There are just days to go until the start of the Rio Olympics and question marks are still hanging over the event, as organisers scramble to prepare for the "Greatest Show on Earth".

Not everything can be expected to run smoothly and the build-up to the Games is rarely plain sailing. The Olympic Stadium in Athens was only completed two weeks before the 2004 event began, while there were real fears over transport links ahead of the London Games in 2012, which also ended up costing almost four times the initial budget of £2.4bn.

However, Rio has faced more than its fair share of problems:

Zika:

The issue that has generated the most headlines is the spread of the mosquito-borne Zika disease, which can cause birth defects and has been linked to the neurological condition Guillain-Barre. Concerns about the disease have led to competitors including golfers Rory McIlroy, Jordan Spieth and Jason Day to withdrawn from the competition, while long-jumper Greg Rutherford has had his sperm frozen as a precaution in case he is infected.

Around 150 doctors have called for the Games to be postponed or moved, but organisers say the risk to athletes and spectators is very low. They claim that clean-up efforts are going well and that mosquito numbers will have fallen by August.

"We have conducted 44 test events this year, the majority of them in the summer, the peak period for Zika," said the Rio Olympics' chief medical officer in June. "With more than 7,000 athletes, 8,000 volunteers and 2,000 staff participating, there was not a single case of contamination."

However, the disease means Rio is still making headlines for all the wrong reasons.

Sanitation:

Trying to clean up the city has proved an almost impossible task. In a graphic illustration of the problem, late last month, human body parts were washed up close to where beach volleyball teams will be competing.

Most of the problems revolve around sewage, with open-water swimmers and triathletes most at risk. "Scientists have found dangerous drug-resistant 'super bacteria' off beaches in Rio de Janeiro that will host Olympic swimming events and in a lagoon where rowing and canoe athletes will compete," says Reuters.

Several competitors have taken matters into their own hands, reports CNN. "The US Olympic rowing team is taking extra precautions and will be wearing seamless antimicrobial unisuits to compete, while the German sailing team has been practicing trying to sail in trash-coated waters."

Crime:

Rio's crime rate continues to be a cause for concern. The mayor's bodyguard was shot dead in an apparent mugging while off-duty in late June and a doctor was murdered in her car on a main motorway the same weekend. Earlier in the month, members of the Australian Paralympic team were mugged at gunpoint.

June also saw gun battles in the city's slums, as police attempted to recapture suspected drugs trafficker Nicolas Labre Pereira, nicknamed “Fat Family", who was sprung from hospital in a rescue mission that left a patient dead and a nurse and an off-duty policeman wounded.

In fact, there were 2,036 killings in Rio in the first four months of the year.

"An estimated 85,000 police officers and soldiers will be patrolling the streets during the Olympics and Paralympics, but Rio de Janeiro state's acting governor, Francisco Dornelles, says the state is still waiting for 2.9bn Brazilian reals (£660m) from the federal government that is earmarked for security efforts," reported The Independent last month.

Economic crisis:

Compounding the other issues are Brazil's economic problems. Arrivals at Rio's airport have been greeted by striking emergency workers holding a banner reading: "Welcome to hell. Police and firefighters don't get paid, whoever comes to Rio de Janeiro will not be safe."

The country "is suffering the worst recession in decades and Rio's acting governor declared a state of financial disaster... largely to bolster spending on security as the world's spotlight turns to the city," reports The Guardian.

"The recession that saw Brazil’s economy shrink by four percentage points last year has taken a particularly tough toll on Rio. During the boom years, the state awarded billions in tax exemptions to companies ranging from industrial giants to small-scale jewellery dealers, nightclubs, restaurants and love hotels. Tax revenues sunk further with the fall of oil prices that fund much of the state's budget."

Construction:

Just like Athens, Rio faces a race against time to get the venues ready for the start of the Games on 5 August. Organisers are "engulfed in a desperate last-minute building and repair operation as the first of more than 10,000 athletes begin to arrive," says the Daily Mail. "Despite being given seven years to prepare, vital roads, transport and structural work are still to be completed... and the city is littered with Olympic eyesores."

Eleven workers died during construction of Rio Olympic facilities or Games-related projects between January 2013 and March 2016 and in April, two people died when an elevated cycle path, built as an Olympic community project collapsed.

Corruption:

Many of the problems the Rio event faces are related to corruption, which appears endemic in Brazil. In May, investigators widened an Olympic corruption probe to include all the venues and services financed with federal funds. Many of the allegations involve funds earmarked to tackle problems such as pollution and crime, but have ended up lining the pockets of officials and businessmen.

"The Olympics were meant to showcase Brazil's rise as a global power. Instead, they will take place as suspended President Dilma Rousseff faces an impeachment trial, the economy suffers its worst recession since the 1930s, an outbreak of the Zika virus prompts health concerns and a massive corruption scandal infuriates Brazilians," says Reuters.