The ever-increasing popularity of the Las Vegas Sevens is helping rugby to become one of the fastest-growing sports in the United States. Ethan Miller/Getty Images North America/Getty Images/file

The Las Vegas Sevens is always a fan favorite, but the two recent editions have been particularly special with USA winning back-to-back title Brandon Magnus /Getty Images North America/Getty Images

The 2017 event attracted record crowds to Sam Boyd Stadium for the seventh consecutive year with an attendance of 80,691 across the three days. Ethan Miller/Getty Images North America/Getty Images/file

Like many sevens events around the world, Vegas inspires a party atmosphere with spectators coming in fancy dress. MARK RALSTON/AFP/AFP/Getty Images

The 2017 attendance was a slim increase on the previous year, which brought in 80,138, including these fans dressed as Elvis Presley. MARK RALSTON/AFP/AFP/Getty Images/file

The USA has enjoyed its best start to a sevens season this year, finishing runner-up at the first four tournaments. MARK RALSTON/AFP/AFP/Getty Images/file

Over 100,000 fans attended the Rugby World Cup Sevens in San Francisco, the best-attended rugby event ever in the USA. MARK RALSTON/AFP/AFP/Getty Images

In common with rugby's US sports rivals, cheerleaders play a big part in the entertainment schedule at Vegas -- which over the years has included Cirque Du Soleil and fighter jets. Here members of the USA Sevens Sweethearts perform during the 2015 tournament. Ethan Miller/Getty Images North America/Getty Images/file

The 2016 tournament was broadcast on NBC and its Sports Network. It reportedly reached national and international audiences in over 400 million homes and 147 countries. Here a Samoan rugby fan supports his team in 2016. MARK RALSTON/AFP/AFP/Getty Images/file

A security guard chases a costumed fan after she ran on the pitch during the 2015 Cup Final match between Fiji and New Zealand. Ethan Miller/Getty Images North America/Getty Images/file

It required two guards to finally bring the woman to the ground. Ethan Miller/Getty Images North America/Getty Images

Security was busy that day, as this fan also invaded the pitch before Fiji beat New Zealand. It was the All Blacks' fourth successive defeat in Vegas finals. Ethan Miller/Getty Images North America/Getty Images/file

This fan also took center stage during a 2014 match between the US and Spain. Ethan Miller/Getty Images North America/Getty Images/file

Players get close to the crowds in Vegas. Here members of the Canadian team pose with fans following a 2014 match against Samoa. AFP/AFP/AFP/Getty Images/file