For all the things that have gone wrong for Olympic host Brazil, one important one has gone right: The weather gods have kept temperatures low enough to help prevent the spread of the Zika virus.
The gathering of thousands of people to attend the Olympic Games had raised fears that Zika, which has infected more than 1 million people in Brazil, would be carried by the country’s mosquito swarms to visitors, who would then take it back to their home countries.
“Undoubtedly the Rio Olympics will be an amplifying event for Zika,” predicted Lawrence O. Gostin, a Georgetown University professor and global health-law expert.
But after an unusually warm summer south of the equator, winter has stuck to script and kept the nighttime temperature in Rio below 70 degrees for the past several weeks, a trend forecast to continue into next week.
That has seriously hampered the female Aedes aegypti mosquito’s ability to spread the virus: The temperatures remain low enough that most of them don’t live long enough to pass it on during their daytime feedings (the males do not bite humans).
A June report from the Oswaldo Cruz Institute, a research center funded by Brazil’s Health Ministry, said that as long as the daily low temperatures remained below a range of 72 to 78 degrees, the incubation period for Zika should be longer than the lifespan of Aedes aegypti.
The fear of a Zika contagion also has been dampened by an intense mosquito-eradication program that for the past two months has sent inspectors daily in and around Olympic venues and the village to ensure that they are “watched and constantly clean,” according to the country’s Sports Ministry. That seems to be happening in the venues that McClatchy reporters have visited.
Workers are looking for anything that can hold water, even bottle caps, which can provide a breeding site for mosquitoes.
“They are doing the things to ensure that in Rio de Janeiro it’s been controlled,” said Marco Vale, a sanitary supervisor at the Sambodromo venue, the long stadium that usually hosts Carnival parades but has been converted for use in Olympic archery contests.
Vale walked the grounds with McClatchy on Saturday, radioing orders to workers to ensure that trash bins are emptied and water bottles collected.
Sitting in the stands, Robin Garrett of Wellington, Missouri, was watching her son Zach help win silver for the U.S. archery team. Zika was “the last thing on my mind,” she said. Her son is grown and she wasn’t worried about getting pregnant, so her only Zika precaution was long pants. Zika in pregnant women has been linked to microcephaly, a devastating birth defect that is characterized by a smaller-than-normal head and an underdeveloped brain.
The same zeal was not evident just across the street from the venue, however, in the Nova Cidade neighborhood near the Praca Onze subway, which brings visitors to the Olympic venue. Conditions in Nova Cidade show the difficulty of the government’s task. Residents like Anelise Santos, drinking beer in front of a humble home, laugh off Zika concerns.
“There isn’t anything here,” she said between gulps, sitting on a chair in front of a puddle – the kind of standing water mosquito larvae thrive in.
A few doors down, a shirtless Adilson Marian da Silva walked by trash.
“Thank God it’s not here,” he said.
That’s not very likely. Brazil’s slums, with their lack of sanitation and window screens and their dense populations, are considered major reasons Zika has spread so widely. In a survey of the virus’s spread, Brazilian health officials estimated early this year that there are 157 cases of Zika infection for every 100,000 inhabitants in Rio, a city of 6 million. Four of every 5 residents who contract the virus won’t show any symptoms of being ill.
With the proximity of slums to the Olympic venues, the risks are high for everything from Zika transmission to crime to stray bullets like the one that ripped through a media tent at the Deodoro venue Saturday during equestrian events.
Alex Sandro, who lives in the poor Campo Grande area of Rio, not far from the Olympic village, said, however, that since June government officials and firefighters had been frequent visitors searching for mosquito-breeding water. Even drones were used in the area, he said, to seek out any hidden sources of mosquito breeding.
“Everybody had to fall in line,” he said, noting that mosquitoes seem largely gone from his neighborhood.
Still, Zika remains a concern. Bug-spray maker Off was selected as a corporate sponsor of the 2016 games. Hundreds of journalists covering the games received courtesy cans when registering at the Olympic press center, and the bug spray is selling briskly at official Olympic stores.
The winter decline in mosquito populations in Rio also may not hinder the spread of Zika to the United States. Air travel has been the source of most Zika infections detected in the United States – but few of those are likely to come from Olympic travelers. The Atlanta-based Centers for Disease Control and Prevention has noted that travel to the Olympic Games represents only 0.25 percent of the annual aviation travel to areas with Zika transmission.