The Olympic athletes converging in Rio de Janeiro in coming days have expressed anxiety about sailing and rowing in waters contaminated with viruses, trash, and superbugs. But at least the athletes get to head home after they compete.

For many Brazilians, filthy waterways are an inescapable fact of daily life. And it's making them sick.

Across Brazil, untreated sewage flows through poor and working-class communities, causing vomiting, diarrhea, and skin disease. Hepatitis A, contracted from the polluted waters, is endemic.

In Manguinhos, one of Rio's dense urban settlements known as favelas, kids swim and play in a sewage-filled river that runs past their homes. On a recent visit, the water reeked of human waste. When it rains, the dirty water overflows and floods the neighborhood. It has even poisoned a community garden that was supposed to provide healthy food, said Geandro Pinheiro, a sanitation expert and public health advocate who works nearby.

In Rocinha, a favela crammed on a steep, rugged hill, community activist José Martins de Oliveira has counted 23 sewage waterfalls, each of them flowing down toward a beach popular with surfers. That's 23 sewage waterfalls just in this one community, home to about 160,000 residents by locals' count (and about half that according to official estimates).

Waterfalls of raw sewage

On a recent afternoon, Oliveira, who's 69, climbed silently through a labyrinth of alleyways and big cement steps. Deep in the favela, he stopped. He gestured to the right, where pipes carrying gray water and sewage poured out of houses, splashing down to form an open stream.

Then he walked on to another waterfall, and another. All smelled nasty. They were so close to pedestrian walkways that Oliveira had to keep stepping aside to let people pass.

Fernando Spilki, a leading Brazilian virologist, called the sewage waterfalls "very sad" — and not unique to Rocinha: They can be found in poor communities across the nation.

Exposure to raw sewage causes gastroenteritis, especially in people who are young, old, or have compromised immune systems, he said. While some adults recover quickly, children can die from dehydration. The illness is a major cause of hospitalization in Rio, and it can have long-term effects: Kids who get repeated cases of gastroenteritis can develop learning deficits.

Spilki worked with The Associated Press last year on an investigation that discovered dangerous viruses, often found in human waste, lurking in Olympic water venues. Treating sewage, he said, will be Brazil's "greatest challenge" in the decades ahead.

Renata Picão, a microbiologist at the Federal University of Rio de Janeiro who recently found drug-resistant bacteria in the water on five famous Rio beaches, suspects that hospital waste is partly to blame. The bacteria, dubbed superbugs, have proven deadly in a hospital environment, but it's not clear yet if anyone has gotten sick from swimming with them.

Feeling invisible

Rio officials say they're treating more of the city's sewage — about 50 percent, up from 11 percent — before it's dumped into the waterways. But a recent wave of public improvements in the Rocinha favela failed to address the open sewage, state officials acknowledge. Brazil's federal bank is now considering a plan that would enclose the open sewage in pipes, but the bank has not yet approved the project, according to the state public works department.

Many residents here feel they're invisible to the government. As evidence, they point to the new Metro line chugging along to Olympic Park. It will stop right at Rocinha, but you wouldn't know that: The stop is called "São Conrado" — with no mention of the enormous favela it serves.

Oliveira and others are fighting to change the name: "We want to be seen and treated as citizens," he said.

As for the Olympic venues, well, Rio's Olympic committee famously promised that Guanabara Bay, which will host the sailing competition, would be "80 percent clean" in time for the Games.

The effort has come nowhere close — a fact that Alex Sandro dos Santos, head of a local fishermen's association, called the biggest "broken promise" of the Olympics.

Andre Correa, environmental secretary for the State of Rio de Janeiro, has conceded that the claim the bay would be 80 percent clean for the Games was "misplaced." He said the job will take 25 years and cost $6 billion, which the government doesn't have.

As a stopgap measure, Rio's Olympic committee has deployed 12 "eco-boats" to haul tons of trash out of the water where sailing races will take place. Seventeen barriers hold back additional trash from entering the bay.

'There is no future'

But further upstream, the eco-boats don't run. Sewage, trash, leaking oil from petrochemical plants, and sediment have invaded the bay.

In Tubiacanga, a small community near the international airport, trash has piled up on the shore for years. On a recent visit, a 5-year-old boy climbed over plastic bottles and Styrofoam as he flew a kite. Two girls caught tiny crabs along the shore.

Sergio Ferreira, 65, who has been fishing in the bay for most of his life, said fishermen often get sick, and sometimes die, from the water. Those who wade in the polluted mud in the mangroves to catch crabs get skin diseases and stomach bugs. Decomposing trash from an abandoned trash dump across the bay swirls around in the water and washes ashore, he said.

"I feel devastated," he said. "There is no future" for fishermen.

"Guanabara Bay is asking for help," he said, looking wistfully out the window at the water. "Nature is asking for help."

This story was produced by STAT, a national publication covering health, medicine, and life science. Read more and sign up for their free morning newsletter at You can also follow STAT on Twitter and like them on Facebook.