Brazilian President Dilma Rousseff and International Olympic Committee (IOC) President Thomas Bach attended an official countdown ceremony on 5 August, marking one year until the opening of the Rio de Janeiro Olympic Games.

As officials greeted each other inside the City of the Arts auditorium, a handful of protesters gathered outside with banners that read "The Corruption Olympics", nodding to Brazil's largest-ever corruption scandal, involving five construction companies working on projects for the Games. The ceremony went ahead will full-blown optimism, however, and Bach said that each of the organising bodies was powering ahead full steam.

"I am very confident that everything will be ready and that the organising committee, the city, the federal government, the state of Rio, that they all will maintain their dynamism, because they know that there is still pressure, there is no time to lose, but on the other hand everybody knows that if this dynamism continues then we will have great Games," said Bach.

The Olympic village is 84% complete, and the swimming pool, media centre and the three arenas that will host six indoor events are all more than two-thirds ready, according to numbers released by the foreign ministry. Among the venues where most work is needed are the velodrome and the hockey pitches, which are only half completed.

Work on temporary venues for the rugby and beach volleyball is still to begin, as are final alterations to the track and field stadium and the Maracana, where the opening and closing ceremonies and the football finals will take place.

A disease-causing bacteria has been found among special forces' horses kept at the equestrian venue in Deodoro, while independent studies released last week showed dangerously high levels of viruses and bacteria in the waters where rowing, triathlon and sailing events will take place.

Bach said athletes' health was the priority for the committee and that all guidelines were being followed.

"What is important for the IOC is safe conditions for the athletes and for a fair competition, and this is why more tests will be done, and the IOC is looking forward so that the guidelines of the World Health Organisation are respected. So far, this has been the case and we can see that there are no imminent, significant risks for the athletes," said Bach.

Rio promised to reduce pollution by 80% in the bay as part of the Olympic bid to transform the city, but the municipal government has already admitted this target will not be met.

In spite of this, Bach was optimistic that the Olympic process will create a new Rio de Janeiro.

"There is a Rio de Janeiro before the Olympic Games and a better Rio de Janeiro after the Olympic Games, with all the improved infrastructure, with the redevelopment of the port area, with better public transportation, with more opportunities for tourism, that means more opportunities for jobs, so there is really a great, great legacy we can expect from these Olympic Games, like in Barcelona," Bach said.