There are now tens of thousands of confirmed cases of the coronavirus disease in the United States. The Centers for the Disease Control and other health experts have asked people to avoid large groups, stay at least six feet away from one other, and self-quarantine when sick. KNAU’s Melissa Sevigny spoke with infectious disease expert Paul Keim about why these measures matter. He’s a professor at Northern Arizona University and the nonprofit research institute TGen.
Melissa Sevigny: So tell me a little bit about how this virus behaves and really how infectious it is.
Paul Keim: I actually think of the world as a series of probabilities. When you’re six feet away from somebody else who has this disease and they cough, a lot of those particles are going to go flying out of their mouth and then they’re going to fall to the ground, or fall to the surface around them, and the hope is, by being six feet away you’ve lowered your probability of encountering one of those to a very small number. We don’t know what that number is. Six feet is just a guideline. But the further you are away from somebody, the better. Now, one thing that isn’t fully appreciated is there’s another component to this probability of getting infected, and that’s time. I was in a grocery store in Flagstaff and I had to go up the cashier and pay for the food, and I was only about two feet away from her. But I tried to make sure I was only two feet away from her for about a minute. And then I got further away.
Will wearing a mask help at all with that?
We really don’t recommend that people wear masks if they’re healthy. Among one of the consequences of doing that is the masks aren’t available for healthcare workers and folks who really need them… You know, the single most important thing that people can do right now is what we call self-quarantine. If you end up with flu like symptoms you should self-quarantine. You should stay at home, you should try to protect your roommates or family by creating separation in your home. What’s crazy about all this, we should have been doing this last year and year before. This is just good behavior when you’re sick.
I’ve seen research that shows that the virus will linger on surfaces for something like 72 hours, and this is new research, it may change. But it is possible, I guess, to pick it up from a shopping cart handle or something like that?
Yeah, absolutely, it is possible. You want to have good control of your hands, keep them away from your face…. and you’ve heard it a thousand times from other people, wash your hands. The best way to wash your hands is with soap and water. And if you can’t do it frequently, these alcohol based disinfectants, sanitizers, are good, too. Not as good as washing your hands, but they work.
Can you talk a little bit more about the risk of getting the virus, and also it being serious if you do get it?
We know that there are special at-risk populations involved with this. People who have other diseases, what we call co-morbidities, are of particular importance here: people who have diabetes, high blood pressure, compromised immune systems, people are undergoing chemotherapy for cancer… If you smoke you’re at higher risk, if you have any type of lung disease you’re at higher risk. And age is very important... What your risk is if you’re younger, it’s not zero. Younger people are not having the same frequency of severe disease, but there are people who are younger who are have severe disease… And so these preventive measures actually have to be put into place before it seems like you need them. That’s why in Arizona we’re already practicing social distancing, the universities are closed, the restaurants are closed. All that’s important to do before you have a big intense outbreak.
From a broader perspective, there’s a risk that everyone will get sick all at once and really overwhelm our hospitals.
You’ve heard this expression “flatten the curve.” That’s real important that we don’t end up with a tsunami. The analogy I like to use is, if you’re on the beach and the tide is rising you’ve got time to pick up the toys and lawn chair and move them up the beach. But if a tsunami comes in everything’s just gone. It just happens all at once. We don’t want that crashing wave on our population, because it will overwhelm everything from our health care to our transportation to our economy. If we can flatten the curve, even if we end up with the same number of cases, we can deal with it.
If I have the flu I’m likely to give it to one, maybe two more people, but COVID-19 is more infectious than that, isn’t it?
So the number you’re referring to is called R naught. Epidemiologists like this number, it describes what the average number of people who will get infected from another person would be. The numbers for flu are somewhere between about 1.3 to 1.5. For COVID-19 virus the numbers that have been published are more like 2.6 to 3.4. That’s a big difference actually. When you do the modeling, that single extra person who gets infected on average, it really spreads the disease a lot further…. But it also comes over to if you go to a soccer match in northern Italy and you’re hugging and kissing everybody because your team just won, your R naught could go really high. That exact scenario may have played out in the Italian outbreak… The situation makes a difference on that number and then the severity of the disease. So when wte’re talking about these R naught values and how infectious the virus is, it’s important to know there’s a context for that, and that we can affect that.
Okay, so how we behave really does make a difference.
It’s critical. Lots of things in life we can’t control, but this is an example of where if people will modify their behavior, they can make a difference…. So practice social distance, wash your hands, self-quarantine, very very important. I think in a neighborly way you can remind others to do this as well… And we will come out of this.
Paul Keim, thank you so much for joining me today.
You bet, Melissa.