Tanya Lewis: Hi, this is Your Health, Quickly, a Scientific American podcast series.

Josh Fischman: We bring you the latest vital health news: discoveries that affect your body and your mind.  

Lewis: And we break down the medical research to help you stay healthy. 

I’m Tanya Lewis.

Fischman: I’m Josh Fischman.

Lewis: We’re Scientific American’s senior health editors. 

On today’s show, we’re doing a refresher course on COVID. Fall and winter usually see a peak in virus cases, so we thought it would be a good time to talk about where we’re at. That means knowing where COVID is spreading, how to stay safe and when you should test yourself.

[CLIP: Show theme music]

Fischman: I really haven’t been worrying much about COVID for months now. It was summer, it was warm and nice outside, and the public health emergency ended last spring. Cases seemed low, so I wasn't thinking about the disease all that much. 

Lewis: Yeah, me neither. I've had a nice little break from COVID for a few months now, really. But the virus is still there, and it's continuing to spread, so I'm starting to get my mask out again.

Fischman: But a friend of mine just caught COVID for the third time. Another friend has been sick with it for three weeks. And it’s getting to be fall and winter, seasons when the virus has peaked in the past.

Lewis: Yeah, COVID isn’t quite a seasonal virus yet, but it does seem to follow some seasonal patterns. It spreads easily when people are indoors, like we are much of the winter. And then you add in holidays and kids going back to school, and it’s the perfect viral storm.

Fischman: These friends of mine, the ones who got sick, have been texting back and forth, arguing over the best time to use home COVID tests, and a bunch of other stuff that I think we all had a better handle on last year. I think we’ve kind of forgotten some of the basics.

So to catch up, we thought we’d talk to someone who’s been tracking the virus and public health for the whole pandemic: Katelyn Jetelina.

Jetelina: I’m an epidemiologist and publisher of Your Local Epidemiologist. I do a lot of contracting work with the CDC, also adjunct at University of Texas Health Science Center.

Lewis: Your Local Epidemiologist is a newsletter that’s become a go-to source for hundreds of thousands of people because Katelyn explains COVID research in plain English and turns it into advice for readers trying to figure out how to stay as safe as they can.

Fischman: One of the first things I wanted to know was: How do I know if COVID cases are rising in my community, so I can take extra care?

And, here’s what Katelyn said:

Jetelina: Yeah, this is really challenging to do, especially on a local level. I, [in] particular, know a lot of other epidemiologists are focused on wastewater. 

Lewis: Wastewater is sewer water, essentially. If people are infected with the virus and use the bathroom, that virus gets flushed down the drain. Then scientists can test for it. If levels go up week after week, it means the virus is spreading in the community.

Jetelina: For example, in San Diego, we have a fantastic wastewater system for viral surveillance. But really you just need like a regional kind of trend because wastewater is good for looking at trends. 

And so if that trend in your region is increasing, then, like you said, you're gonna start hearing more and more people getting infected. 

The wastewater dashboard I use is Biobot. It's super, it's pretty, it's straightforward. 

Fischman: Biobot is a company that works with public health agencies to monitor viruses in the water. And they do have a pretty nice trend dashboard on their website, which you can Google. 

Be warned, though. It doesn’t get super local. For instance, I’m pulling it up here on my phone. I live in Maryland, so I’m looking there for the county I live in—and it’s not listed. It’s just not there.

What about you, Tanya? 

Lewis: Let me take a look and see if they have one for Brooklyn—or King’s County, where I live. Um, but, I do not see anything. And I don’t see anything for New York City, so the closest one is Nassau County in Long Island. 

Fischman: So wastewater isn’t perfect. There are gaps in Biobot’s coverage, but there are other programs that might fill in. And wastewater is better than some other indicators.

Lewis: Yeah, like the number of people testing positive for the virus, or case rates. Katelyn doesn’t think those numbers are very reliable anymore.

Jetelina: So as we left the pandemic emergency, as fatigue has certainly crawled in, people are stopping to test. So certainly case data is not anything I would pay attention to. 

Fischman: She did mention something new, which I hadn’t heard about, which is a way to look at COVID and the flu together.

Jetelina: We're going into the fall, winter season—and there's going to be a lot of crap out there. And so one thing I know the CDC is updating, which should be in the next week or two, is a respiratory map by state. 

Lewis: The CDC has long had a tracker for flu-like illnesses, but during the pandemic they had a separate tracker for COVID. And now that’s changing.

Jetelina: That COVID number is going to be folded into this respiratory outlook. And I'll probably be using that to really determine when to wear a mask, for example, because I don't want flu or RSV or COVID or norovirus or whatever is out there.

Fischman: Another thing I wanted to know about was what to do if you think you’ve been exposed. I know Katelyn said a lot of people don’t do rapid home antigen tests anymore. But plenty still do. 

So you get a call from a friend who you just had lunch with. And she says she just tested positive. Should you test yourself?

Lewis: The tests are most accurate at detecting infection once the virus has had a few days to replicate in your body. The advice from the FDA and the CDC is to wait five days after exposure and then test. 

Fischman: But Katelyn pointed out there are lots of times you don’t know the exact time or day of exposure. And also that with new variants, viral loads seem to build more slowly, so it may be more useful to wait until you actually start seeing symptoms, like a runny nose, cough, a fever, the usual stuff. And then wait out a few days of those before testing.

Lewis: So—you shouldn’t take a home antigen test during the first two days you feel sick?

Jetelina: Yeah, third day, it may start increasing your viral load. But yeah, those first two days—there's a high likelihood of a false negative on your antigen test.

Lewis: Good to know. 

So, when COVID is on the rise, what’s the best way to keep yourself safe?

Jetelina: Wear a mask. Like, I have two toddlers I need to take care of. I'm traveling all the time for work. Like I just don't have time to get sick and so I wear a mask. Wearing a mask helps protect you, it helps protect those around you. Taking an antigen test a couple of days after symptoms, getting a vaccine. I mean, just go get your vaccines by Halloween. You may get infected, but you're not going to end up at the hospital.

Lewis: So that’s the advice from your local epidemiologist. We’re not in the same place we were in previous years, but COVID is still a risk. We have the tools to protect ourselves. Let’s use them.

[CLIP: Show music]

Fischman: If you want more info on how science tracks viruses in wastewater, we have a short documentary on that. There’s a link to it in the transcript for this episode.

Lewis: It’s fascinating. Take the plunge!

Fischman: Your Health, Quickly is produced by Tulika Bose, Jeff DelViscio, Kelso Harper, Carin Leong, and by us. It’s edited by Elah Feder and Alexa Lim. Our music is composed by Dominic Smith.

Lewis: Our show is a part of Scientific American’s podcast, Science, Quickly. Subscribe wherever you get your podcasts. If you like the show, give us a rating or a review!

And if you have ideas for topics we should cover, send us an email at Yourhealthquickly@sciam.com. That’s your health quickly at S-C-I-A-M dot com.

I’m Tanya Lewis.

Fischman: I’m Josh Fischman.

Lewis: See you next time.