LONDON (AP) — The Latest from the world championships (all times local):
British health authorities say about 50 people linked to the world championships have reported being ill with a stomach virus.
Dr. Deborah Turbitt of Public Health England says four cases have been found by laboratory testing.
Early this week, the figure stood at about 30 people.
Botswanan sprinter Isaac Makwala missed the 400-meter final because of the virus, but he returned to run in the 200.
Olympic champion Caster Semenya is into the final of the 800 meters at the world championships, and will be the favorite for another gold.
The South African, who won her first world title eight years ago, took the lead on the final bend and was in control from then on. She had the top qualifying time of 1 minute, 58.90 seconds.
Ajee Wilson of the United States won the first heat ahead of Melissa Bishop of Canada to go through to Sunday's final. Francine Niyonsaba of Burundi and Margaret Wambui of Kenya were automatic qualifiers from the third semifinal heat.
Sally Pearson is back.
The former Olympic champion from Australia missed much of the past two seasons because of injury, but she produced the fastest time to win her 100-meter hurdles semifinal heat at the world championships.
Pearson won her heat in 12.53 seconds, .24 seconds faster than Nia Ali of the United States.
Defending champion Danielle Williams of Jamaica hit the first hurdle in her semifinal heat and never recovered. She finished fifth behind winner Christina Manning of the United States and failed to qualify for the final.
World-record holder Kendra Harrison also hit the first hurdle and missed out on the two automatic places. But her strong recovery allowed her to just make the final on time. Since former champion Dawn Harper Nelson won the heat, the Americans have four in the final and could sweep the medals again — like they did last year at the Rio de Janeiro Olympics.
Kevin Mayer of France extended his lead in the decathlon with yet another strong showing, this time in the high jump, with only one event remaining in Friday's program at the world championships.
Mayer jumped 2.08 meters, just a centimeter short of his outdoor best, to reach 3,581 points. The Olympic silver medalist now leads Kai Kazmirek of Germany, who topped the high jump by clearing 2.11 meters, by 109 points.
Another German, Rico Freimuth, fell back to third place with a disappointing jump of 1.99 and has 3,472 points.
Two-time world champion Trey Hardee of the United States has 3,441 points in fourth.
Olympic silver medalist Kevin Mayer of France took the lead in the decathlon after three events at the world championships, relying on strong performances in the 100 meters and the shot put.
Mayer has 2,703 points, 25 more than Rico Freimuth of Germany. Two-time world champion Trey Hardee of the United States is in third place with 2,647 points.
The decathletes return in the evening session for the high jump and the 400 meters before competing in the five other events on Saturday.
Rico Freimuth took the early lead in the decathlon at the world championships.
The German was second in the 100 meters and then placed seventh in the long jump to take the lead with 1,898 points.
Damian Warner of Canada and Karl Robert Saluri of Estonia were three points behind in a tie for second.
Olympic silver medalist Kevin Mayer of France is fourth with 1,869 points, while two-time world champion Trey Hardee is sixth with 1,847.
World-record holder Kendra Harrison led a strong U.S. contingent into the semifinals of the 100-meter hurdles at the world championships.
Harrison had the top time in the opening heats in 12.60 seconds, .06 seconds ahead of defending champion Danielle Williams of Jamaica. Another heat winner was former Olympic and world champion Sally Pearson of Australia, who had the third-best time of 12.72.
Christina Manning, Dawn Harper Nelson and Nia Ali also went through to make it four Americans in the semifinals.
Deborah John of Trinidad and Tobago went down hard in the fifth heat and had to be stretchered off the track.
Olympic champion Sandra Perkovic of Croatia and defending champion Denia Caballero of Cuba both reached the final of the discus by throwing beyond the automatic qualifying mark at the world championships.
With the target set at 62.50 meters, Perkovic had a massive second throw of 69.67 to go into Sunday's final. Caballero had a mark of 63.79.
Kevin Mayer of France, the Olympic silver medalist in Rio de Janeiro, got off to a strong start in the decathlon with a lifetime best of 10.70 seconds in the 100 meters.
Trey Hardee, the last gold medalist before Aston Eaton took over the event at the 2012 London Olympics, finished his heat in 10.75 seconds, way off the 33-year-old veteran's best time.
Leading after the opening event at the world championships was Damian Warner of Canada. He ran 10.50 seconds, also far below his best, despite a rare sunny morning at the Olympic Stadium.
Rico Freimuth of Germany had the second best time of 10.53.
The decathletes will next head to the long jump, the second of the 10 events.
The two-day competition in the decathlon set off under sunny skies at the Olympic Stadium with Kevin Beyer and Trey Hardee favorites for gold at the world championships now that Ashton Eaton has retired.
Eaton won the last two world championships and Olympics, dominating the 10-event competition as much as Usain Bolt did the sprints. Now the race to become the "world's greatest athlete" is wide open.
The decathlon starts out with the 100 meters, followed by the long jump and the shot put.
Later Friday, there will be finals in the women's 200, steeplechase and long jump, and the men's hammer throw.
More AP track coverage: https://www.apnews.com/tag/London2017