The Outbreak
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It began in July 1933 when Fred Green was hospitalized with fever, headache, and stiff neck—symptoms that quickly escalated to coma and death.
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Soon, more than 1,100 cases were reported, with 200+ deaths that summer.
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Doctors noted that all victims had very high fevers (103°F+), severe headaches, and neurological symptoms.
The Investigation
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The summer had been one of the driest on record, creating perfect conditions for mosquito breeding.
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Washington University’s Dr. Margaret Smith made the breakthrough by identifying mosquitoes as the vector and observing viral markers in patient cells.
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The disease was officially named St. Louis Encephalitis Virus.
How It Works
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The cycle starts when a female mosquito bites an infected bird, then spreads the virus to humans and other animals.
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Humans can’t pass it to each other—mosquitoes are the carriers.
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Mortality ranges from 5–20%, and survivors often deal with lasting effects like tremors, memory problems, and insomnia.
Symptoms & Treatment
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Symptoms appear 7–21 days post-bite, ranging from mild headaches and nausea to meningitis and full-blown encephalitis.
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There’s no cure—only supportive care like fluids, rest, and hospitalization in severe cases.
Then & Now
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Today, SLEV still shows up in the U.S., especially in late summer and fall.
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In 2022, there were 283 reported cases, with 18 deaths.
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Even though cases are rare today, it remains a CDC-reportable disease.
And yes, this story gives us yet another reason to loathe mosquitoes. 🦟
You can find more at:
Twitter: @showme_history
Facebook: ShowMeHistorySTL
Until next time, I’ll see you in the Lou.