Japanese tennis superstar Naomi Osaka loses in third round to Marketa Vondrousova

It's Tuesday, Tokyo 2020's fourth official day of competition. The US and Japan are tied for the lead in the gold medal tally, with eight each. Next is China with six and the Russian Olympic Committee with 5. The US has the most medals overall, with 19.

Big-ticket Tuesday: Plenty of major medal events are taking place throughout the day, starting with swimming. America's Lydia Jacoby, Russia's Evgeny Rylov, Australia's Kaylee McKeown and Great Britain's Tom Dean all won gold medals.

The first-ever Olympic surfing competition will conclude later in the day, while at night, Simone Biles and the American women's gymnastic team will look to retain their crown in the team competition.

The full schedule can be found here .

A storm is coming: Tropical Storm Nepartak is expected to make landfall north of Tokyo on Tuesday evening local time, delivering up to 150 millimeters (5.9 inches) of rain to some regions. Tokyo is forecast to get as much as 25 millimeters (1 inch) of rainfall in some areas through Wednesday, along with gusty tropical storm-force winds.

While the storm will be a boon for surfers – the finals were brought forward a day because of the weather – it could put a dampener on other outdoor activities, like archery and softball. However, Nepartak could provide much-needed relief from sweltering heat that has affected athletes at the start of the Games.

Full day for Team USA: The women's gymnastics team is just one of several marquee American teams and athletes competing Tuesday. The US women's softball team will take on host Japan in the gold medal game tonight, and the US women's football team takes on Australia – its first match since opening the tournament with a shock loss to Sweden .

The heavily favored US women's basketball team will also make its Tokyo 2020 debut today, facing off against Nigeria. The Americans, led by US flag-bearer Sue Bird and star guard Diana Taurasi, are going for their seventh straight gold medal. Bird and Taurasi have four gold medals each.

Great Britain makes a splash: British swimmers Tom Dean and Duncan Scott finished first and second respectively in the men’s 200m freestyle – the highest British finish in the event ever. Britain's previous best in the men's 200m freestyle was Robert Crenshaw's fourth at the 1900 Olympics, with compatriot James Guy achieving the same result in the 1916 Games.

Brazil's Fernando Scheffer came in third in Tokyo on Tuesday.

Kaylee McKeown sets a record, then nails her interview: The 20-year-old Australian set the Olympic record for the women's 100m backstroke to win gold, just a month after she set the world record in the same event.

The adrenaline was clearly flowing when she was interviewed by Australia's 7 News after her big win. When asked by the network if she had a message for her mother Sharon and sister Taylor, who were watching, she responded: "“F*** yeah!", before realizing she swore and covering her mouth. Then she followed it up with a celebratory "Woo!"

Her mother jokingly said "I'll have a word to her later," in an interview with 7 News.

Canada's Kylie Masse clinched silver and American Regan Smith took home bronze.

The Russians dethrone the Americans: Russian swimmers Evgeny Rylov and Kliment Kolesnikov finished first and second respectively in the men’s 100m backstroke final – the first time Team USA failed to win gold in the event in more than two decades.

American Ryan Murphy, who won gold in the event at the Rio Olympics in 2016 and holds the world record, collected bronze.

Alaska's first Olympic swimmer wins gold: Lydia Jacoby, 17, was an unexpected winner in the women's 100m breaststroke.

Jacoby is the first-ever Olympic swimmer from Alaska. She went to high school in Seward, a picturesque city in the south of the state with a population of fewer than 3,000 people .

South Africa’s Tatjana Schoenmaker claimed silver, while bronze went to Lilly King of the US.

Competition began at the 2020 Summer Olympics in Tokyo last Wednesday, more than a year after the pandemic delayed the original start date.

But with Covid-19 still spreading in Japan, organizers have been forced to take unprecedented measures to keep competitors and the public safe.

Athletes who contracted the coronavirus have seen their Olympic dreams dashed. Some tested positive in Japan, some before coming.

Here are the athletes who have publicly dropped out due to Covid-19 health and safety protocols.

Team USA:

• Bradley Beal – Men’s basketball (Placed in health and safety protocol but hasn’t publicly disclosed a positive Covid-19 test)
• Taylor Crabb – Men’s beach volleyball
• Kara Eaker – Women’s gymnastics
• Coco Gauff – Women’s tennis
• Katie Lou Samuelson – Women’s 3x3 basketball
• Bryson DeChambeau — USA Golf

Team Czech Republic:

• Barbora Hermannova – Women’s beach volleyball (Ruled out because her partner Sluková-Nausch tested positive for Covid.)
• Simon Nausch – Coach, women’s beach volleyball
• Ondrej Perusic – Men’s beach volleyball
• Michal Schlegel – Men’s cycling
• Pavel Širuček – Men’s table tennis
• Markéta Sluková-Nausch – Women’s beach volleyball

Team Great Britain:

• Dan Evans – Men’s tennis
• Amber Hill – Women’s shooting
• Johanna Konta – Women’s tennis

Team Mexico:

• Hector Velazquez – Baseball
• Sammy Solis – Baseball

Team Netherlands:

• Finn Florijn – Men’s rowing
• Candy Jacobs – Women’s skateboarding
• Reshmie Oogink — Taekwondo

Team South Africa:

• Kamohelo Mahlatsi – Men’s football
• Thabiso Monyane – Men’s football

Team Australia:

• Alex de Minaur – Men’s tennis

Team Chile:

• Fernanda Aguirre – Women’s taekwondo

Team Portugal:

• Frederico Morais – Men’s surfing

Team ROC (Russian Olympic Committee):

• Ilya Borodin – Men’s Swimming