There are plenty of times when you might wonder: How far does a cough or a sneeze travel? During a global pandemic involving a respiratory illness is certainly one of them. Prior to the new coronavirus pretty much upending life as we know it, you might have simply given someone the side-eye if they coughed near you in the grocery store or on public transportation. And look, coughing in public without covering your mouth has always been a public health nuisance with the potential to cause harm. But now it can be a matter of life and death to a huge number of people — to the point that doing so intentionally might result in a police warning or arrest.
And it makes sense to worry about other people coughing and sneezing in your general vicinity these days. COVID-19 spreads easily—and a big part of that spread is through respiratory droplets, like from a cough or a sneeze. What that means is that if someone coughs, sneezes, or even talks, small droplets can expel from their mouth. You can get sick if those droplets land in your mouth or nose and then you inhale them into your lungs, according to the CDC. The CDC recommends that you stay at least six feet away from people when you’re out in public, to minimize your risk of this type of transmission. But is six feet actually sufficient? If someone is coughing or sneezing, is it possible that they’re expelling those droplets farther than just six feet?
Which brings us back to the original question: How far does a cough or a sneeze travel?
Here, doctors explain what you should know about how far germs spread in general when people sneeze and cough, how to keep yourself as healthy as possible, and how to protect others when you’re the sick one (whether you have COVID-19 or otherwise).
Infectious diseases have a few modes of transmission.
One of these is large-droplet transmission, Alexander L. Greninger M.D., assistant director of the University of Washington Medicine Clinical Virology Laboratory, tells us. This refers to the droplets sick people expel when they cough, sneeze, or talk. If someone else inhales those secretions, they can get sick too. Illnesses like the flu, the common cold, and pertussis (whooping cough) are thought to mainly spread this way. Same goes for COVID-19.
Then there are infections that fall into the airborne-transmission category, like measles, tuberculosis, and chickenpox. Unlike large droplets, which need to quickly come into contact with someone’s mucous membranes in order to cause an infection, airborne transmission allows potential pathogens to remain suspended in the air for some time after someone coughs, sneezes, or talks. (Remember, not all germs are actual pathogens that can make you ill.) Then someone else can breathe in those particles and get sick.
Some illnesses can infect people via both forms of transmission. For instance, the flu mainly spreads through large droplets, but the CDC notes that it can be airborne as well. And there’s some preliminary research that suggests that COVID-19 has the potential to hang out in the air for a few hours as well, although more research is needed.
There’s also the potential to get sick through touching something that has the virus on it and then touching your mouth, nose, or eyes with that virus now on your fingers. That’s one way that people suspect COVID-19 is transmitted—the study mentioned above found evidence that the virus lasts for up to four hours on copper surfaces, 24 hours on cardboard, and two to three days on plastic and stainless steel. If someone sneezes or coughs and those droplets get on something you then touch (or if they have the virus on their hands from touching their face or blowing their nose and then touch something that you then touch), that could be a potential way to contract the disease.
Infectious diseases can also of course spread in other ways, such as through direct contact (like if you kiss someone who’s sick). But since we’re talking about how far germs spread through the air, we’re going to focus on large-droplet and airborne transmission.
So, how far does a cough or a sneeze travel?
The important thing to understand here is that scientists really only have estimates for how far coughing and sneezing can spread germs, not hard numbers. Some of this might even depend on how forcefully a person coughs or sneezes. (Scream sneezers, we’re looking at you. But we also know it’s not your fault.)
Large respiratory droplets containing pathogens like influenza can travel up to six feet when a sick person coughs or sneezes, according to the CDC. A 2014 study by MIT scientists published in the Journal of Fluid Mechanics suggests this number may be way higher for smaller airborne particles. Researchers used high-speed video upwards of 1,000 frames per second to record sprays of mist as well as human coughs and sneezes, finding that smaller droplet particles traveled as far as 2.5 meters horizontally through the air. That’s more than eight feet.
The study also recorded smaller airborne droplets spraying 13 to 20 feet vertically in the air, which researchers noted was theoretically high enough to enter and travel through some ceiling ventilation systems in some buildings. The researchers posit that this impressive (and kind of nauseating) distance is because smaller pathogens can travel as part of a buoyant cloud that extends their reach.
The problem with airborne pathogens isn’t just how far they can spread, it’s also how long they can hang out in the air and on objects. A lot of this depends on the pathogen in question. Measles, for instance, can live for up to two hours in the air and on surfaces, according to the CDC. This illness is so contagious that 90% of people who are close to a person with measles but who aren’t immune (like through vaccinations) will catch the illness. That’s especially scary considering the recent measles resurgence happening in some parts of the United States.
For COVID-19, the study mentioned above found that coronavirus particles were detected in the air for a median of about 2.7 hours. That said, more research is needed.
What happens if someone sneezes or coughs on or near you?
It’s normal to feel completely grossed out by how far germs may be able to travel—and right now to feel really scared by it.
Yes, someone who is ill sneezing or coughing on or near you can boost your chances of getting sick. This is true even if you hold your breath. “The particles will stay there for many minutes, and in some cases many hours, and you can’t hold your breath that long,” Keith Roach M.D., associate professor in clinical medicine at New York Presbyterian Hospital. Or you could rush away from the scene, but the particles may still be on your clothes, which you might touch later. You get the picture.
The reason that COVID-19 is so contagious is because it has never existed before, which means that no one has immunity to it. But with diseases that have been around for a while, like colds and flus, the good news is that even if someone sick sneezes or coughs around you, factors like your past exposure to viruses and your vaccination record could end up protecting you from that illness, depending on the strain in question. (Make sure you’re up to date on your flu vaccine every single year. Is it 100% effective? No. Does it still slash the death toll and number of hospital visits linked with the flu each year? Yes.)
If you have good hygiene habits, that’s another point in your corner.
What else can you do to avoid getting sick?
Good hygiene is essential. Wash your hands, people! Soap and water are most effective at preventing transmission of illnesses like COVID-19, the cold, and the flu, but Dr. Roach recommends keeping alcohol-based hand sanitizer at the ready for the times you can’t wash your hands. Your sanitizer should be at least 60% alcohol in order to be as effective as possible. Even with great hand hygiene, you should also try very hard to avoid touching areas like your mouth, nose, and eyes, since those are possible portals for pathogens. That’s always true, but especially important right now.
And if someone in your household is obviously sick or has what you suspect might be COVID-19, make sure that they’re isolating in a separate room in the house if at all possible, and that you’re sanitizing high-touch surfaces (like doorknobs, light switches, bannisters, and so on) on a regular basis. Here’s more information about how to keep your house clean in case of the coronavirus, as well as how to care for someone with a suspected case of COVID-19.
Finally, Dr. Greninger recommends prioritising lifestyle measures that can help your immune system work as well as possible, like getting adequate sleep. Eating in a way that fuels you and trying to manage stress are good ideas too (when possible, since we know it’s not always—especially right now).
How can you protect others from your own coughs and sneezes?
If you’re sick (with anything, COVID-19 or otherwise), cover your face when you sneeze and cough. This can definitely be helpful in sparing others from your illness, Dr. Greninger says. Just don’t cover your face with your hands, because that makes it all too easy to spread those germs around. Instead, the CDC recommends coughing or sneezing into a tissue and then throwing it away, or sneezing into your upper shirtsleeve or elbow, completely covering your nose and mouth.
Unfortunately, even the best cough and sneeze etiquette can’t fully stop the spread of disease, Dr. Roach explains. A small 2013 study of 31 people published in BMC Public Health found that some droplets—especially smaller ones—still spread when the participants were practicing good cough etiquette, including coughing into their shirtsleeve or elbow.
As the scientists explained, this is because some particles manage to find the path of least resistance around whatever is blocking them. But pure physics dictates that putting an obstacle in the way of any pathogens is preferable to just spewing them into the air without any barriers. Even though covering your nose and mouth isn’t foolproof, it’s definitely better than nothing—which is precisely why the CDC recommends it.
In addition to following proper sneeze and cough etiquette, you should wash your hands thoroughly and frequently when you’re sick. (Especially if you slip up and cough or sneeze into your hands.) It’s also important to keep your distance from people when you’re ill and to frequently disinfect surfaces you’re always touching. Find out what else you should do if you think you have COVID-19 here.
In situations involving compromised immunity, face-blocking devices may help.
If you’re sick and spending time with people who have compromised immune systems, or if you have a compromised immune system yourself, you may want to step your illness prevention up a notch. Depending on your specific scenario, it could make sense for you or the people around you to wear a device like a face mask or N95 respirator. Although, heads up that these are in extremely limited supply right now, and that health care professionals across the country are in desperate need of them to keep themselves safe while they take care of us. So if you don’t absolutely need an N95 respirator mask, absolutely go for something else.
Face masks can block many large droplets, while N95 respirators are designed to obstruct the passage of those very small airborne particles that can lead to illness, according to the Food and Drug Administration (FDA). But a 2011 systematic review published in Influenza and Other Respiratory Viruses, which looked at 17 different studies, suggests that these devices are much more likely to help prevent illness if worn consistently and correctly. If you’re curious about these illness-preventing measures, talk to your doctor for advice and guidance on proper usage. And even if you do opt to use these, you should still practice the above measures to make sure you—and those around you—can remain as infection-free as possible.
This article was originally published on SELF