International rugby star George North is used to getting blows to the head. A member of the Welsh national team as well as the Northampton club, he’s had five of them.

North’s first concussion happened in November of 2014 in Wales’ test match against New Zealand. North was hit so hard he had to come off the field. A few months later, in February 2015, he went down after getting kicked by English rugby player Dave Attwood. He was taken off for a concussion test; eight minutes later he returned to the game, but eventually went down again. This time, he was not taken off by team doctors, but stayed in the game.

The match sparked outrage in the UK. Peter Robinson, father of Northern Irish schoolboy Ben Robinson, angrily compared footage of North to that of his own son Ben. Ben Robinson died after collapsing on his school’s rugby field during a school match.”You do not expect this at elite level, when you think of the back-up and the protocols that at are in place,” he said, according to the BBC. “[North] should have been removed.”

Meanwhile, North kept on playing. In late March of 2015, he took his fifth hit while playing for his domestic team, the Northampton Saints. A photo of him lying unconscious on the field seemed to be a wake-up call for the league. He didn’t play again until Wales’ first World Cup game in September.

Rugby is a sport defined by its physical power. Indeed the hitting—all without a helmet—is a big part of its allure.

Rugby is a sport defined by its physical power. In contrast to its cousin, soccer, rugby has always been synonymous with a very physical kind of toughness. Indeed the hitting—all without a helmet–is a big part of its allure. Take, for example, this YouTube video, “MASSIVE RUGBY HITS – HARDEST MEANEST TOUGHEST – MUST SEE!” which has been viewed over 1.2 million times. We can’t know for sure whether harder hits are helping the sport directly, but they’re certainly not hurting it. Last year’s World Cup in England was the biggest in the history of the sport, selling 2.47 million tickets and generating $300 million in revenue.

“There are a lot of people who say rugby is a totally different game from American football, but the risks may actually be higher in rugby.”

But rugby fans should take heed of the controversy currently raging across the pond in the National Football League (NFL). Where there are hard-hitting players, concussions will soon follow. International rugby leaders needs to start taking a hard look at this issue now, and thinking about solutions. If they wait until the problem becomes a crisis, as it has in the NFL, the sport will suffer. No amount of tackling practice can make the game perfectly safe, and some research suggests that rugby players actually sustain many more hits to the head than football players. “There are a lot of people who say rugby is a totally different game from American football, but my findings show that the risks may actually be higher in rugby,” Doug King, a sports injury epidemiologist at the Auckland University of Technology in New Zealand, told Bloomberg in 2015.

A survey of British players conducted by England Rugby, the governing body of English professional rugby players, showed that 17% of all reported injuries in the 2014-2015 English domestic season were concussions. It’s the fourth successive year that England Rugby recorded growth in that area. The report also showed that “players were at an increased risk of injury following return to play from concussion,” adding that there was a “60% increase in the risk of sustaining an injury (of any type) after returning from concussion compared with those players who had not reported a concussion but other injuries.”

In contrast with American football, rugby players do not typically compete in headgear. Instead, athletes are taught to avoid high tackles and penalized if they try to bend the rules. As Quartz’s Aamna Mohdin noted last year:

Rugby players who tackle above the shoulder risk giving the other team a penalty or being sent off. Instead, players are taught to get low, keep their head behind the ball carrier, hit with their shoulders, and then grasp the ball carrier’s legs and bring them to the ground.

But is it enough? So far, the game’s governing body, the Rugby Football Union (RFU), has insisted that padding need not become a competition requirement. “The scientific and medical research shows that neither padded headgear or helmets are preventative when it comes to concussions,” an RFU spokesperson tells Quartz.

And what about padding for other parts of the body? “The scientific research does not support the theory that additional padding is beneficial in an injury prevention capacity,” the representative says. “However, we continue to research and test ways to ensure players are as safe as possible.”

These efforts have mostly taken the form of outreach. The RFU has provided coaches and officials with an online concussion education service called “Don’t Be a Headcase.” Teams have also been given cards advising what to do if a player seems concussed.

“The scientific research does not support the theory that additional padding is beneficial in an injury prevention capacity.”

At least one team isn’t sure such measures will be sufficient. Saracens, an English club which plays in the Aviva Premiership (the top league of English rugby), recently decided to team up with concussion charity The Drake Foundation to help research concussions. Players will wear impact sensors on their bodies and provide blood samples in an effort to “measure the force and direction of impact to the head,” according to a Drake Foundation press release. It’s a three-year project, so results are unlikely to be available soon.

As Europe starts becoming more aware of the problem, it will be interesting to see what impact—if any—these worries could have on the international growth of the sport. Already popular in the UK, Ireland, Australia, New Zealand, South Africa, France, Fiji and Argentina (amongst other countries), officials have set their sights on the United States’ market share. World Rugby, the game’s governing body, said that participation in the US rose from 5.5 million players in 2012 to 8 million players in 2014. And Forbes noted that there are now “more than 900 men’s and women’s US college rugby programs, all governed outside the NCAA.” Last year, America’s national men’s rugby team, the USA Eagles, even beat New Zealand in the Dubai Sevens tournament, an upset described by some sportscasters as “monumental.”

Could concerns over safety put a damper on rugby’s popularity in the same way they currently threaten to stop the growth of football? Only time will tell. There may in fact not be a totally safe way to play contact sports, especially not as improved training and nutrition create a new generation of bigger, faster athletes. In the short-term, rugby needs to start treating the risks seriously—and fast.

“Concussion used to be almost a badge of honor and a cause for humor,” Dr. Andrew Murray from the Royal College of Physicians and Surgeons of Glasgow, Scotland, told the Financial Times. “But people are recognizing that we only have one brain.”