Jamaican sprint queen Shelly-Ann Fraser-Pryce will make her grand entrance at the Tokyo Olympics as coronavirus concerns loom over the start of the athletics programme on Friday.
The reigning 100m champion will launch her bid to become the first woman to win an individual Olympic athletics event three times when she headlines competition at Tokyo's Olympic Stadium.
A new champion will be crowned in the men's 10,000m, after Britain's 2012 and 2016 winner Mo Farah failed to qualify, and US great Allyson Felix will figure in the heats of the inaugural 4x400m mixed relay.
Competition gets under way in the fan-free, 68,000-capacity stadium a day after a Covid-19 scare forced Australia's athletics team into temporary isolation in the Olympic Village.
Although most were soon released, three of the Aussie contingent remain in isolation as close contacts of US pole vaulter Sam Kendricks, who tested positive for Covid-19 and was ruled out of the Games.
Shortly after Kendricks' case emerged, Argentine pole vaulter German Chiaraviglio revealed he had also tested positive and would not take part in the Games.
The incident was a jolting reminder of the perils facing athletes at the Tokyo Games, where their Olympic dreams are at risk of being dashed at any moment.
"We knew this Olympic game was different and with different rules, and here I am, it's my turn," Chiaraviglio, 34, wrote on Instagram.
"Living through this is very difficult, but it will also pass," he added.
The men's 10,000m, the only final on day one of the athletics, could be a showdown between two Ugandans: world record-holder Joshua Cheptegei and world-leader Jacob Kiplimo.
Commonwealth champion Cheptegei, who finished sixth in Rio before winning world silver in 2017 and gold in 2019, and Kiplimo are both aiming for the 5,000m-10,000m double in Tokyo.
Norwegian Karsten Warholm and American rival Rai Benjamin line up in the men's 400m hurdles heats while Felix, 35, opens her fifth and final Olympics in the mixed relay preliminaries.
Meanwhile in the pool, Emma McKeon and Cate Campbell can continue Australia's gold rush in the women's 100m freestyle, and Russia's Evgeny Rylov will look to add 200m backstroke gold to his 100m title.
French judo star Teddy Riner is bidding to become the first man to win three consecutive heavyweight titles, and Marin Cilic and Ivan Dodig take on Nikola Mektic and Mate Pavic in an all-Croatian men's doubles final.
Day seven also features gold medals in badminton, canoe slalom, fencing, rowing, shooting, table tennis and trampolining.
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