Infectious Dose

In this episode of Infectious Dose, we follow the dengue transmission chain from traveler to mosquito to locally acquired infection. How does dengue become infectious inside a mosquito? Why do most imported infections go nowhere while some seed outbreaks? What can mosquito traps and viral genomes tell investigators? Why can a jump in reported cases give a misleading picture of when infections actually occurred? And at what point would local transmission become something more persistent? Using Florida's current dengue outbreak as a case study, we'll explore the space between introduction, local transmission and establishment and why a growing outbreak does not automatically mean dengue has become endemic. Full annotated citations and additional resources are available in the companion blog post at InfectiousDose.com . You can also sign up there for Field Notes, the Infectious Dose newsletter, for outbreak updates, new episodes and other infectious-disease stories.

A fungus appears in hospitals on different continents. You assume it started somewhere and spread. Then scientists sequence it and discover that the story is much stranger. This week on Infectious Dose, we're exploring the strange emergence of Candida auris, now taxonomically known as Candidozyma auris. We trace the organism from its description in Japan to the discovery of genetically distinct lineages emerging in different parts of the world, and ask a question scientists still haven't completely answered: why did this fungus seemingly become a human pathogen in several places within such a short period of time? Along the way, we'll explore why C. auris is so well-suited to healthcare environments, how people can carry it without becoming sick, why it can persist on surfaces and resist ordinary infection-control measures, and what happens when it also becomes resistant to the limited antifungal drugs available to treat invasive infections. And ahead of Fungal Disease Awareness Week, we'll look at the larger lesson of the C. auris story: fungi deserve a much bigger place in how we think about emerging infectious disease. Full annotated citations and additional resources for this episode are available in the companion blog post at InfectiousDose.com .

Put on a coat. Dry your hair. Don’t sit on that toilet seat. Green snot means antibiotics. And if food hits the floor, you have five seconds. But how much of the infectious-disease wisdom we inherited from our parents is actually true? In this episode of Infectious Dose, we put some of the classics under the microscope: whether being cold can really make you sick, what green mucus actually tells us, why fever isn’t a good measure of how sick someone is, whether public toilet seats deserve their reputation, what the five-second rule gets wrong, and why a case of head lice does not require decontaminating your entire house. It turns out many of these myths started with perfectly reasonable observations. The problem came when generations of parental anxiety tried to explain the biology. Mom wasn’t necessarily wrong about what she saw. She was just wrong about the rhinovirus waiting for you on the porch. Want to dig into the science behind this episode? You’ll find the full companion blog post , including annotated citations and links to the research, at InfectiousDose.com. While you’re there, you can also sign up for Field Notes , the free Infectious Dose newsletter, for more infectious-disease stories, outbreak updates, and curiosities between episodes.

In this Outbreak Watch, we return to the outbreaks and signals we’ve been tracking...and several have changed. New genomic evidence is revealing the hidden early months of the DRC’s Bundibugyo Ebola outbreak, while Uganda has successfully ended transmission across the border. New World screwworm is worsening in Sonora as cattle imports into Arizona resume, and COVID-19 is climbing again across the South amid changes to how CDC categorizes and displays wastewater activity. We also check in on measles, Cyclospora, H5 avian influenza, Vibrio vulnificus, mpox, Oropouche, and other signals on the board—and close the loop on the quarantined riverboat near Kinshasa. Full citations in companion blog post at Infectious Dose. Subscribe to Field Notes to continue the conversation around episodes and weekly outbreak updates.

Somebody's roommate's cousin definitely knows the person this happened to. This month on Outbreak After Dark, pull up a chair for an evening of infectious-disease urban legends. Heather investigates the infamous “Welcome to the World of AIDS” story and infected-needle scares, whether you can really get crabs from a toilet seat, and the long-running warning about fatal leptospirosis from rat urine on soda cans. Each story gets a Campfire Verdict as we separate genuine biology from folklore and ask what happens when something that could happen gets transformed into a story people swear happened. Then Heather and her unusually quiet cardboard cohost, CK, play Construct a Contagion, building an infectious-disease urban legend from scratch and testing their creation against real microbiology. Because possible, plausible, and proven are three very different things. Citations and resources can be found in the companion blog post at Infectious Dose.

What changes when the sun goes down? In the final episode of From Sunrise to Starlight, we're heading down a summer trail as dusk gives way to darkness, following the microbes—and the vectors and hosts that carry them—into the night. We'll explore why different mosquitoes keep different schedules, how ticks find hosts, what wildlife encounters actually mean for zoonotic disease risk, and how artificial light can alter nighttime ecology. Then we'll emerge from the woods beside a dark lake, turn off the flashlight, and look up. Because infectious-disease risk isn't simply about which pathogens are present. It's about encounters: where they happen, when they happen, and how microbes, vectors, hosts, and human behavior come together. Night Hike: Following Microbes Into the Dark closes our August journey from the first light of morning to a lake beneath the stars. All citations in the companion blog post at Infectious Dose.

It’s afternoon in our journey From Sunrise to Starlight, and we’re spreading out the picnic blanket. This week, we’re following the hidden microbial pathways running through a summer meal. From farms and kitchens to the cooler, the blanket, and eventually us. We’ll explore how foodborne pathogens such as Salmonella, Listeria, Cyclospora, and norovirus reach our food, what happens as the cooler warms, and how hands, utensils, flies, ants, and even a shared bag of chips can turn a picnic into a transmission network. Plus: Does the five-second rule work? Can ants actually contaminate your food? Is mayonnaise really the problem with potato salad? And when the picnic is over, which leftovers should come home? Pull up a corner of the blanket. Lunch is served. See companion blog post for citations. Subscribe to Field Notes to continue the conversation.

The guy in the white house signed a new executive order changing federal childhood vaccine policy. So what actually changed and what does it mean for families? In this bonus Booster Dose episode, Heather separates the executive order itself from claims made during its announcement and break down what we know right now. She covers the new categories of childhood vaccine recommendations; the proposal to separate MMR into individual measles, mumps, and rubella vaccines; the directive calling for childhood immunizations to be administered at separate medical visits “to the maximum extent feasible”; potential effects on vaccine access and insurance coverage; what states can—and don’t have to—do in response; and what parents should know about upcoming vaccination appointments. She also addresses claims he made about MMR safety, the amount of vaccine children receive, giving multiple vaccines at once, and autism and point you toward previous Vaccine Safety Files episodes for deeper dives into the evidence. This policy is still developing. This episode reflects what we know as of August 10, 2026. Relevant Vaccine Safety Episodes: Measles and MMR Too Many Too Soon? Vaccines & Autism

Ebola nears 4,000 confirmed cases in the Democratic Republic of the Congo, New World screwworm continues circulating in Texas, and the U.S. cyclosporiasis outbreak is expanding. In this Outbreak Watch, we look at what has changed and what the evidence actually tells us, including why there’s currently no evidence that mutation explains the severity of the Ebola outbreak and why wildlife surveillance may be crucial to understanding screwworm transmission. Then we zoom out for Global Signals and Surveillance Milestones: Chile’s nationwide hantavirus response, H5 avian influenza, Oropouche virus, a 30-year measles high in the United States, and rising Hansen’s disease cases in Florida. All Citations in companion blog post at the website. Subscribe to the free Field Notes newsletter to continue the conversation around the weekly episodes.

A summer morning at the lake is about swimming, skipping stones, dragonflies, and family memories, but it's also the perfect opportunity to explore one of nature's most fascinating invisible ecosystems. In this episode, we're diving beneath the surface of freshwater lakes to discover how microbes respond to changing environmental conditions throughout the day. We'll discuss: Why swimmer's itch is caused by a confused bird parasite—not dirty water How cyanobacterial (blue-green algae) blooms develop and why not all blooms are toxic The real story behind Naegleria fowleri, the so-called "brain-eating amoeba," and why infections remain extraordinarily rare How sunlight, temperature, wind, and wildlife shape lake microbial communities How public health agencies monitor recreational waters The growing role of citizen science in protecting lakes and rivers Whether you're a swimmer, paddler, angler, pet owner, or simply someone who loves spending time outdoors, this episode will give you a new appreciation for the remarkable—and mostly unseen—life beneath the water's surface. All citations and resources in the companion blog post on the website. Subscribe to the free weekly newsletter, Field Notes , to continue the conversation around each episode.

Medicine. Contraband. Comfort. Step inside a hidden 1920s speakeasy where the jazz is live, the whiskey is illegal, and one of the most surprising chapters in medical history unfolds. During Prohibition, physicians could legally prescribe medicinal whiskey for illnesses ranging from pneumonia and influenza to pain and "nervous exhaustion." At the same time, bootleggers, pharmacists, lawmakers, and patients were all navigating a confusing world where the same bottle could be medicine, commodity, or contraband. In this immersive Outbreak After Dark episode, Heather and Kate explore: Why doctors prescribed medicinal whiskey before antibiotics How Prohibition reshaped medical practice Patent medicines and the blurred line between treatment and marketing Industrial alcohol and the tragic consequences of denaturing What these stories reveal about medicine, evidence, and human behavior Join us for an evening of jazz, secret passwords, and one of the most unusual intersections of infectious disease and American history. Full citations and more at the website . Subscribe to the Field Notes newsletter to continue the conversation and get updates on outbreaks and a peek behind the scenes.

For much of history, entering a hospital could be one of the most dangerous decisions a person could make. Patients survived injuries and operations only to die from infections acquired in the very places meant to heal them. In this final episode of our Turning Points in Infectious Disease series, we explore the revolution that transformed hospitals from centers of disease transmission into institutions designed to prevent infection. Follow the stories of Ignaz Semmelweis, Louis Pasteur, Joseph Lister, and Florence Nightingale as medicine gradually uncovered the invisible world of microbes and reshaped healthcare around one revolutionary idea: the safest infection is the one that never happens. We'll also explore why healthcare-associated infections still occur today and what this history teaches us about the ongoing challenge of translating scientific evidence into everyday practice. Check out the companion blog post at the website for full, annotated citations , historical images, and more. And subscribe to the free weekly newsletter, Field Notes , to continue the conversation, get updates on outbreaks and the infectious disease signals Heather is paying attention to, and get a peek behind the scenes.

In this edition of Outbreak Watch, we provide a current briefing on the major outbreaks unfolding now, including Ebola in the Democratic Republic of the Congo and Uganda, New World screwworm in the United States, and the rapidly growing U.S. cyclosporiasis outbreak. Along the way, we answer the questions listeners are asking most. We also examine several emerging signals, including H5 avian influenza in mammals, the potential for Vibrio vulnificus infections this summer, and why surveillance systems are just as important as laboratories when it comes to detecting outbreaks before they become national emergencies. As always, you'll find annotated references, official dashboards, and links to additional resources in the companion blog post at InfectiousDose.com . If you want the free, weekly companion newsletter to the episodes, Field Notes , subscribe here.

For most of human history, epidemics were something people endured—not prevented. Smallpox alone killed hundreds of millions of people, leaving survivors scarred, blinded, or forever changed. But hidden within that devastation was a remarkable observation: those who survived rarely became sick again. In this episode, we explore the centuries-long journey from variolation to vaccination, following the observations of physicians, the experiences of milkmaids, the bold experiment of Edward Jenner, and the scientific breakthroughs that transformed an idea into one of medicine's greatest achievements. We'll also trace how Jenner's work inspired generations of scientists, eventually leading to vaccines against countless other diseases and the global eradication of smallpox. This episode is part of our July series, Turning Points in Infectious Disease, exploring the discoveries that fundamentally changed humanity's relationship with disease. This week, we examine the moment prevention became possible. For the full list of annotated citations, historical images, and additional resources, visit the companion blog post at InfectiousDose.com . And while you're there, subscribe to Field Notes , our free weekly newsletter featuring an expanded conversation about the episode, outbreak updates, infectious disease signals I'm keeping an eye on, and behind-the-scenes notes from Infectious Dose.

For much of history, disease claimed more soldiers than combat. In this episode of Infectious Dose, we trace the evolution of military preventive medicine—from the Revolutionary War to the present day—and explore how armies came to view infectious disease as an operational threat rather than an unavoidable consequence of war. We'll follow the story through George Washington's smallpox inoculation campaign, Florence Nightingale's sanitation reforms during the Crimean War, Walter Reed and William Gorgas's fight against yellow fever, the development of military vaccination programs, the adenovirus outbreaks that reshaped recruit health, COVID-19 aboard the USS Theodore Roosevelt, and the ongoing influenza outbreak among military trainees at Lackland Air Force Base. It's the story of how prevention became strategy—and why the invisible enemy continues to shape military readiness today. Companion blog post with all citations and resources at Infectiousdose.com Subscribe to the free, weekly Infectious Dose newsletter, Field Notes .

In the mid‑20th century, ranchers across the southern United States watched livestock being literally eaten alive by a flesh‑eating parasite: New World screwworm. This episode tells the story of how an entomologist’s “absurd” idea helped eradicate screwworm from North America, and why that victory is suddenly back in the spotlight as new cases appear in Texas in 2026. We follow the parasite’s biology, the development of the Sterile Insect Technique, the massive binational infrastructure that kept screwworm at bay until it was gutted last year, and the quiet, ongoing work of prevention that most people never see. Along the way, we explore what this outbreak can teach us about public health systems, maintenance versus one‑time “wins,” and why some of the most important turning points in infectious disease are really long‑term commitments. Companion blog post with annotated citations and resources at infectiousdose.com. Subscribe to Heather's free, weekly newsletter, Field Notes , to continue the conversation beyond each episode, get outbreak updates, and see behind the scenes of Infectious Dose.

June's Summer Rain series wraps up with a tribute to Gulf Coast mosquitoes. In this episode of Outbreak After Dark, Heather and Kate explore the anatomy of a mosquito bite—from the moment a female mosquito detects carbon dioxide to the itch that keeps you awake long after she's gone. Topics include: • How mosquitoes find humans • Why only female mosquitoes take blood meals • The surprising anatomy hidden inside a mosquito's proboscis • Why mosquito bites itch • Histamine, nerves, and the science of scratching • Why some people attract more mosquitoes than others • Mosquito-borne diseases and changing mosquito ranges • Practical mosquito prevention tips Plus: a Galveston mosquito disaster and an unexpectedly heated discussion about the plural of proboscis. Recipes for Night Hum, Wheal & Fizz, Grilled Proboscides, and Afterbite are available in the accompanying blog post at infectiousdose.com Subscribe to the free weekly newsletter, Field Notes.

Outbreak Watch returns with updates on three unfolding biological events and the systems responding to them. This week: • The Bundibugyo Ebola outbreak in the Democratic Republic of the Congo becomes the largest on record as contact tracing, clean water access, and response operations face growing challenges. • The Andes hantavirus outbreak linked to the MV Hondius cruise ship is behaving as expected, providing an important lesson in what successful containment looks like. • New World screwworm detections in the United States highlight ongoing debates about surveillance, preparedness, and the challenges of responding to an emerging threat when critical systems must be rebuilt. In this episode, we explore visibility, uncertainty, and the operational realities that shape outbreak response long before most people hear about it. For weekly outbreak updates, subscribe to the free Infectious Dose newsletter, Field Notes , at infectiousdose.com

You can smell rain before it arrives. The air changes. The wind shifts. And somehow, before the first drop falls, you already know a storm is coming. In this immersive episode of Infectious Dose, we explore the science behind that experience. We'll follow a summer storm from distant rain clouds to the microbes living beneath our feet, uncovering the roles of petrichor, geosmin, and the remarkable biology behind one of nature's most beloved scents. Along the way, we'll explore why humans are so sensitive to the smell of rain, how storms become tied to memory, and why a single breath of cool air before a summer downpour can transport us years into the past. Part science story. Part sensory journey. Part summer rain. Experience audio of a real summer storm from Heather's patio Part of our June series: Stories of Summer Rain. Citations in companion blog post at Infectiousdose.com Sign up for the free weekly newsletter, Field Notes

In this episode of Infectious Dose, Heather explores one of the strangest allergic conditions modern medicine has ever identified: a syndrome in which a tick bite can trigger an allergy to mammalian meat weeks, months, or even years later. Why do symptoms often appear in the middle of the night instead of immediately after a meal? How did a cancer drug help scientists solve the mystery? Where does the alpha-gal molecule come from, and why do ticks seem uniquely capable of triggering this unusual immune response? Join us as we follow the trail from the woods to the dinner table and unravel the science behind alpha-gal syndrome. In this episode: • What alpha-gal syndrome is and how it develops • The surprising role of the Lone Star tick • The cancer drug clue that helped solve the mystery • Why reactions are delayed for hours after eating • Diagnosis, testing, and common misconceptions • Living with AGS and preventing future tick bites • Separating evidence from conspiracy theories Part of our June series, Stories of Summer Rain, this episode explores how warm, wet environments shape the ecosystems around us—and how those ecosystems can unexpectedly shape our health. Referenced resources and scientific citations are available at InfectiousDose.com . Subscribe to Field Notes , the free Infectious Dose newsletter, for weekly Outbreak Watch updates and additional resources.