RIO DE JANEIRO • When a young woman joined her family for a barbecue one recent Sunday in southern Brazil, soon after a night on the town, she had no idea she would infect 18 relatives with the coronavirus, and three of them would eventually die.
Young Brazilians, energised by the arrival of summer and suffering from social distancing fatigue after months of restrictions, have taken to the streets and beaches to party in increasing numbers.
Public health experts warn that an accelerated transmission rate among young people has been a major contributor to a surge in coronavirus cases and deaths that they fear may be a second wave hitting Latin America's largest nation.
Confirmed cases in the past week have risen to a three-month high in Brazil and deaths have jumped over the last month.
With over 6.5 million infections and more than 175,000 deaths, Brazil has the third-biggest outbreak, after the United States and India, and the second-highest death toll, after the US.
Although young people are less likely to die from the disease, they often bring the virus home to family members whose age or prior medical conditions put them at risk, filling up intensive care beds in many cities' hospitals.
Curitiba Health Secretary Marcia Huculak revealed the case of the young woman as she made an appeal to people to avoid gatherings, even within families.
State health officials declined to provide the woman's name or other identifying information, citing privacy concerns.
"We are seeing very sad cases like this one of the woman who went to a party and then on Sunday attended her family's BBQ," she said.
Young adults have felt the greatest mental impact from prolonged social isolation, with 54 per cent saying they are depressed and 70 per cent anxious or often nervous, according to research.
Easing restrictions in Brazilian cities has led to crowded bars and restaurants.
With the approaching holiday season, experts worry that Covid-19 will spread even faster.
Several cities that were dismantling field hospitals used to receive Covid-19 patients in the first stage of the pandemic are now scrambling for more hospital capacity.
As cities and states ease restrictions, however, transmission has picked up, with the last week averaging 34,700 cases and 520 deaths a day.
Rio de Janeiro has postponed until June its famous carnival party, but that has not stopped preparations for New Year's Eve celebrations that draw large crowds every year. Tickets are on sale for parties atop the city's iconic Sugarloaf Mountain.