- Coronavirus pandemic
image copyrightGetty Images
Final preparations are being made ahead of Friday's opening ceremony of the Tokyo Olympic Games.
Organisers have repeatedly insisted the competition can be held safely, despite calls for it to be cancelled over coronavirus concerns.
However, the head of the Tokyo 2020 organising committee has said he is monitoring infection numbers closely, and would hold "discussions" on the Games' future if necessary.
When are the Olympics and Paralympics?
Officially, the 2020 Summer Olympic Games take place between 23 July and 8 August, but the first events have already begun.
The Paralympic Games are due to run between 24 August and 5 September.
The Games were postponed from last year because of Covid.
The Olympics will feature 33 sports at 339 events across 42 venues. The Paralympics will feature 22 sports at 539 events across 21 venues.
Most events are in the Greater Tokyo area, although some football games and the marathon will take place in the northern city of Sapporo.
- Tokyo 2020 Olympics day-by-day guide
- What's new at Tokyo 2020?
What's happening with Covid in Japan?
Overall the country has had relatively low case numbers, but a new wave of infections began in April.
As of 21 July, there were 848,222 confirmed cases and 15,062 deaths (compared with 5.5 million cases and 128,800 deaths in the UK).
Japan only began vaccinating people in February, later than most other developed nations. Only 22% of Japan's population of nearly 126 million people is fully vaccinated.
In Tokyo and Osaka, the two cities hit hardest by the recent surge, authorities hope over-65s will be fully vaccinated by the end of July.
Entry to Japan by foreigners from 159 countries – including the UK – is currently banned.
- Japan's battle to contain Covid before the Olympics
image copyrightReutersimage captionThe vaccination programme started relatively late in JapanWhat Covid measures will be in place for visiting athletes?
International athletes and support staff are being tested before departure and on arrival in Japan.
UK athletes are required to stay within their Team GB bubble for at least the first three days in the country. They will be tested every day.
Athletes don't have to be vaccinated, though International Olympic Committee (IOC) officials expect around 80% will be.
A Chilean taekwondo athlete became the first Olympian to be ruled out of action on 21 July, after testing positive for Covid.
More than 70 people associated with the Games have so far tested positive for the virus, including British athlete Amber Hill who has withdrawn from the women's skeet competition.
Will there be any spectators?
Ministers decided to ban all spectators from the Olympics after a state of emergency was declared in Tokyo on 8 July.
The state of emergency was in response to a spike in Covid cases. It will stay in place until 22 August.
It was previously announced in March that international fans would not be able to attend the games, but up to 10,000 Japanese spectators were due to go.
image copyrightGetty Imagesimage captionTeam GB opened the football competition against Chile in an empty stadium on Wednesday
A decision about whether Japanese spectators will be able to attend the Paralympics has not yet been made.
Tokyo 2020 President Seiko Hashimoto said she was "sorry to those who purchased tickets and everyone in local areas".
Could the Games be cancelled?
The contract between the IOC and the host city Tokyo suggests only the IOC can cancel the event.
The IOC is thought to make around 70% of its money from broadcast rights, and 18% from sponsorship.
It has repeatedly insisted the Games can go ahead safely, even under a state of emergency.
IOC president Thomas Bach said the thought of rescheduling the competition "caused sleepless nights", but insisted that the Games must go ahead "to give hope" for the future.
The head of the World Health Organization, Dr Tedros Adhanom Ghebreyesus, also backed the competition, arguing it could show what can be done with the correct Covid safeguards.
But the head of the Tokyo 2020 organising committee Toshiro Muto has not ruled out cancelling the Olympic Games even at this late stage.
He said he would keep an eye on infection numbers and hold "discussions" if necessary.
If the Tokyo organisers were to cancel the contract, the risks and losses would probably fall on the Japanese side.
The budget for Tokyo 2020 was set at $12.6bn (£8.9bn), although it's been reported that the actual cost may be double that.
Do people in Japan want the Olympics?
Several towns set to host athletes reportedly pulled out earlier in the year because of fears about Covid and extra pressure on the healthcare system.
In May, a Japanese doctors' union said it was "impossible" to hold the Games given the pandemic.
A poll in May in the leading Asahi Shimbun newspaper suggested more than 80% of the population want them cancelled or postponed.
The paper also called for the event to be cancelled.
image copyrightPhotoshotimage captionMany people in Japan are against the OlympicsWhat have athletes' representatives said?
A number of bodies have expressed concern.
The World Players Association, representing 85,000 athletes in over 60 countries, said the IOC must do more to ensure athletes' safety – with stricter physical distancing and more rigorous testing.
Japanese athletes have largely kept a low profile, but the country's biggest sports star, tennis champion Naomi Osaka, previously said there should be a debate about whether the Games should go ahead.
media caption'If people are not feeling safe, then it's a really big cause for concern'