LONDON — Doping scandals. Bribery allegations. Fears about Zika. Political, economic and corruption crises.

What else could go wrong?

The past few days have unleashed a wave of grim news for the Olympics, battering four host cities – past, present and future – on three continents, and further eroding public trust in the credibility of the global sports movement.

The 2014 Winter Games in Sochi, Russia, the upcoming Olympics in Rio de Janeiro, the 2018 Winter Games in Pyeongchang, South Korea, and the 2020 Summer Olympics in Tokyo all have been caught up in an unprecedented meltdown of trouble.

Just when the sports world thought it had pulled away from the darkest days of the FIFA and IAAF scandals, a confluence of turmoil this week brought the clouds back and threatened the image and prestige of the Olympics, less than three months before the Aug. 5 opening ceremony in Brazil.

It poses a new test for the International Olympic Committee, which endured its worst crisis with the Salt Lake City bidding scandal in the late 1990s.

Richard Ings, former chief executive of Australia’s anti-doping agency, said sports leaders must work quickly or “sink further into this quicksand.”

“It’s about sport and the credibility of sport,” he said. “And the responsibilities rest with sports administrators who are failing to reform.”

A look at the chaos across the Olympic world:

SOCHI SCANDAL

The 2014 Games were attacked by critics for a reported $51 billion price. Now they may be remembered for one of the biggest sporting frauds ever exposed. The former head of Moscow’s anti-doping lab, Grigory Rodchenkov, detailed in The New York Times how Russia operated a state-sponsored scheme that included exchanging bottles of tainted urine samples for clean ones through a concealed hole in the wall of the Sochi lab.

The doping program reportedly involved at least 15 Russian medalists. On Friday, President Vladimir Putin’s spokesman denounced Rodchenkov’s claims as “turncoat’s libel.”

The IOC said it “will not hesitate to act decisively to punish those responsible.” If the cheating is proven, it could result in mass disqualifications and stripping of medals. The Sochi Olympics, one of Putin’s pet projects, could wind up as Russia’s Shame Games.

The new doping allegations won’t help Russia’s case for having its track and field athletes reinstated for Rio. They were suspended by the IAAF following a WADA report that found state-sponsored cheating. Pressure also mounted on Kenya – and its celebrated distance runners – when the African nation was declared non-compliant Thursday with WADA’s rules.

BLAME IT ON RIO

Never has a host nation been in such political and economic turmoil before an Olympics. Seven years ago, when the IOC picked Rio de Janeiro to host South America’s first Olympics, Brazil was a rising star on the world stage. Now, 84 days before the games begin, the country is in its worst recession since the 1930s. It is torn by a massive corruption scandal centered on oil giant Petrobras. Olympic budgets have been slashed.

The political situation has imploded, with the Senate voting Thursday to impeach President Dilma Rousseff. She won’t be declaring the Olympics open on Aug. 5. Her vice president, Michel Temer, is interim president.

While most of the Olympic venues are ready, concerns remain over the severe water pollution at the sailing and rowing sites.

If all that wasn’t bad enough, Brazil is in the grip of the Zika virus. The IOC and World Health Organization said the games will be safe, while urging visitors to take precautions.

PYEONGCHANG’S PROBLEMS

The first Winter Olympics in South Korea have been dogged by more problems than expected, including construction delays, conflicts over venues, a shortage of local sponsors – and a revolving-door leadership. While preparations for the 2018 games seemed to accelerate after successful test events this winter, the local organizing committee was hit by yet another sudden resignation of its top leader. For the second time in less than two years, there has been a change at the helm.

Cho Yang-ho stepped down to focus on dealing with troubles at the family shipping company. Cho had taken over in July 2014 after the resignation of Kim Jin-sun, the former governor of the Pyeongchang region. On Thursday, Pyeongchang elected former South Korean government minister Lee Hee-beom as the new organizing committee chief. With less than two years to go until the games, Lee will need to get up to speed – fast.

TROUBLE IN TOKYO

Tokyo, seen as a safe choice three years ago, has been buffeted by problems. The original stadium design was scrapped because it was too expensive. The original logo was dumped after allegations it was copied from a Belgian theater.

But this week brought the most damaging setback yet: allegations of possible bribery during Tokyo’s winning bid.

French prosecutors said Thursday they had widened their inquiry to look into payments of $2 million from a bank in Japan to an account in Singapore in the months before and after Tokyo won the games.

The account was tied to the son of disgraced former IAAF President Lamine Diack. Both Diacks are under investigation in France on corruption charges.

Tokyo bid leaders issued a statement Friday insisting the payments were for legitimate consulting fees.