On this episode I explain how a healthy vaginal microbiome can help protect you from sexually transmitted diseases caused by viruses like HIV, HPV, and HSV. It’s all about creating a healthier host so that we can be more resilient to pathogens – and these methods that our microbes use to defend us apply to STDs as well as diseases like COVID.
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On today’s show, we’re going to be talking about the vaginal microbiome, but this show is for you even if you don’t have a vagina. I’m going to explain how your microbes protect you from viral infections, and these are general principles that apply throughout your body. This episode is all about creating a healthier host (and by host, I mean us – our bodies) so that we can be more resilient to pathogens. So stick with me whether or not you have a vagina, because I promise you there is so much useful information in this episode! I’m a gastroenterologist, so I’m all about the gut. But the vagina is the digestive tract’s closest next door neighbor, and like the gut, it also has a booming microbial community that’s intimately involved in its health and wellbeing. To illustrate just how important that community is, let me tell you about a patient of mine, Marissa.
Marissa had been my patient since I diagnosed her with Crohn’s disease at 16. She’d been on tons of antibiotics as a child for strep throat, and again in her teens for acne. I remember Marissa’s first appointment with me after she got her driver’s license. She swaggered into my office proudly dangling her car keys, and on her own for the first time, without her parents hovering nearby. Unfortunately, Marissa’s first time having sex was not nearly as triumphant. She went off to college in Boston, joined a sorority, decided to major in medieval studies, met a nice guy named Bruce, fell in love, lost her virginity, and came home with a painful case of genital warts.
Since she didn’t have a primary care doctor, her parents called me. They wanted to know why this had happened, especially since Marissa had only ever had sex that one time with Bruce. The fact that 75% of sexually active people will get human papilloma virus (HPV) – the organism that causes most genital warts – didn’t make them feel better. They didn’t care about the 40 or so million other Americans with HPV who were mostly asymptomatic or dealing with mild infections. And although they chalked it up to extraordinarily bad luck, they still felt that it was somehow unjust that theirdaughter had developed genital warts after having sex just one time.
But was it just bad luck that Marissa ended up with a sexually transmitted disease after her first (and only) sexual encounter, or were there clues in her background of excessive antibiotic use, autoimmune disease, and frequent douching that could help explain why HPV had chosen to take up long-term residence in her particular vagina?
To understand why Marissa got genital warts after being exposed just that one time to HPV, you need to understandwhat’s going on in the vaginal microbiome – the trillions of microbes that live in the vagina. Like the gut, the vagina is lined by a membrane and has a protective mucus layer that can trap or repel invaders. But unlike the gut, where high microbial diversity is a sign of health, in the vagina, low diversity is the currency, and one single species reigns supreme.
A healthy vagina is dominated by a type of bacteria called Lactobacillus, and their special skill is that they produce large amounts of lactic acid that can inactivate viruses. Lactobacillus bacteria can literally stop STD-causing viruses in their tracks, protecting you from coming down with a sexually transmitted disease. Vaginas lucky enough to be fortified by large amounts of Lactobacillus are much harder for viruses like HIV, HPV, and HSV to penetrate.
In a healthy vagina, somewhere between 60 and 90% of the bacteria are Lactobacillus species. We do see some variation among different races with Caucasian and Asian women tending to have slightly higher percentages of Lactobacillus compared to Hispanic and Black women but regardless of race, more than 50% is definitely the norm. In an unbalanced vaginal microbiome, we see a much lower percentage of Lactobacillus – usually under 30%, with microbes like Gardnerella, Prevotella, and Mycoplasma making up the difference. Now what I want you to keep in mind is that these other bacteria are all normally present in the vagina, but at much lower levels. They’re not particularly pathogenic, they simply lack the acid-producing skills of Lactobacillus, and as a result, they create a more hospitable environment that’s ideal for viruses to replicate and flourish, because acidic environments are much harder for viruses to penetrate.
And this is a key point because chemical warfare – like making acid – is one of the ways your body protects you from pathogens. We see the same thing in the stomach, where gastric acid can inactivate the spike protein on SARS-CoV-2 and that’s why we see a two to four times higher risk of COVID in people taking acid blocking drugs like proton pump inhibitors.
In the vagina, that low Lactobacillus state that puts you at greater risk for viruses has a name: it’s called bacterial vaginosis or BV – and it’s a chronic inflammatory condition, and the most common reason women see their gynecologist. Having BV also puts you at risk for lots of other problems, including urinary tract infections, sexually transmitted diseases, pelvic inflammatory disease, infertility, premature deliveries, low birth weight babies, and miscarriages. If you have BV, regardless of whether or not you’re symptomatic, you’re not just more likely to develop an STD, you’re also more likely to pass one on to your partner, so it’s problematic for penises and other vaginas too.
If you go in to see your gynecologist complaining of the typical off-white fish-scented BV discharge, you’ll almost certainly walk out with a prescription for an oral or topical form of the antibiotic metronidazole (you’ll probably get a prescription for something called Metro gel). After a few days, you’ll be thrilled that your vagina seems back to its normal happy self. Unfortunately, that honeymoon will soon be over, because while metronidazole can get rid of the excess Prevotella and Gardnerella bacteria, it also destroys your Lactobacillus population, leading to a vicious cycle of BV recurrence. So you suppress the bad bacteria, but you also decrease the good bacteria, and then as everything grows back, it continues to be really imbalanced. The irony is that overly enthusiastic use of antibiotics is what usually causes BV in the first place, so it’s not surprising that applying more of the cause does not lead to a cure.
We’re so conditioned to believe that antibiotics are helpful, it can be hard for us to accept that they can make us more susceptible to infection. BV is a classic example of how wiping out essential bacteria like Lactobacillus can make it easier for viruses to penetrate your vagina. Had Marissa been aware that the years of antibiotics she took for acne in high school would lead to a diagnosis of BV, and increase her odds of genital warts, she would probably have declined the prescription from her dermatologist. Like BV, acne is a state of microbial imbalance, not infection, and while an antibiotic may temporarily help get rid of pimples, it frequently leads to unanticipated vulnerabilities down the road. Your face may seem pretty remote from your vagina, but your entire microbiome is synergistically connected, and disrupting one community can lead to disarray in others.
Treating microbial imbalance with antibiotics can make you more susceptible to pathogens because it wipes out the essential bacteria that help to protect you. We see almost five times higher rates of Rotavirus and more severe infection in children who have recently been treated with antibiotics and are missing some of those crucial protective bacteria. The same mechanism of bacterial protection is also true for other viruses like influenza, with increased susceptibility and worse symptoms when antibiotics precede the viral illness.
Millions of people are exposed to HIV, the virus that causes AIDS, or herpes simplex virus, the virus that causes oral and genital herpes, on a regular basis, but many never develop symptoms. Here too, we can predict chronic viral infection based on what the vaginal microbiome looks like. BV (a disrupted vaginal microbiome) is associated with a 60% increased risk of getting HIV after exposure, and more shedding and transmissibility in those who have it. In a study of young South African women, those with vaginal dysbiosis were four times more likely to get infected with HIV. Of course, avoiding unprotected sex is still absolutely the best defense, but having an intact internal army of virus-slaying bacteria also helps.
In Marissa’s case, there were a couple other vulnerabilities that put her at increased risk for genital warts: having intercourse for the first time can cause tears in the vagina. Those tiny openings make it easier for HPV and other viruses to get inside and set up shop, and emphasize the importance of intact physical barriers, especially for organs like the vagina and gut that are in contact with the environment.
Another vulnerability was the medications Marissa was taking. Her autoimmune disease was well controlled, but at a cost: the drugs that kept her Crohn’s symptoms under control by suppressing her immune system also put her at increased risk for HPV because her immune system was compromised, making it less able to fight pathogens. Another big problem was Marissa’s douching, which disrupts the vaginal microbiome and can double the risk of STDs. Introducing chemicals into delicate ecosystems like your vagina, in an effort to cleanse, refresh, or “improve” your body’s natural state usually produces the opposite effect: microbial destruction and more problems. Your vagina is the ultimate self-cleaning oven, and while it’s not supposed to be fish-scented, it’s not supposed to smell like a summer’s eve either.
Your bacteria can work for you or against you – having too much of the wrong species, and not enough of the right, can create an environment that makes it much more likely you’ll become infected after exposure to a virus. Instead of trying to “cleanse” organs that aren’t dirty, you should focus on maintaining and bolstering your natural defenses by nurturing the inhabitants of your nooks and crannies.
In Marissa’s case, a boatload of antibiotics depleted her protective Lactobacillus species and set her up for BV; frequent douching further disrupted her vaginal microbiome; virginal tearing of her vaginal lining compromised her physical barrier; and medications for her chronic autoimmune disease weakened her immune defenses. All of these factors, most of which she was completely unaware of, created a perfect storm for viral penetration, replication, and chronicity.
I want to leave you with three takeaways about resisting viral infections:
- Exposure on its own is not what makes you sick – it’s compromised host defenses like not enough healthy bacteria, or a damaged lining, that ultimately turn an infection into a disease.
- If you’re treating microbial imbalance like BV, acne, or any other form of dysbiosis with antibiotics, immune suppression, or harsh chemicals, you’re making yourself more susceptible to viral infections by weakening your bacterial army.
- The sustainable – and successful – way to correct an imbalanced microbiome is repopulation – increasing your healthy species of bacteria, instead of focusing on eradication. In the case of BV, that may mean using Lactobacillus vaginal suppositories, and making some dietary changes like eating more fermented foods and cutting down on refined sugar – instead of antibiotics.
So that’s it for this edition of the Gutbliss podcast on the vaginal microbiome and how it can protect you from viruses.
