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

June 10, 2026 39 mins

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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A new Ebola outbreak is unfolding in Central Africa — this time caused by Bundibugyo ebolavirus. As cases rise in the Democratic Republic of the Congo and Uganda, fear and misinformation are spreading too.

In this episode, we break down:

  • What Ebola actually is
  • How Ebola spreads — and how it doesn’t
  • Why healthcare workers and caregivers are at highest risk
  • What happens inside the body during Ebola infection
  • Wh...
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Last week, the central question surrounding the MV Hondius outbreak was whether Andes virus was spreading person-to-person at all.

This week, the evidence shifted.

In Part 2 of Hantavirus on the High Seas, we revisit the major questions from last week’s episode and examine what new genomic data, case timelines, and public-health guidance now suggest about the outbreak. We break down what changed, what remains uncertain, and w...

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A hantavirus outbreak linked to a cruise ship has triggered fear, speculation, and growing debate online about whether the virus could be spreading person-to-person.

But what do we actually know right now?

In this episode, Heather breaks down the current hantavirus cruise cluster through the lens of science communication and uncertainty. Rather than focusing only on the facts of the outbreak, this episode explores a bigger question...

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Imagine getting sick in the 1700s—before microbes were discovered, before antibiotics, and before infection had a clear cause.

In this Outbreak After Dark episode, we explore the strange, unsettling, and sometimes surprisingly insightful treatments used to fight disease in the pre-germ theory era. From bloodletting and mercury to tobacco smoke enema...

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There’s a virus you probably already have.

Epstein–Barr virus infects nearly 95% of adults worldwide. For many, it shows up once—fatigue, a sore throat, maybe a diagnosis of mononucleosis—and then disappears.

But EBV doesn’t disappear.

It stays,...

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Murine typhus is a flea-borne bacterial infection that continues to circulate in parts of the United States, particularly in urban and suburban environments. But it’s often missed—because its symptoms are nonspecific, its rash may be subtle or absent, and it doesn’t fit the diagnostic patterns clinicians expect.

In this episode, we e...

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One year in, Heather steps back to reflect on what this podcast has become—and what changed along the way.

What started as a focus on clear, accurate science grew into something more layered: an exploration of how trust, systems, and lived experience shape the way people understand infectious disease. It also opened the door to creative storytelling, immersive formats, and conversations that challenged her own assumptions.

Th...

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You’re about to step inside a BSL-4 lab.

Not a tour. Not an explanation.

An experience.

You’ll move through clearance. Suit up. Connect to air. And cross the threshold into one of the most controlled environments in the world.

Inside, the work is methodical. Quiet. Precise.

And everything you think you know about these labs… starts to shift.

Put your headphones on. And step inside.

More information and resources ...

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The plague doctor: a symbol of fear, medicine, and mystery. But were they really the heroes we imagine—or something more complicated?

In this Outbreak After Dark episode, we explore the real history behind the iconic beaked mask. From medieval theories of “bad air” to the rise of quarantine systems and early public health policy, we follow...

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What if the biggest misunderstandings about vaccine safety aren’t just about the science—but about how the system communicates it?

In this updated guided tour of the Vaccine Safety Series, Heather maps the episodes that break down how vaccines are tested, monitored, and evaluated—and where communication and institutional failures have contributed to confusion and mistrust.

This episode is designed to help you navi...

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When we talk about misinformation in public health, we usually imagine social media, conspiracy theories, or individuals misunderstanding science. But what if some of the most influential misinformation starts somewhere else?

In this episode of Infectious Dose, Heather speaks with biomedical researcher Dr. Mark Ungrin about how scientific ideas mov...

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Mpox isn’t just a headline from 2022.

In this episode, we explore what scientists have learned about mpox since the global outbreak — from how the virus moves through the body to why its lesions can be so painful. We break down the biology of orthopoxviruses, the surprising role of human immune enzymes in shaping viral evolution, and the e...

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What if attraction isn’t entirely yours? In this Outbreak After Dark episode, Heather, Kate, and Sam gather around the campfire to explore the parasites, fungi, and viruses that manipulate behavior in the name of survival. We’re talking:

  • Toxoplasma gondii, the parasite that dampens rodents’ fear of cats
  • The lancet liver fluke, which turns ants into grazing bait
  • Ophiocordyceps, the real-life “zombie ant&...
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Nipah virus scares virologists, and for good reason. It infects endothelial cells and neurons. It can cause fatal encephalitis. It spreads from bats to humans, and sometimes between people. So why does it keep burning out? In this episode of Infectious Dose, we examine:

  • Henipavirus biology and receptor usage (eph...

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Syphilis is back—and it never really left. In this episode, we break down how a curable, preventable infection is resurging to cause a public health crisis across the U.S., and globally, especially among pregnant people and newborns. We unpack the science behind Treponema pallidum, the public health failures driving the crisis, and why trust in health systems is still broken—from ...

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This short, standalone episode is a statement of ethics.

It explains why this podcast will not remain silent in the face of state violence, the dismantling of public health, and the normalization of harm against vulnerable people. It clarifies the ethical boundaries that guide the work behind Infectious Dose: that science is for everyone, but cruelty, authoritarianism, and the protection of abuse are not neutral positions.

This epi...

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