April 1, 2020

Covid-19: What We Know Now About Spread, Shedding Period, Symptoms, and Effects of Pollen

A follow-up interview with Heather Zwickey, PhD

This interview was conducted on March 31, 2020.

In this interview Heather Zwickey, PhD, provides an important update about Covid-19 for healthcare professionals. She discusses the concerning fact that people can be asymptomatic for a longer period of time than previously expected and that the viral shedding may take longer as well. She also discusses the connection between pollen allergies and Covid-19, as well as GI symptoms, conjunctivitis, and supporting the gut microbiome. Zwickey is executive program chair and a professor at National University of Natural Medicine in Portland, OR, and also has previous training and experience with infectious diseases.

Approximate listening time: 14 minutes

About the Expert

Heather Zwickey, PhD, earned a PhD in Immunology and Microbiology from the University of Colorado Health Sciences Center with a focus on infectious disease. Zwickey went on to complete a postdoctoral fellowship and teach medical school at Yale University. At the National University of Natural Medicine in Portland, OR, Zwickey launched the Helfgott Research Institute and established the School of Graduate Studies, developing programs in research, nutrition, and global health, among others. She currently leads an NIH funded clinical research training program. She teaches at many universities and speaks at conferences worldwide. At Helfgott Research Institute, Zwickey applies her immunology expertise to natural medicine, with specific interest in the gut-brain axis in neuroinflammation.  


Karolyn Gazella: There is no question that the Covid-19 crisis continues to be a rapidly moving target. Hello, I'm Karolyn Gazella, your host and the publisher of the Natural Medicine Journal, an online peer-reviewed journal for integrative healthcare professionals. Yes, things are moving fast when it comes to Covid-19, but we at the Natural Medicine Journal remain committed to keeping abreast as best we can. Today we're going to be tackling the ever-changing picture of Covid-19 symptoms, as well as new research on pollen counts and Covid-19 and protecting the gut microbiome. My go to expert on this topic continues to be highly respected integrative health researcher and immunologist, Dr Heather Zwickey. If this is your first time listening to Dr Zwickey, she is executive program chair and a professor at National University of Natural Medicine in Portland, Oregon. Dr Zwickey also has previous training and experience with infectious diseases. Dr Zwickey, thank you once again for joining me to talk about this very complex topic.

Heather Zwickey, PhD: Thanks for having me.

Gazella: So let's start by having you give us an update since we last spoke 2 weeks ago. Anything new from your perspective?

Zwickey: Yes, there's a couple of things that are coming out I think that are worth noting for physicians. First, as we're finally hearing, young people also get this virus. They may not die, but many are being hospitalized. And I think as we talked about last time we chatted, the average age was 44 in China, it was not in the 80s. So keep in mind that younger people are still susceptible. And I think one of the biggest updates is the time of exposure to symptoms. We originally thought it was 2 to 3 days, but now we're seeing that it can be anywhere from 2 to 11 days. That's a huge time span. And we don't know why. It could be the number of viral particles that people are exposed to, or it could be various health factors related to the health of the patient. We just don't know. But during that entire time span, people could be asymptomatic and yet be shedding virus.

Gazella: Yeah. That is really important. And it's a good reminder as to why we're focusing on social distancing so aggressively right now. So that's great. And I do want to talk about the symptom profile, but first I want to discuss a brand new study that just came out in the journal Allergy that looked at pollen counts and Covid-19. Now obviously this can affect a lot of patients this time of year who are dealing with allergies. So what's the connection and what should practitioners consider telling their allergy patients about this new information?

Zwickey: So few things to think about with respect to this. The first thing is that people start worrying when they start having symptoms of allergies because many of the symptoms are shared with upper respiratory viral infections. So the stress isn't good. Secondly, we already know that there's a shortage of tests, and if people start worrying that their allergies are Covid-19 they're going to start using tests that we actually need for people who have Covid-19. So that's not good. But from an immunological perspective, the way that we think about this is allergies are a TH2 response. So when you start mounting an allergy response to birch, or ragweed, or any sort of pollen, you need a TH2 response for the allergy response. But what you need to fight the infection is a TH1 response, not TH2.

In some respiratory infections we're seeing that allergies are reducing the proinflammatory response, including the type 1 and type 3 interferons, and that's usually what we see starting to launch the anti-infection response. So if you have allergies, specifically allergies to birch pollen is what was reported in the journal Allergy, you may have less type 1 and type 3 interferons and mount less of an immune response to any upper respiratory infection. So the data that they used actually came from rhinovirus. We don't know exactly what allergies are going to do to a SARS-CoV-2 infection. In young people it could actually minimize their symptoms even more, even though they're infectious. And in older people and higher-risk populations, people who have comorbidities, it could reduce their ability to fight an infection.

Gazella: That's fascinating. Is there any advice that we should be giving patients who have allergies during this crisis?

Zwickey: Yeah, it's interesting. If you just get online and you Google allergies versus Covid-19, one of the things you'll find are symptom comparisons. So if you have allergies, you're probably not going to have a fever. That's the biggest thing. And if you don't have a fever, it's more likely the allergy and not the Covid-19. If you have a fever, then I would start thinking, well, this could be something different. And then if you get the cough that goes with the fever, now is when you start thinking, well, this could be Covid-19. So just get online and look at those symptom pictures and see where you're at. A headache is not a sign of Covid-19, a headache alone. But a headache, a sinus headache especially, may come with your allergies.

Gazella: That's great advice. Should people with allergies stay indoors more on windy days, or is there any lifestyle-based advice?

Zwickey: It's all the same things we've been telling people with allergies for a long time. Yes, you should stay indoor on windy days, you shouldn't open your car windows. Or if you're driving, put the air on recirculate instead of fresh air so that you're not exposed to more and more of that pollen. The other thing you may consider is using a local honey, which usually contains pollen. And we know if you eat the allergen you are less likely to have that TH2 response to it. So, all of those things are true in these cases.

Gazella: Great. Great advice. So let's dig a little bit more deeply into the topic of symptoms. Now, I have to say, I've been fascinated by the fact that Covid-19 has a growing list of really diverse symptoms, in addition to the typical fever and dry cough that you mentioned. For example, I've been reading articles that GI issues can be a symptom. Now, while it's not a primary symptom, patients with a fever and GI issues may have Covid-19. What's this connection all about?

Zwickey: So the same ACE-2 receptors that we've already talked about that are in the lungs and the kidneys are also in the gut. So if you happen to swallow the virus instead of breathe it, it'll infect the gut instead of the lungs. And when you mount an immune response, one of the cytokines that's made in the gut is TNF alpha, and we know that TNF alpha alone can cause diarrhea. Importantly, many people who have GI symptoms can also be shedding virus in stool. And that brings up something else I wanted to mention, the data from the Chinese that are coming out right now are showing that viral shedding is 20 days. It's not 2 weeks, it's 3 weeks.

So think about the fact that we've had people in quarantine for 2 weeks and then we let them go, and they can actually be shedding for another full week. In fact, Chinese scientists said that some patients actually shed up to 37 days. So that's why there's a continued focus on physical distancing. And I'm trying to change the vernacular from social distancing to physical distancing because people need to be social. It's such a good coping skill and I really hope people are communicating with their friends and family.

Gazella: That is a great point. Physical distancing. I'm going to make sure to use that in the future as well. Now, another symptom that's been discussed in mainstream media is pink eye or red eyes. Now this totally makes sense because people touch their eyes pretty frequently, and if they have the virus on their hands, they can infect the eyes. What do we need to know about this symptom when it comes to Covid-19?

Zwickey: So first of all, it's true. There is a conjunctivitis that can be associated with Covid-19, although it's relatively rare. Data coming out of China and Italy suggest it's about 1 in 1,000 will develop conjunctivitis. So the first thing remember as a doc is to treat these patients as Covid-19 patients. They are infectious, they're shedding virus. And a lot of times when we see the red eye we think that it's limited to the eye. It's not. Also remember that this isn't bacterial, so the antibacterial drops that you drop in people's eyes aren't going to work. You're to treat this like you would treat any other Covid-19 infection, and it can be severe. People can develop a lot of inflammation in their eye from this particular virus. So treating inflammation the way you would as a physician is the way to go.

Gazella: Okay, great advice. Now, is it common for a virus to expand its symptom profile like this? Does this tell us anything about the severity or the uniqueness of this particular virus?

Zwickey: Well, it's not so much an expansion of symptoms. These symptoms have been happening all along, they were just happening in much lower numbers, which meant that doctors didn't know if they were unique to individuals or part of the SARS-CoV-2 infection. So until the numbers became really high we weren't seeing them in high enough numbers to report them. So this is kind of a lesson in epidemiology. If there's low numbers, they could be random. When the numbers get higher, now we can form correlations. Now there's another piece of this. Viruses can infect any tissue for which there is a receptor, and for SARS-CoV-2 the receptor, ACE-2, is distributed among many different tissues. And because the receptor's widespread, there's widespread symptoms. We call this tissue tropism, that the virus is attracted to the tissues that express the receptor. Another virus that does stuff like this is measles. Measles binds to 3 different receptors in 3 different tissues, and as a result you see measles in the lungs and the gut, and in immune cells as well. So, it's true for other viruses, it's just that until you get the law of large numbers, we don't see the symptoms appear in high enough quantity to associate it with this particular infection.

Gazella: Okay, great. That was a great explanation. So I want to end our conversation with the gut microbiome, kind of going back to our conversation about GI symptoms. Now, there's a significant connection between the gut, the immune system, and our ability to fight viruses. What steps can we take to help protect and enhance the gut microbiome?

Zwickey: Yeah, this is so true. We know that if you disrupt the gut microbiome, you make anyone, animal, human or insect susceptible to infections. So the A number 1 thing you can do for the microbiome, of course, is eat vegetables, especially vegetables with good prebiotic fibers. I'm thinking onions, Jerusalem artichoke, sunchokes, leeks, garlic. Potatoes are a vegetable, but they're not the best for feeding the microbiome. Although I'd much rather have you eat a potato than a cookie, but I'd rather have you eat asparagus or greens than a potato. The other thing that most of us forget get is spices are prebiotic. So cooking with spices, rosemary, thyme, basil, oregano, cinnamon, all of those things are going to help feed the bacteria in your gut, your gut microbiome. The next thing that many people would think of is probiotics, and I go probiotic first with food. So thinking about keifer, kombucha, sauerkraut, and yogurt. And usually people are going to gravitate towards the yogurt because they like the sweet taste, but remember the sugar isn't good. So if you're going to go for yogurt, you're going to go for the low-sugar versions.

And then probiotic supplements, of course, could be helping the gut for some people. And while it's true that we have shown that probiotics can improve gut health, we don't actually know which probiotics work best with each individual. And remember, each person's microbiome is different, we all have our own ecosystem. So it'll be great when we can individualize them, but in the meantime, I would consider it self-experimentation, that if you're going to try a probiotic and you haven't ever tried one before, if it doesn't make you feel good, stop. That's not your combo and try something different. What you're doing with your gut is you're regulating both your immune system and your nervous system. So 80% of your immune system is in your gut and more than that for your nervous system. In fact, the microbes in your gut are responsible for making much of the serotonin in your body, and serotonin is contributing to your immune response. So, keep in mind that if your gut's not healthy, then even if every aspect of you feels healthy, you're not healthy.

Gazella: Great, great points. Well, once again, Dr Zwickey, this has been very informational. Thank you so much for joining me and keeping us abreast of the various complexities associated with Covid-19. Thank you so much.

Zwickey: You're welcome.

Gazella: So this podcast is brought to you by Natural Medicine Journal. You can find more information at naturalmedicinejournal.com. Thank you for listening. And if you found this information interesting, please share it with your colleagues. Stay safe, everyone.

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