South Africa's Caster Semenya set the year's best time in the 800m at the Diamond League meeting in Eugene as American sprinter Christian Coleman suffered a surprise defeat in the 100m.
Semenya claimed victory in a time of one minute 55.91 seconds.
World indoor 60m record holder Coleman, making his 2018 outdoor debut, finished second to compatriot Ronnie Baker, who won in a wind-assisted 9.78.
Britain's Reece Prescod finished third in 9.88 and CJ Ujah came sixth.
If Prescod's time had been legal it would have been within 0.01 seconds of Linford Christie's long-standing British record.
Marie-Josee Ta Lou won a high-class women's 100m, coming from behind to beat fellow Ivorian Murielle Ahoure in a wind-legal 10.88.
Olympic champion Elaine Thompson of Jamaica took third with 10.98 while British record holder Dina Asher-Smith posted her best 100m time since 2015 to finish sixth in 11:06.
Britain's Laura Muir, who completed her veterinary degree this week, was second in the women's 1500m behind surprise winner Shelby Houlihan from the USA, while team-mate Laura Weightman came 12th.
British world indoor champion Andrew Pozzi battled food poisoning to finish seventh in the 110m hurdles and compatriot Holly Bradshaw came eighth in the pole vault.
There were impressive wins for American pair Noah Lyles (200m) and Shaunae Miller-Uibo (400m).
Lyles stormed away to win in 19.69 and equal South African Clarence Munyai's world-best time for 2018, with Britain's Nethaneel Mitchell-Blake clocking 20.51 for fifth.
Miller-Uibo, the Olympic champion, clocked 49.52 for a comprehensive victory over world champion Phyllis Francis (50.81).
The head of African athletics says the continent will bid to host the 2025 World Championships.
Africa has never staged the biennial event, which started in 1983, despite being home to many world champions.
Hamad Kalkaba Malboum says he believes a bid is set to come from one of six African nations.
"We are talking with Kenya, South Africa, Nigeria, Algeria, Egypt, Morocco - those countries have the facilities," said the Cameroonian.
"I have very positive sounds from some of them," added the president of the Confederation of African Athletics (CAA).
Morocco is the only African country to have staged a leg of the Diamond League, the annual athletics series which runs from May to September around the world.
The Moroccan city Casablanca was also the last in Africa to try to stage the World Championships, having bid unsuccessfully for the 2011 event.
Kalkaba pointed to recent successes with March's World Cross Country Championships in Uganda and July's World U18 Championships in Kenya as reasons to be hopeful.
"People said that Africa could not host the World Cup in football, but we did it very successfully," he added in reference to South Africa's staging of the 2010 finals.
Kalkaba, who took charge of the CAA in 2003, said the president of athletics' governing body - the IAAF - backs the idea.
"President Coe is supporting the fact that Africa could host the World Championships," said the 66-year-old, an IAAF vice-president himself.
With the 2019 and 2021 events having been awarded to Qatar and the United States respectively, the next available championship to bid for is 2023.
Yet Kalkaba, who has been in talks with political leaders including Kenyan President Uhuru Kenyatta, believes this is too early for the continent.
He said Africa has never previously staged the biennial competition because athletics was less popular than football and also "because we are facing many other social problems - health, education, building roads or railways - political leaders are sometimes afraid of spending a lot of money on hosting an event.
"But I think many now realise that [staging the championships] could put the nation on the world map in terms of publicity and promote tourism so there is a benefit from hosting the event. This was not the case in the past."
A decision on who will stage the 2025 finals is set to be taken in 2020.
Former Olympic 400m champion Sanya Richards-Ross says she has helped other women by speaking publicly about having an abortion.
Richards-Ross, 32, revealed in her new book that she had a termination a day before leaving for Beijing 2008, where she won a gold and bronze medal.
She later claimed that every female athlete she knows has had an abortion but the issue is "not talked about".
"There is a brokenness there," the American told BBC Radio 5 live.
"For me, it was really healing to be able to share that with other friends.
"Now I've had other women reach out to me, not just in track and field but all over the world. They've said 'your courage is helping me to heal myself'. That's meant a whole lot to me.
"I feel bad because I think people misinterpreted when I said 'everyone I know'. I don't intimately know a lot of women in this sport.
"When I started to share my story I was like 'wow', so many women around me have been through the same thing and no matter how close you are, it's something that people don't share."
Richards-Ross won three Olympic golds in the 4x400m relay for the USA, with her first and only individual gold coming in the 400m at London 2012.
She also claimed seven medals at the World Championships - including five golds - before retiring in 2016.
During her career, the Jamaican-American athlete became well-known for her style on the track - which included wearing make-up and nail varnish while competing.
She hopes that her image, as well as her sporting achievements, will inspire female athletes in the future.
"People ask me 'why do you wear make-up when you run?' and 'why are you so stylish?' and a big part of it for me was to show young girls that you don't have to be butch or masculine to be a great athlete," she said.
"I've had so many girls during my career saying 'thanks for making it cool to wear make-up on the track'. My hope is that I've empowered some young women to go towards sports because sport is one of the best life teachers you can have."
Usain Bolt said he was "saying goodbye to everything" and "almost cried" as his successful career came to a close at the World Championships in London.
Eight-time Olympic gold medallist Bolt, 30, is retiring from athletics having illuminated the sport like few others.
"It's really sad that I have to walk away now," said the Jamaican, who completed a lap of honour of London Stadium on Sunday's closing night.
"I was saying goodbye to the fans and saying goodbye to my events also."
When asked if he would consider a return to racing, he replied: "I've seen too many people retire and come back just to make it worse or to shame themselves.
"I won't be one of those people."
Bolt could only manage bronze in his penultimate race - the men's 100m – before pulling up injured just as he began to hit top speed in his final event, the 4x100m relay, on Saturday night.
It meant the 19-time global champion, recently described by Lord Coe as “a genius” akin to boxing legend Muhammad Ali, bowed out in unfamiliar fashion - helped off the track by his team-mates, barely able to stand upright.
"For me, I don't think one championship is going to change what I've done," he added.
"I remember after losing the 100m, someone said to me, 'Usain, no worries, Muhammad Ali lost his last fight also, so don't be stressed about that'.
"I've proven myself year in, year out, throughout my whole career. I was saying goodbye to everything. I almost cried. It was close, but it didn't come."
Botswana will hold a national holiday in honour of Isaac Makwala if he wins 200m gold at the World Championships.
Makwala, whose exploits in London have been a major talking point this week, races in the final later on Thursday.
On Tuesday he was barred from the 400m final, as officials tried to halt a "very virulent" norovirus outbreak.
But he returned and progressed from an individual 200m time trial on Wednesday - he was quarantined for Monday's heats - and celebrated by doing press-ups.
The 30-year-old, who said he is "still running with a broken heart" will be going up against South Africa’s Wayde van Niekerk, who on Tuesday dominated the 400m race for which Makwala said he had been training.
Botswana's Sports Minister Thapelo Olopeng told BBC Sport the country would also pay Makwala the $10,000 (£7,500) he would have received from the government had he won 400m gold.
"The president has set aside a certain day for him," said Olopeng. "It will be a public holiday for people to come and meet Makwala and all over the country there will be celebrations with music and dancing. The man has lifted the name of our country higher and higher, and he deserves this welcome as our hero."
The minister said that the country had submitted a further complaint about the handling of the issue by the International Association of Athletics Federations (IAAF), the world governing body.
"The way he performed yesterday [in the 200m qualifiers] he showed no signs of ailment and I don't understand why the IAAF has continued with the same decision," Olopeng said.
"They should call for a re-run or give him the same opportunity as they did in the 200m [a time-trial run on his own]. They have not responded and if they don't then we will take the matter forward, we have a legal team waiting to give us advice on how far we can take it.
"What happened to our athlete has created a lot of displeasure in the country and we are very unhappy. To me it's a great disappointment."
The IAAF - criticised for its decision to stop Makwala running in the 400m final - allowed him another chance to compete in the 200m after receiving a written request from the Botswanan federation.
Makwala, who qualified second fastest behind the United States' Isiah Young, has the quickest season's best and personal best of the nine-man field.
Van Niekerk, running his fifth race in as many days, only made it through as a fastest loser.
Meanwhile, the number of people associated with the World Championships who have reported illness has risen from 30 to 40, Public Health England announced.
The body said that three cases have been confirmed as norovirus by laboratory testing.
The IAAF defended its actions and said it was under instruction to quarantine athletes who showed symptoms of the virus.
It acknowledged Makwala's absence was "a sad case" but said its medical staff examined the athlete and notes taken by a doctor showed he had been vomiting over an 18-hour period.
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