Infectious Dose

Infectious Dose

Infectious dose is the shot of science you need to protect yourself from misinformation. Heather McSharry, PhD, an expert in viral pathogenesis, brings her blog to the airwaves to help bridge the dangerous gap between the science of infectious diseases and public misperception. On the podcast website, infectiousdose.com, all episodes have corresponding blog posts with the information contained in the episode along with links or PDFs for all sources used. To prevent unwelcome surprises, episodes with limited, mild profanity are marked as explicit. *Podcast intro and outro music are adapted from Heather Nova’s song, I Miss My Sky. Used with permission.

Episodes

August 28, 2026 21 mins

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 clim...

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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 stor...

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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...

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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...

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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.

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August 7, 2026 18 mins

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 wh...

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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 t...

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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 con...

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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 infectio...

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July 17, 2026 14 mins

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 ...

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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-lon...

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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 Nigh...

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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 fo...

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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...

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June 19, 2026 19 mins

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...

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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 ...

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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 myst...

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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 wou...

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May 28, 2026 17 mins

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 ...

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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 be...

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