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Published: October 21, 2025
Read Time: 4.9 Mins
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In this episode of Thermometer HQ, I’m joined by disease ecologist Dr. Jon Epstein to unpack a busy week in infectious diseases—from a concerning mpox signal in Los Angeles to mosquito-borne threats popping up across the country—and to close with two stories that connect immunity, pets, and practical prevention.
Mpox Clade I Detected in Los Angeles
Los Angeles reported three mpox cases linked to Clade I, a lineage historically associated with more severe disease in Central Africa. These cases occurred in gay and bisexual men without clear epidemiologic links, suggesting broader spread within a sexual network.
Since 2022, mpox has shifted from sporadic zoonoses to sustained person-to-person transmission, with sexual contact the predominant route in the U.S. The arrival of Clade I matters: while we still need definitive human data on virulence in well-resourced settings, animal models and field observations raise legitimate concerns.
The good news is we’re not helpless—vaccination with JYNNEOS reduces risk, and the same fundamentals of sexual health apply: rapid recognition, testing, and temporary behavior modification until lesions heal. Public health agencies should intensify community-led outreach and low-barrier vaccination, especially in venues and networks where transmission is most likely.
West Nile Virus: A 2025 Outbreak Year in the Upper Midwest
We then took a mosquito-borne tour of the U.S.—an unusual thing to say in late October, but a reflection of how climate and ecology are reshaping risk.
The Minnesota Department of Health has declared 2025 an outbreak year for West Nile virus (WNV), with more than 100 cases and multiple deaths by mid-October, and elevated activity across the Dakotas.
WNV cycles between birds and mosquitoes; humans are incidental hosts, so there’s no person-to-person spread. There’s also no licensed human vaccine or specific antiviral—care is supportive, which is why prevention matters.
Practical steps remain simple and effective:
- Use EPA-registered insect repellents (DEET, picaridin, IR3535, oil of lemon eucalyptus)
- Wear long sleeves and pants at dusk and dawn
- Dump standing water weekly where mosquitoes breed
Clinicians should remember that neuroinvasive disease can present as meningitis or encephalitis; testing CSF for WNV IgM can clinch the diagnosis.
Chikungunya: New York’s First Local Transmission
New York State confirmed its first locally acquired chikungunya case in a Nassau County resident without travel. Aedes mosquitoes—especially Aedes albopictus—are established on Long Island and can transmit chikungunya even in temperate climates.
Introduction can occur via a viremic traveler or an airport mosquito hitching a ride in cargo. While chikungunya rarely kills, it can be profoundly debilitating: acute fever and severe joint pain, followed by months of lingering arthritis.
That burden on quality of life and outpatient care is why surveillance and vector control matter even when case counts are low.
Dengue in Los Angeles: Climate and Mosquitoes Expanding Risk
Los Angeles has now documented another locally transmitted dengue infection, following a string of locally acquired cases in 2024. “Breakbone fever” is aptly named—its severe myalgias and arthralgias are unmistakable.
With warming temperatures and urban heat islands, we should expect more U.S. pockets that are seasonally permissive for dengue, chikungunya, Zika, and malaria.
For clinicians, the takeaway is to broaden differentials: travel history still helps, but “travel” now includes your own ZIP code.
Good News: Early Peanut Exposure Reduces Allergies
Not all our immune stories this week are grim. After guidelines flipped in 2017 to recommend early peanut introduction during infancy, new data show a 43% decline in peanut allergy among children.
This is clear evidence that the immune system learns from safe exposures while we shield against dangerous ones through vaccination.
It’s important not to conflate microbial exposure with infection. Healthy microbial diversity builds tolerance, but viruses like measles remain dangerous. Vaccination and balanced immune “training” go hand in hand.
Pet Superbugs in New York City: What Owners Should Know
Our final topic connected antimicrobial resistance to home life. A New York City study of veterinary lab results (2019–2022) found about 1 in 60 dog and cat samples grew gram-negative bacteria resistant to carbapenems—organisms like Klebsiella, Pseudomonas, and E. coli.
The prevalence was low and stable, but even low levels matter for immunocompromised people.
Practical Advice for Pet Owners
- Talk with your doctor if you’re immunocompromised (receiving chemotherapy, post-transplant, or on immunosuppression).
- Keep pets healthy with regular vet visits and updated vaccines.
- Practice good hygiene: wash hands after handling food, litter, or waste; avoid letting pets lick open skin or your face.
- Therapy animal programs should include infection control protocols to protect vulnerable patients.
The key takeaway: Pets are part of our ecosystem of health. Protecting them protects us.
One World, Shared Health
Globalization and climate change are redrawing disease maps in real time—what was “tropical” is now local. Rare doesn’t mean irrelevant; small risks multiplied across millions create real burdens.
Prevention remains our strongest tool: vaccines where available, testing and early behavior change for STIs like mpox, mosquito control for vector-borne diseases, and antimicrobial stewardship across both human and veterinary medicine.
👉 Watch the full episode on YouTube: https://youtu.be/au1FkXLl7cY
