Amid concerns about health, doping and security, Rio de Janeiro is about to host Summer Olympics. Ceremonies and 300 medal competitions in 41 categories run from Aug. 5-21 in the South American seaside city. Action will be broadcast daily on NBC and streamed live at NBCOlympics.com, showing sports such as archery, badminton, beach volleyball, boxing, canoeing, cycling, gymnastics, rowing, rugby, table tennis and water polo. U.S. medal contenders to watch include swimmers Michael Phelps and Katie Ledecky, 19.

Athletes, fans and journalists from around the world will see a modernized and cleaned-up Rio. Brazil spent tens of millions of dollars on urban renewal and transport improvements, including new tram lines, plazas and athletic stadiums. Still, there are worrisome issues. One of the biggest involves a Zika virus outbreak that has spread from Brazil, including to the United States. In late May, 150 public health experts and scientists said the Olympics should be delayed or moved to avoid possibly speeding up the mosquito-carried virus' global spread. Some athletes from the U.S. and elsewhere withdrew from consideration to avoid a possible risk to their pregnant wives if they came back infected. Rio has about 26,000 suspected Zika cases, the most of any Brazilian state.

A different health concern faces members of sailing and rowing teams. Severe water pollution exists where they'll compete. Early last month, raw sewage and trash still flowed directly into the water from poor hillside neighborhoods, prompting intensive cleanup efforts. Another issue is athletes' use of banned performance-boosting drugs. Russian weightlifters and track athletes are disqualified from competig in Rio for that reason. Separately, several countries complain that Olympic Village dorms are in bad shape, mainly because of plumbing and electrical problems. Australia sent more than 700 athletes to stay in hotels during repairs.

American gymnast says: "It's the Olympics! . . . I’m going. This is my shot, this is big. I don’t care about no stupid bugs!" – Gabby Douglas, 20-year-old defending champion

U.S. swim coach says: "She [Katie Ledecky] has an intensity to her swimming that I have never seen in a distance athlete. She’s completely fearless." – Bob Bowman

Jamaican track star: Usain Bolt hopes to make history as the first sprinter to win gold in three consecutive Olympics.