"All of those go into what I would think of as a combined likelihood or combined probability" of getting infected, Barocas says.Ĭonversely, not every type of lengthy interaction is equally risky, he says. For example, was the infected person coughing? Was the person wearing a mask, which can help contain a lot of the infectious particles someone might be breathing out? Were you indoors or outdoors, where airflow would quickly disperse any infectious particles the person might have exhaled? How infectious was the person at the time of interaction? (Studies have shown that people with the coronavirus are most infectious just before and in the first few days after they start to show symptoms.) If an infected person were to cough on you while walking past, that would constitute a high-risk interaction – even if it was brief, he says. How you interacted also matters a great deal, Barocas says. "Certainly, if you're in very close contact with somebody who's shedding a lot of virus, and you happen to get a droplet on your hand and then wipe your nose, that could take far less than 15 minutes" to infect you, says Angela Rasmussen, a virologist at Columbia University Mailman School of Public Health. "We don't have strong evidence for exactly what the right distance or the right duration is, or else we'd use that," Gurley says.Īnd lots of variables can affect the risk of infection from close interactions, experts say. She says the 15-minute guideline is a way to help contact tracers quantify which types of interactions were long enough to be meaningful in this context.īut again, it's just a guideline, not a hard and fast rule. Instead, she says, infections were occurring when people had "meaningful" amounts of close contact – such as traveling, dining or living together – that had a higher probability of resulting in transmission. "Even when they found lots and lots of very casual, quick contacts, that's not where they saw evidence of transmission," she says. So where did that 15-minute part of the guideline come from? Gurley says it's based on earlier data from China on who was being infected and how infections occurred. Gurley says in some jurisdictions, contact tracers also look for so-called proximate contacts – people who were in an enclosed room with an infected person at greater than 6 feet away – though they aren't considered close contacts under CDC guidance. If you're in a crowded room with lots of unmasked people talking, "whether you're 15 minutes or within 6 feet, it may not actually be that important anymore because there's so much virus in the air," Barocas says. In a poorly ventilated, enclosed space, these smaller particles can build up in the air over time. That's where the 6-foot guideline comes from – though it's just a guideline, not a shield of impenetrability.Ī person can also expel smaller infectious particles that linger in the air for minutes or even hours and travel farther than 6 feet in a room, Barocas notes. Some of these particles are released as droplets, which generally fall to the ground within a few feet of the person who exhaled them. The coronavirus spreads when an infected person releases infectious particles while talking, coughing, singing, sneezing or even just breathing.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |