Following a video that proclaimed Rio “a tropical paradise,” U.S. Olympic Committee executives took the stage at the Beverly Hilton earlier this week to the irrepressibly upbeat song by Pharrell Williams, “Happy.”

But the carefully established tone of the USOC media summit, designed to introduce nearly 700 journalists to 110 of the athletes expected to represent the United States at the 2016 Rio Games, proved short-lived.

Instead of queries about projected medal counts, USOC executives were peppered with questions about the Zika virus; raw sewage in the water of Guanabara Bay, host of sailing events; and Brazil’s economic collapse, which has spurred concern that promised subway lines won’t materialize, tickets will go unsold and some venues won’t be finished in time for the Aug. 5 Opening Ceremonies.

Many of the athletes in attendance, eager to talk about their preparations for the Games, were asked about the troubling issues of pollution, water-borne disease and mosquito-transmitted virus, as well. Sailors, rowers and any athlete whose field of play includes open water were polled in detail.

Most navigated the terrain deftly, careful not to insult their Olympic hosts or fuel story lines that distracted from their goal: to compete to the best of their ability, regardless of circumstance.

Triathlete Greg Billington said he felt the issue of water quality in Rio had been overblown by the media.

“Everywhere you go — you travel out of the country, you’re always doing everything you can to stay healthy,” said Billington, 26 , of Spokane, Wash. “This place is no different. They’re not going to dump a bunch of chlorine in there so that we’re swimming in our backyard pool.

“The thing I’m most afraid of probably from the water is jumping in with 55 guys who are amped to crush the swim and then having to all come together in one tiny line and hoping I can get out of the water with all my teeth intact.”

Said rower Gevvie Stone, a Princeton graduate who’s preparing for her second Olympic Games: “I train in the Charles River, which is not known to be the cleanest in the country. It is technically swimmable right now, but we had an algae bloom two summers ago. Anywhere in rowing you can come across [polluted water] as an issue — even in Boston.”

But when it comes to Rio’s sailing venue, Guanabara Bay, Olympic sailors are being advised to take more stringent precautions. That’s because the bay has traditionally been a repository for raw sewage, and Brazilian officials are lagging behind in their vow to stop the practice and clean it up.

“They’ve taken a lot of steps to mitigate the pollution in the bay,” noted Alan Ashley, the USOC’s chief of sport performance. “While it’s not yet clean, I think that’s something they’re striving toward.”

Mario Andrada, communications director for the Rio Games, provided journalists with raw data that testified to the progress to date this week, but the issue remains unsettling, nonetheless.

In pursuing hosting rights for the 2016 Summer Games seven years ago, Brazilian officials pledged to treat 80 percent of the raw sewage being dumped into the bay, Andrada said this week. At that point, he noted, only 12 percent of the sewage was being treated.

“Now we are over 60.2 percent being treated,” Andrada added. “We’ll get close to 65 percent [by the start of the Games].”

According to an Associated Press report based on independent tests of Guanabara Bay, its water includes disease-causing viruses linked to sewage at more than 1,000 times above what is deemed alarming. Ingesting even a small amount can cause serious illness.

In response, Rio organizers have posted a suggested protocol for sailors to follow on its website.

“Granted, it’s all in Portuguese,” noted Ashley, the USOC sport performance chief. But USOC officials are sharing its suggestions, along with advice issued by the Centers for Disease Control and World Health Organization, with their athletes.

The protocol for sailors includes tips on keeping boats and paddles clean, carrying drinking water in boats and other, largely common-sense ways of avoiding contamination.

Wisconsin native Annie Haeger has sailed in Guanabara Bay eight times in preparation for the Games, trying to get acclimated to its swirling currents, and had no ill effects. If water splashes in her mouth, she said, she immediately will swill some cola and spit it out. She’s also fastidious about cleaning the boat, her clothing and herself after each outing. And she and her teammate have mastered the art for dealing with any debris that hits their boat.

“No matter what it’s like down there, we’re going to go down and sail our best and hopefully come away with a gold medal,” Haeger said.

Meanwhile, cleanup efforts continue.

According to Andrada, fences have been erected at the mouth of tributaries to Guanabara Bay to corral garbage and debris, which is then being carted off in dump trucks. Officials are testing the water for bacteria every second week. During the Games, the bay’s water will be tested daily.

“I can 100 percent assure everybody it’s going to be a fair competition, with no risk for health of the athletes,” Andrada said.