Much like Usain Bolt at his best, Van Niekerk can cruise even against the best in the world.
Van Niekerk was joined in the semis by team-mate Akani Simbine, a 100m finalist. Steven Gardiner, 21, of the Bahamas was a clear second in 44.41 and 20-year-old world junior champion Abdalelah Haroun of Qatar blasted through at the end to snatch bronze in 44.48.
In the other lane, van Nierkerk, the world record holder for 400m with the 43.03 he ran at the Rio Olympics, is the only man in history to go sub-10, sub-20, and sub-44. "It is a blessing".
"I was hoping for more improvement but when I try to improve too hard, my technique is not good". I wish to thank the IAAF for giving me another chance and the crowd is so wonderful.
"I'm very excited for the 200m". Suddenly athletics had found its new superman - for one night anyway.
For a man who is widely regarded as one of the most talented athletes of his generation, Wayde van Niekerk is curiously humble, nearly self-deprecating.
Tower Hotel, used annually as the base for the London Marathon, said in a statement: "We have worked collaboratively with the EHO (Environmental Health Officer) and the IAAF to investigate the origins of the illness and can confirm that the hotel was not the source".
It issued a statement saying it regretted the situation, but said it had acted on the advice of health authorities.
"The elephant in the room is that Wayde van Niekerk is an IAAF favourite, a fan favourite, he's a favourite of everyone", he said.More news: Trump warns North Korea of 'fire and fury'
South African Wayde van Niekerk won gold in the 400m at the World Athletics Championships in London yesterday, but the real drama occurred away from the track as one of his main rivals accused the organisers of "sabotage" after banning him from the stadium.
Bolt can still move to 15 with a medal in the 4x100 relay this weekend, but Felix might run on both relay races for the USA team, which could bring her to 16. "Conspiracy theories are going round".
In front of another capacity crowd at the London Stadium, a brilliant pole vault competition won by USA's Sam Kendricks and the 800m victory of France's Pierre-Ambroise Bosse also helped light up a cold night. "It was a never ending nightmare".
"But from endurance I go straight to speed tomorrow".
In incredible scenes at the London Stadium tonight, the star athlete dropped to the track and did several press-ups before crossing the line. I was not tested for that.
"[Over] the last few metres I ... looked up to the screen and I noticed how far ahead I was. People can forgive me now because I now have that world title".
The Bahamian Olympic champion's loss was Phyllis Francis' gain as the American crossed the line first to muted celebrations.
Conseslus Kipruto maintained Kenya's fine record in the men's 3000 metres steeplechase winning in cheeky style from Morocco's Soufiane El bakkali with long-time leader Evan Jager of the United States third.