RIO DE JANEIRO — David McLaughlin was thrilled to be in Brazil. He had arrived here from Ohio State University on a Fulbright grant to research Brazilian hip-hop music with his wife, Sarah Lowry, a scholar of Russian literature. The graduate students, newlyweds, set out one morning in June 2010 to search for an apartment in the beachfront neighborhood of Copacabana.

Then, while crossing a bustling avenue, the asphalt under their feet started to tremble. A fireball surged suddenly from a manhole, enveloping Ms. Lowry in flames. Mr. McLaughlin leapt on her and extinguished the fire. But Ms. Lowry had burns on 80 percent of her body and spent 70 days in the hospital here. Mr. McLaughlin was burned on 35 percent of his body.

“The explosion was one of the most traumatic experiences I can imagine,” Mr. McLaughlin, 34, said in a telephone interview from New York, where he and his wife now live. “Almost three years later, recovering is made more complicated every time we learn there’s been a new explosion on the streets of Rio.”

Since 2010, manhole explosions here have shattered windows, flattened cars and injured passers-by. An explosion in 2012 killed a worker at Rio’s port. While the rate of explosions has slowed, the city was rattled yet again in December after a manhole erupted behind the Copacabana Palace, the neo-Classical-style gem that is arguably Rio’s most luxurious hotel. A motorcyclist narrowly escaped the recent blast, filming with his cellphone his motorcycle going up in flames.