen told Cycling News. 'If your score is above 30, you are extremely unlikely to be infectious; if your score is above 35, you are not.'

"In the old days, antigen testing did not catch people who scored over 30. Today, one-third of cases are detected between 30 and 35 years of age, but even then, a 35-year-old antigen test will never be positive."

Jungels' score on Wednesday "was close to 30. On Thursday, he said his score was 38.

For Klimaschka, it was important to be able to compare the two numbers. As with the biological passport, he was able to plot the "journey" of the virus and determine that Jungels' viral load was decreasing and not the other way around.

"With one value you don't know if it comes from the top or the bottom. We don't know if it's going to move.

"If the scores keep going down, he has to get out of the race. But in Bob's case, it went straight up to 38 points.

The UCI declined to comment when contacted by Cycling News; on the UAE Team Emirates bus, Dr. Adriano Rotunno supported this theory.

"Viruses are mysterious; PCR tests can be positive weeks or months after infection; PCR tests can pick up old viruses, called viral ghosts. Even if you have an old virus, it's not infectious, but because the PCR is positive, people will think, 'This person is positive.'"

Nevertheless, Rotunno pointed out that the CT score is only one piece of the puzzle, which includes the rider's clinical condition.

"You have to take clinical pictures, check for any abnormalities in the body, check for fever, check for heart activity if possible. And if everything checks out and you are medically healthy, you are not infectious and safe to ride, despite the positive PCR test."

AG2R's physician confirmed that Jungels had not undergone cardiac screening.

Earlier this week, things got bogged down when the UCI released the latest version of the COVID-19 protocol. Released under the guise of tightening regulations amid the new COVID-19 wave, it was undoubtedly watered down, and the biggest development was that teams with two riders testing positive no longer had to send their entire team back home.

This new regulation was seen by some as a loophole, allowing riders who tested positive the possibility of competing in the race. However, there were no substantive changes in this regard.

The protocol published in January and updated last week stated: "If a PCR test is positive during a stage race, the rider or staff member concerned will be excluded from the event. However, an exemption may be granted if the UCI Medical Director, in coordination with the Covid Doctor of the event, can demonstrate to his satisfaction that the rider or staff member in question does not have an infectious disease and is not likely to transmit it to third parties."

What is different with respect to the GranTur is the decision-making process in the event of a positive case. Previously, the decision was left to the UCI. Now it is "decided by a majority of the panel" consisting of the race doctor, the UCI medical director, and the doctor of the team concerned.

"As far as I know, they haven't really changed anything," Klimaschka said.

Rotunno added, "Since COVID-19 came out, there have been tripartite consultations. That's best practice. I don't know if it's a vote or not. It could be, but in general it won't be a big discussion."

In addition, "I don't think it will be a big discussion.

In Jungels' case, he tested positive before the race, not during the race. The rules require a negative test (now antigen, not PCR) "within two days" to enter the race bubble. Jungels missed the national championship road race last Sunday due to an upset stomach.

After traveling to Copenhagen on Tuesday, Jungels was quarantined after testing on Wednesday and joined his teammates after the all-clear on Thursday evening.

Klimaschka noted that if he tested positive while the race was underway, it would make it less likely, but not impossible, for him to continue.

Theoretically, an athlete could be infected with COVID-19 and recover to the point of testing positive with a very high CT score on a rest day. However, the UCI "strongly recommends" antigen testing "daily, if possible, and at least every two to three days."

According to Lotuno, this rule creates a small but gray area.

"It is not always black and white, but it is generally a logical decision. It can be abused, but you would want to check all the boxes to proceed safely."

UAE Team Emirates experienced a unique case in the days before the Tour when Matteo Trentin tested positive and was replaced by Marc Hirschi. In this case, Trentin's CT score was "very low," meaning that his COVID-19 load was high and infectious.

"It would have been a risk to himself, his own health, his team, and the cycling community. We could not ethically allow this athlete to compete in the race. It's not appropriate medical practice. That's why we pulled him out."

The Tour de France had 176 riders start the race; another change to the UCI's COVID protocol was the introduction of antigen testing on rest days, as opposed to PCR testing. If the result of the antigen test is positive, the affected person must undergo PCR testing.

The first rest day on Monday is likely to be a nerve-wracking one for many players due to the number of positive results in the pre-tour testing.