Infectious Dose

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

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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.

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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

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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

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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.

In this episode of Infectious Dose, Heather explores the infectious disease risks that follow hurricanes, tropical storms, and flooding events. Learn how severe weather changes exposure pathways for pathogens already present in our environment and why recovery can create unique health challenges long after the rain stops.

Topics include:

• Floodwater and wound infections
• Vibrio vulnificus and coastal flooding
• Leptospirosis and rodent exposure
• Mold and respiratory risks during cleanup
• Mosquito blooms after heavy rainfall
• Food and water safety after power outages
• Building an infectious disease-informed hurricane preparedness kit

Plus: A free downloadable Infectious Disease Hurricane Preparedness Guide with checklists, safety tips, emergency reference formulas, and a personal medical information worksheet. Download in companion blog post at Infectious Dose.

The storm isn't always the biggest health risk. Sometimes it's the week after.

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Introducing Outbreak Watch by Infectious Dose. When major outbreaks evolve quickly, Heather will occasionally release these extra episodes featuring timely updates and systems-focused analysis.

In this first Outbreak Watch episode, we examine the rapidly escalating Bundibugyo Ebola outbreak in eastern DRC and Uganda alongside the continuing Andes hantavirus cluster linked to the MV Hondius cruise ship.

We break down the latest WHO numbers, why Ebola transmission is accelerating through conflict-affected mining corridors, what new genomic and geospatial analyses reveal about the outbreak’s spread, and why public-health responders are struggling to contain it amid violence and instability.

We also discuss the newest hantavirus cases emerging internationally weeks after passengers returned home, why the slow appearance of additional cases is expected for Andes virus, and how this cluster has already affected global biocontainment logistics.

Finally, we look at the U.S. decision to send exposed Americans to a quarantine facility in Kenya instead of bringing them home for monitoring and treatment — and what that reveals about confidence in domestic public-health systems.

Pathogens don’t create emergencies in isolation. They exploit the vulnerabilities we leave open for them.

A nurse in Louisiana receives an HIV diagnosis that doesn’t make sense.

No clear exposure. No obvious source. And eventually, investigators begin to suspect something far more disturbing.

In this episode of Outbreak After Dark, Heather and Kate explore the real case that brought forensic virology into the courtroom for the first time. Through genetic sequencing and phylogenetic analysis, scientists traced the relationships between viruses to help prosecutors build a criminal case against a physician accused of intentionally infecting his former partner.

How can a virus become evidence?
What can viral evolution reveal?
And how do you explain that science to a jury?

This is the story of the case that asked whether a virus could testify.

Topics include:

• Forensic virology
• Viral mutation and transmission
• Scientific evidence in criminal court
• Daubert standards
• The Richard Schmidt case

And because this is Outbreak After Dark, there’s also a menu:
• Chain of Custody cocktail
• Cold Case File mocktail
• Trace Evidence Bites
• Gel Run Layers dessert

All recipes and citations in the companion blog post at infectiousdose.com

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