Madison Keys is intent on giving Maria Sakkari a second-round test after marking her first WTA Tour appearance since September with a clinical win at the Qatar Open.

American world number 19 Keys, who reached the US Open final in 2017, had not played on tour since losing to Zhang Shuai in the first round of the French Open in late September – she was ruled out of the Australian swing of this season after a positive coronavirus test.

But Keys roared back to action with a thumping 6-4 6-1 victory over Belinda Bencic on Tuesday, the Swiss who last week reached the Adelaide International final.

"I'm really happy with how I came out and played today," Keys said. "I'm a little bit surprised with myself but hoping to keep the momentum going."

Sakkari promises to pose a tricky test for Keys, who is unseeded this week, given the Greek player dropped only three games in her opening win over Mayar Sherif and has shown bright early-season form.

World number 23 Elena Rybakina tripped up in the first round after the Moscow-born Kazakh player lost 7-6 (9-7) 7-6 (7-5) to Germany's 56th-ranked Laura Siegemund at the WTA Premier event.

Jessie Pegula, Anastasia Pavlyuchenkova, Ons Jabeur and Misaki Doi also scored straight-sets victories in Doha.

At the Lyon Open, French players Caroline Garcia and Kristina Mladenovic were both pushed to three sets before inking their places in the last 16.

Third seed Garcia edged compatriot Oceane Dodin 6-2 2-6 6-3, while fourth seed Mladenovic scrambled for a 5-7 7-5 6-2 win over Romanian Mihaela Buzarnescu.

Former Wimbledon runner-up Eugenie Bouchard, in on a wildcard, was bounced out 7-6 (9-7) 6-2 by Aliaksandra Sasnovich, the world number 96 from Belarus.

Madison Keys is set to miss the Australian Open after testing positive for coronavirus.

The 2017 US Open runner-up announced on Thursday that she contracted COVID-19 before she was due to fly out for the first grand slam of the year.

Keys did not state she will definitely miss the major, which starts on February 8, but it appears the American will not make the trip to Melbourne.

The American wrote on Instagram: "Hi everyone, I wanted to let you know that I unfortunately tested positive for COVID-19 before I was supposed to fly to Australia.

"I'm very disappointed to not be able to play in the coming weeks after training hard in the off-season and knowing Tennis Australia and the tours did so much to make these events happen.

"I am self-isolating at home and will continue to follow all the necessary health precautions. I look forward to being back on tour next month."

It was revealed earlier in the day that three-time major winner Andy Murray has also tested positive for the virus, but still hopes to play in the Australian Open.

Meanwhile, world number 50 Tennys Sandgren was cleared to board a flight from the United States bound for Melbourne despite revealing he returned a new positive coronavirus test this week. 

The American, twice a quarter-finalist at Melbourne Park, initially posted to social media on Wednesday that he had tested positive for the virus for a second time. 

Although his first instance of having the illness was recorded in November, the 29-year-old's participation in the tournament appeared to be in doubt. 

But as he continued to update followers through the day, it emerged he had been allowed to board his flight. 

Players will only be allowed into Australia with proof of a negative test just prior to departure, or with approval to travel as a recovered case at the complete discretion of an Australian government authority.

Anyone wanting to travel out for the tournament who previously tested positive is required to provide additional and highly detailed medical information as proof they are a recovered case and no longer infectious or a risk to the community.