Field Notes #17: First Watch
- Heather McSharry, PhD
- Aug 5
- 6 min read
In the Margins
While researching this week's episode, one detail stayed with me...that dogs sometimes become sick from harmful cyanobacterial blooms before anyone realizes a lake has become dangerous.
That made me wonder how often a veterinarian is the first person to recognize that something in the environment has changed. And it turns out that sometimes veterinarians are among the earliest to notice unusual illnesses that eventually lead to broader investigations. A cluster of dogs becoming ill after swimming may prompt questions about water quality. Horses developing neurologic disease have helped identify West Nile virus activity. Cats, livestock, wildlife, and companion animals occasionally become the first visible signs that something new is happening before humans are impacted.
The more I thought about it, the more I realized veterinarians aren't unusual in this respect. They're part of a much larger network of people whose jobs place them at the edge of where infectious diseases first appear...not physicians or epidemiologists, but people who spend their days paying close attention to animals, water, food, or communities.
Before there are case counts, there are often people who notices that today doesn't look quite like yesterday.
Underlined
Many of our earliest emerging infection warnings begin with someone whose work has taught them what "normal" looks like.
Veterinarians
May recognize unusual illnesses in pets or livestock that point to environmental hazards or emerging zoonotic diseases.
Wildlife biologists, park rangers, and game wardens
Notice unexpected animal deaths, migration changes, or unusual behavior that can signal diseases circulating in wildlife populations.
Farmers and livestock producers
Often observe clusters of illness, abortions, or unexplained deaths in animals before laboratory confirmation identifies the cause.
Water system operators and environmental technicians
Monitor subtle changes in water quality that may indicate microbial contamination or conditions favorable for disease.
Teachers and childcare staff
May be the first to recognize unusual patterns of absenteeism or similar illnesses spreading through a community.
Together, these professions form an extraordinary human observation network of people whose daily work places them where biology first begins to change.
What It Points To
Infectious disease surveillance often starts upstream from public health.
Outbreak Watch
Updates include active outbreaks and emerging signals I'm keeping an eye on. Information is verified through official public health agencies and credible reporting.
As of mid-morning, August 5th, 2026:
Active Outbreaks
EBOLA (Bundibugyo, DRC and Uganda)
The Bundibugyo Ebola outbreak in the Democratic Republic of the Congo continues to expand at an extraordinary pace. According to the DRC's SitRep#81 there have been 3874 confirmed cases and 1751 deaths, with transmission now active in 51 health zones in five provinces. Up from 48 health zones last week.
While response efforts continue under exceptionally difficult conditions, including insecurity, population displacement, healthcare worker shortages, and limited access to affected communities, the geographic expansion remains particularly concerning. Last week, I mentioned that I was watching whether transmission would establish itself in additional health zones. Unfortunately, that's exactly what has happened.
The encouraging news remains across the border in Uganda. After successfully interrupting transmission following repeated importations from the DRC, Uganda has not reported renewed spread, demonstrating once again that rapid case detection, contact tracing, and sustained public health response can prevent imported cases from becoming sustained outbreaks.
What I'm watching now is whether the pace of geographic expansion begins to slow. Case counts will continue to rise as long as transmission remains active, but the number of affected health zones provides an important measure of whether the outbreak is becoming more geographically entrenched or beginning to stabilize.
Since last week's update, confirmed cases have increased from 42 to 44 and the number of affected premises has increased from 32 to 34, while the outbreak remains confined to 15 Texas counties, and one New Mexico count.
The most significant operational development is related to sterile fly production. USDA recently revised the expected timeline for the new Texas sterile fly production facility to reach full operational capacity, shifting the projected date from late 2028 to 2029. That extends the period during which eradication efforts will rely on existing production capacity while the new facility is built and scaled.
But the most interesting development this week was conceptual. A new strategic assessment published today in Nature Ecology & Evolution reminds us that the US eliminated New World screwworm from North America, but maintaining that success always depended on sustained surveillance, sterile-fly production, technical expertise, and continued investment. Those systems, the authors argue, are part of eradication—not something that comes after it.
The paper also echoes a question I've mentioned several times in these updates: How much are we missing in wildlife? Because surveillance naturally focuses on livestock and companion animals, the authors suggest that wildlife infections may be substantially undercounted. (Absolutely 100%). That means the number of affected premises tells us about the outbreak's impact on agriculture, but not its full ecological footprint.
What I'm watching now is whether surveillance begins expanding beyond livestock. We won't get ahead of this or even catch up if we don't start finding and fighting it in the wild.
Cyclosporiasis (United States)
The country's largest recorded Cyclospora outbreak continues while investigators work to identify the contaminated food source. Michigan remains the epicenter, now reporting 12,218 confirmed cases. The CDC’s national dashboard remains behind state reporting and I still recommend using your state health departments for infomation in your area.
Traceback investigations are ongoing to identify the contaminated food source.
The epidemiologic evidence still points toward shredded iceberg lettuce supplied through a central Mexico growing region, but laboratory confirmation remains elusive. The voluntary recall remains in place while investigators continue working to strengthen the evidence linking illnesses to a common source.
Watching
Hantavirus (Chile)A very interesting signal this week is that Chile has declared its first nationwide health alert for hantavirus, remaining in effect through July 31, 2027. The alert covers 13 administrative regions, from Atacama to Magallanes (including Chilean Antarctica), encompassing the range of the long-tailed mouse that carries Andes hantavirus.
What makes this declaration especially noteworthy is its scope. The decree also expands preparedness for mosquito-borne arboviruses, including dengue and Zika, as well as avian influenza. It also grants health authorities additional powers to accelerate procurement of critical supplies, hire specialized personnel, strengthen epidemiologic surveillance, and coordinate response activities across affected regions.
Instead of waiting for multiple outbreaks to demand separate responses, Chile is using one recognized threat to strengthen the operational capacity needed to detect and respond to several. From a preparedness perspective, that's a strategically significant, and smart, move.
Important long-term signals:Though no major developments changed their trajectory this week.
Mpox (Clade I): I'm continuing to watch whether sustained transmission becomes established outside its historic endemic regions.
Oropouche virus: Expansion beyond the Amazon Basin remains the key long-term signal as changing vector distributions create opportunities for the virus to establish itself in new areas.
H5 avian influenza: My focus remains the same: not individual spillover events, but evidence of sustained mammal-to-mammal transmission or additional adaptations that would indicate a meaningful change in the virus's behavior.
Postscript
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One thing I didn't expect while researching this week's episode was how much I kept coming back to the wind.
I already love the wind but I hadn't fully appreciated how active a role it plays in shaping microbial life. Now I'm wondering what other infectious disease stories are hiding in moving air.
I've been sketching ideas for an immersive episode built entirely around the wind—not hurricanes or storms, but ordinary wind. I'm not sure what form it'll take yet, but I have a feeling there's an episode there somewhere.
On a completely different note, I've also heard good things about Cold Storage, the new film based on David Koepp's novel. Apparently it's equal parts science fiction, thriller, and creature feature, which sounds like exactly the sort of thing that belongs on an infectious disease podcast's weekend watch list. I'm hoping to watch it this weekend. If you have thoughts on it, let me know!
Until next week, here's a morning lake photo I took while camping with my son in Idaho a few years back.
— Heather
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