BEIJING — Reports that Beijing’s already notorious smog contained bacteria with antibiotic-resistant genes spread through the city last week like pathogens in a pandemic disaster movie.
“Drug-resistant bacteria make people very afraid,” The Beijing Evening News said in an article reposted by Xinhua, the state news agency, as news of a scientific study by Swedish researchers spread during yet another flare-up of hazardous smog.
That was an understatement.
The actress Zhang Ziyi perhaps best summed up the feelings among many of Beijing’s 22 million residents by writing on her Weibo account on Saturday that the smog made her want to pick up her 11-month-old daughter and fly away. Ms. Zhang worried that it “made it easier to get sick.”
By Monday, most Chinese news reports speculating about the threat had been taken offline, replaced by articles quoting an unnamed expert from the city’s Health Department advising: Nothing to worry about.
By midweek, People’s Daily, the Communist Party newspaper, had also concluded the fear was unfounded, citing an author of the study, whom it misidentified as Joseph J. Larson (in fact, Joakim Larsson), at the Center for Antibiotic Resistance Research at the University of Gothenburg in Sweden.
But to cynical Chinese, accustomed to chronic smog and other health hazards including melamine in baby milk powder, the use of recycled oil in restaurants and clenbuterol-fed pigs, the censorship and rebuttals merely signaled that there was, perhaps, something to worry about.
“Speechless!” and “Run, here comes an expert!” were two typical comments circulating online, now deleted.
“Hurry and develop a face mask that keeps out harmful bacteria and superbugs,” a user identified as Hengkong chushi wrote in response to an article on Tencent, titled: “Officials Respond to Beijing’s Antibiotic-Resistant Smog Superbugs: No Harm to Humans.”
“Don’t just say ‘no harm,’ ” another commenter named Sun Rain wrote. “Hurry up and develop new laws and new drugs, to fend off a major peril that could develop.”
So what exactly, if anything, in the study, published in October in Microbiome journal, should concern Beijing’s residents?
The answer: Perhaps not too much, if the issue is contracting a disease by breathing. Though the researchers found antibiotic-resistant genetic material in the smog, they did not find live bacteria capable of infecting anyone. The real concern is the possible link to a growing health problem, antibiotic resistance.
Antibiotics are heavily overprescribed in China, contributing significantly to the problem, doctors and researchers say.
The study said “very little if anything about risks for acquiring an infection from breathing urban air,” Mr. Larsson, professor of environmental pharmacology at the university’s Sahlgrenska Academy and director of its Center for Antibiotic Resistance Research, wrote in an email responding to a request for comment.
In the report, the researchers studied different locations around the world for antibiotic-resistant genes, including the human gut, the skin, wastewater, soil, pharmaceutically polluted sites, and, in an apparent innovation, Beijing smog.
In what they described as “a limited set of deeply sequenced air samples from a Beijing smog event,” they identified about 64 types of antibiotic-resistant genes, making Beijing smog one of two environments with “the largest relative abundance and/or diversity” of antibiotic-resistant genes, including genes with resistance to last-resort antibiotics. The other, already known, is environments polluted by pharmaceutical factories.
“We have studied DNA from bacteria in the air and found a large variety of genes that can make bacteria resistant to antibiotics, including some of the most powerful antibiotics we have,” Mr. Larsson wrote in the email. “This was a surprising finding to us, and we think it warrants further studies.”
Others appeared to agree.
“This is important work that may provide insights into the dissemination of antibiotic resistance not only in Beijing but in other cities as well,” W. Ian Lipkin, director of the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health, wrote in an email.
“It’s not clear that bacteria in smog are a health threat,” Dr. Lipkin wrote, noting that smog may be the more likely cause of health problems.
“What is clear is that the air isn’t clear. Pollution results in damage to airways that increases susceptibility to a wide range of viruses as well as bacteria,” he wrote.
“An additional take-home point is that antibiotic-resistant bacteria are ubiquitous in the environment,” Dr. Lipkin wrote.
“One question not addressed is whether smog stabilizes bacteria in a way that normal air does not,” he added. “Bacteria probably don’t replicate in the air. More likely that they settle somewhere and do, exchanging genetic material in liquid or on surfaces.”
State news outlets are dispensing health advice: To minimize illness during smog attacks, get enough sleep, eat foods that help you expectorate, flush out your nose with salt water and wash your hands.
Heavy smog is predicted again in Beijing for three days, starting on Friday.