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The Man Who Caught the Mahoney Strain

Three healthy children next door carried the most lethal poliovirus ever found, and a forgotten scientist caught it in a jar. Why does the world remember Jonas Salk but not the man whose strain became both his vaccine and a disaster?

4 chapters · 9 sourcesBy EricPublished November 5, 2026

Questions about this story

What is the Mahoney strain of poliovirus?

The Mahoney strain of poliovirus is an exceptionally virulent wild Type One poliovirus isolated in 1941 from three healthy children in Akron, Ohio. Cultured by researcher Walter Mack, it produced intense antibody levels and became the Type One component of Jonas Salk's polio vaccine, despite being recognized as the most violently paralytic wild poliovirus ever cultured.

Who discovered the Mahoney strain of poliovirus?

Walter Mack, a research associate working with Dr. Thomas Francis Junior from the Michigan School of Public Health, isolated the Mahoney strain in 1941. Mack collected stool samples from three asymptomatic Mahoney children who lived next door to a family devastated by polio, blended the samples with saline and ether, and proved the presence of live virus.

Why did Jonas Salk choose the Mahoney strain for his polio vaccine?

Jonas Salk chose the Mahoney strain for Type One polio because it grew aggressively and stimulated very high antibody levels in recipients. Although researchers Albert Sabin and John Enders urged him to use a milder strain, Salk insisted that treating the virus with formalin would safely inactivate it, eliminating any risk from its extreme virulence.

What happened during the 1955 Cutter incident involving the Mahoney strain?

In April 1955, manufacturing filters at Cutter Laboratories failed to clear protein clumps, leaving live Mahoney virus shielded inside batches of Jonas Salk's vaccine. Approximately 200,000 children received the tainted vaccine, leading to 200 cases of permanent paralysis and 10 deaths, while prompting countries like Sweden to reject vaccines containing the Mahoney strain.

More about the projects he worked on and his life and history?

You asked about Walter Mack's career beyond that Akron backyard, and his work actually took an unusual turn. After Ann Arbor, Mack moved to Michigan State University as a professor of microbiology and public health. He spent decades pioneering environmental virology, tracking how poliovirus and other enteric pathogens survived in municipal sewage and contaminated waterways. Tracking sewage viruses isn't glamorous, but he was literally mapping how public sanitation stopped outbreaks in real time. Exactly. He stayed out of the celebrity spotlight, publishing on water safety until he retired to Holland, Michigan, to photograph sand grains and garden. So, back to how we wrapped things up: Mack quietly outlived the polio titans, leaving behind a monumental legacy from that one Ohio summer.

Read the full transcript

Period: 1941 - 1955 · 5 minutes · English · two hosts

c. 1941 CE

The Kline Children

Akron, Ohio, August 1941
Five siblings, all operated on the same day
Three dead within a week

Ada: It's late August, nineteen forty-one, in Akron, Ohio. Inside one house, five children, aged six to eleven, lie paralyzed. Three of them will be dead within a week. Their parents are untouched. Their baby brother, two and a half, is untouched.³⁵

Theo: And the five who got sick, what did they all have in common?

Ada: On the twenty-second of August, all five had gone to a clinic together for routine tonsillectomies and dental extractions. Nine days later, the illness came.³

Theo: So the surgery itself did something. That's the thread the whole story hangs on.

Ada: It is. And the man who pulled that thread spent sixty more years almost entirely forgotten. I'm Ada.

Theo: And I'm Theo. Welcome to Historai. Let's meet him.

c. 1941 CE

Polio Provocation

Neighbors blamed ether or a family hex
Francis and Mack traced the real cause
Throat surgery opened a path for latent virus

Ada: The neighbors had an explanation. Some whispered the surgical ether had been poisoned. Others said the family was cursed, a hex that struck the children and spared everyone else.

Theo: I mean, look at it from their side. Five kids in one house, parents fine, the baby fine. A curse almost makes more sense than anything.

Ada: The local pediatrician, John Toomey, reported real panic in the community. So he and his colleague Carl Krill called the National Foundation for Infantile Paralysis for help.³

Theo: And who turned up?

Ada: Doctor Thomas Francis Junior from the new Michigan School of Public Health, and a young research associate named Walter Mack. They came to map the contacts and find the mechanism.³⁴

Theo: So what was it, if not a curse?

Ada: Provocation. The record showed the surgery had torn open nerve endings in the throat, giving a latent virus a direct road into the central nervous system. They published it in the Journal of the American Medical Association in nineteen forty-two. The polio was already in them; the knife opened the door.³

c. 1941 CE

The Mahoney Strain

Isolated from three healthy neighbor children
Paralyzed lab monkeys on injection
Named for the family that carried it

Ada: Right next door lived the Mahoney family. Three children, ages ten, eight, and three, who played constantly in the shared yard with the sick family. And they were perfectly healthy. No fever, no stiff neck, nothing.¹⁵

Theo: So Mack wondered if the healthy kids were secretly carrying it.

Ada: Exactly. He and Francis collected stool samples from all three Mahoney children, pooled them, blended them with saline and ether, and spun out the bacteria to leave only virus.¹⁴

Theo: And then?

Ada: Back in Ann Arbor, Mack injected the filtered extract into rhesus monkeys. The monkeys collapsed with flaccid paralysis. The healthy children had been carrying a live, ferocious virus. It went into the catalogue under their name: the Mahoney strain.¹³

Theo: The popular story later called that a kind of gift, didn't it? Healthy children handing science a blessing.

Ada: That's the gentle version. The virology records say the opposite. Mahoney turned out to be the most violently paralytic wild poliovirus ever cultured. Albert Sabin called it a ferocious killer that could invade muscle directly.⁵⁸

c. 1955 CE

Mahoney, Salk, and the Cutter Disaster

Salk chose Mahoney for Type One
Cutter's live virus paralyzed hundreds
Mack died in 2008, largely unrecognized

Ada: Jump to nineteen fifty-five. Edward R. Murrow and the American press crown Jonas Salk a lone miracle worker who conjured the vaccine from nothing.

Theo: And the truth is he inherited the ingredients.

Ada: He did. Salk needed one strain for each of the three polio types. For Type One, which causes over eighty percent of epidemics, he chose Mahoney, Mack's isolate, straight from the Michigan library. It grew aggressively and triggered huge antibody levels.¹⁵

Theo: But that's the killer strain. Didn't anyone object?

Ada: Sabin and Enders begged him to drop it for a milder strain. Salk said formalin would fully kill the virus, so its virulence wouldn't matter.⁵⁸

Theo: And then Cutter Laboratories happened.

Ada: In April nineteen fifty-five, children started getting paralyzed in the exact arm they'd been injected in. Cutter's filters had left live Mahoney virus shielded inside protein clumps. Around two hundred thousand children got it; two hundred were permanently paralyzed, and ten died. Sweden refused the vaccine over Mahoney entirely.⁵

Theo: And Mack? The man who pulled the first thread?

Ada: He went to Michigan State, studied viruses in sewage, retired to Holland, Michigan, and photographed grains of sand. Neighbors remembered him injecting dandelions with hypodermic syringes, joking he couldn't imagine life without them.²⁷

Theo: There's a wild internet claim he was a secret Pentagon bioweapons man harvesting fetal brains.

Ada: The archives say he was an environmental microbiologist studying wastewater. Nothing more. He died in two thousand eight at ninety-seven, having outlived Salk, Sabin, and Francis, and nearly every history that should have named him.²⁷

Theo: And whenever you want to ask us more about any of this, you can stop the episode and do exactly that.

Ada: The healthy children next door carried a killer, a quiet man caught it, and the whole world's vaccine grew from it. Thank you for riding along, Eric.

Theo: This was Historai, where history answers back.

Research record

Sources

si.eduMuseum or archive
stacks.cdc.govMuseum or archive
researchgate.netAcademic
cdn.who.intWeb
dokumen.pubWeb
journals.asm.orgWeb
legacy.comWeb
forbes.comWeb
The Polio-Biowarfare Connection - Debbie Lerman's SubstackWeb