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Outbreak Watch: July 17, 2026

  • Writer: Heather McSharry, PhD
    Heather McSharry, PhD
  • Jul 16
  • 11 min read

Summary

Tonight’s outbreak update follows three epidemics currently unfolding: the expanding Bundibugyo Ebola outbreak in eastern DRC and Uganda, and screwworm and cyclospora in the US.

We also look beyond today's outbreaks to the signals I'm watching—including H5 avian influenza in mammals, the risk of severe Vibrio vulnificus infections as coastal waters warm, and how recent reductions in surveillance capacity may affect our ability to detect the next outbreak before it becomes a crisis.

Listen here or scroll down to read full episode.


Full Episode

Welcome to Outbreak Watch, where Infectious Dose gets you up to speed on the outbreaks unfolding now, the warning signs worth watching, and the questions people are asking.

Tonight we're covering the rapidly expanding Ebola outbreak in the Democratic Republic of the Congo, the New World screwworm response in the United States, and the growing cyclosporiasis outbreak that's now affecting dozens of states. Then we'll finish with two infectious disease signals I'm watching closely that haven't become outbreaks—but could become much more important in the months ahead.

Let’s begin in Central Africa.

Ebola in the Democratic Republic of the Congo and Uganda

The Ebola epidemic in the DRC has now surpassed 2,000 reported cases. The latest figures from the DRC's Ministry of Health, in their SitRep#62 published July 16, indicate 2,124 confirmed cases and 828 deaths. That means 38.9% of the people counted in the DRC outbreak have died. Of course that number can be affected by reporting accuracy among other things but either way it's a horrific regional outbreak afffecting five provinces in northeastern DRC, reaching 45 of their combined 140 health zones.

Cases also crossed the border into Uganda earlier in the outbreak but Uganda has not reported a new confirmed case in recent weeks and has now begun the formal countdown toward declaring its portion of the outbreak over. That's encouraging but the situation in the DRC remains profoundly serious.

The outbreak is also continuing to produce international exported cases. France confirmed it's first case in a doctor who had returned from a humanitarian mission in the DRC and was treated in a specialised hospital in Paris at the end of June. He has since recovered and been released. A second U.S. citizen was also diagnosed while doing humanitarian work in the DRC, and was medically evacuated to Germany and admitted to the University Hospital in Frankfurt on July 13. These cases do not indicate sustained transmission outside Central Africa, but they do highlight the ongoing risks faced by healthcare and humanitarian workers responding on the front lines.

That US citizens are not being brought home to be treated even though we have specialized facilities for it is also a red flag for US public health infrastructure right now.

For more info on this species of Ebola and it's transmission and pathogenesis, check out my episode, Containing Ebola.

New World Screwworm in the United States

Speaking of the US...New World screwworm remains one of the most closely watched agricultural outbreaks in North America. Latest reports indicate 39 cases in 13 TX counties and 1 NM county. While new detections continue to occur, the overall strategy remains unchanged. USDA and state partners are conducting surveillance, testing suspected infestations, treating affected animals, defining an infested zone, and releasing sterile flies. Southern ports of entry are currently closed to livestock trade, and animal movement restrictions are being used to reduce the possibility of carrying infestations into new areas.

Animal owners should check animals regularly, especially around wounds, surgical sites, bites, newborn navels, and areas that remain damp or irritated. And that includes those with pets who spend a lot of time outdoors, especially in affected counties. A screwworm infestation may appear as a wound that becomes larger rather than healing. There may be bloody drainage, a foul odor, visible larvae, restlessness, repeated licking or biting at the area, decreased appetite, or unusual isolation from the herd. Do not try to manage a suspicious infestation quietly at home. Prompt reporting helps protect the affected animal, but it also allows animal-health officials to determine whether more flies may be present in the area.

And although human infestations are rare, a wound with visible larvae—particularly after travel or animal exposure—requires medical evaluation.

I'm watching this outbreak for evidence of wild screwworm flies that were not recovered directly from an infested animal; cases outside the current geographic cluster; and signs that local reproduction is continuing despite sterile-fly releases. My longer-term concern is still wildlife. Livestock can be inspected and treated. Free-ranging wildlife cannot. And illegal movement of cattle and feral hogs can make the problem worse. If screwworm establishes a self-sustaining cycle outside managed animal populations, detection and eradication become substantially more difficult. A 2021 study on feral hogs in Uraguay and a recent study from the Wildlife Conservation Society on infestations in wildlife deep within remote forests in Central America, echo my concern.

For details on screwworm and how we eradicated it from the US...until we...didn't, check out my episode On the Fly.

The U.S. Cyclosporiasis Outbreak

The third outbreak for tonight is cyclosporiasis, affecting people across 34 states. As of recording, Michigan is the epicenter with 4,312 confirmed cases and 102 hospitalizations, making it by far the hardest-hit state in the country. Nationally, it's hard to say because the CDC is seriously behind in reporting. For comparison, only 249 cases had been reported nationally by approximately this point last year.

This year’s increase can't be dismissed as normal seasonal fluctuation. A little over a year

Screenshot of CDC FoodNet page on 7/16/2026, showing that of the 6 major foodborne pathogens, surveillance of all but 2, was changed from "done" to optional as of July 1, 2025. In case they hide this later.
Screenshot of CDC FoodNet page on 7/16/2026, showing that of the 6 major foodborne pathogens, surveillance of all but 2, was changed from "done" to optional as of July 1, 2025. In case they hide this later.

ago, CDC's FoodNet program actively tracked Cyclospora through participating sites, providing more timely national surveillance. Following cuts to FoodNet surveillance on July 1, 2025, and reductions in public health staffing, federal detection and response efforts are crippled. As I record this episode, state health departments have collectively reported nearly 7,000 confirmed cases, while CDC's published national confirmed count remains substantially lower and acknowledges thousands of additional reports awaiting processing. The national picture is incapable of keeping pace with the states.

What is Cyclospora?

Cyclospora cayetanensis is a microscopic parasite that infects the intestinal tract. People become infected by swallowing food or water contaminated with the parasite. In the US, outbreaks are frequently associated with fresh produce that had been irrigated with sewage-contaminated water. Previous investigations have implicated foods such as leafy greens, herbs, berries, snow peas, green onions, and prepackaged salad mixtures.

The most common symptom is frequent watery diarrhea. People may also experience loss of appetite, weight loss, abdominal cramping, bloating, nausea, profound fatigue, and sometimes fever or vomiting. Symptoms usually begin about one week after exposure, although the incubation period can range from approximately two days to two weeks. Without treatment, the illness can improve and then return repeatedly for weeks or longer.

Do we know what food is responsible?

We don't have confirmation but in Michigan, preliminary evidence suggests that leafy lettuce, especially in prepackaged salad mixes, is the culprit, likely from Taylor farms who supplies not only taco bell but many fast food places and other companies. Whether we have one supplier spreading infectious lettuce around the country or multiple separate outbreaks, is currently not known. If only we had an organization with experts in epidemiology and infectious diseases to sort this kind of thing out.

Should people stop eating fresh produce?

Look, pre-washed doesn't mean sterile. Washing fruits and vegetables under running water can remove dirt and reduce some contamination, but it cannot guarantee the removal of Cyclospora. Taco Bell knows this and is actually leading the charge by deciding to not use fresh lettuce, cilantro, and guacamole in their foods until this is sorted. So don't try washing produce with soap, detergent, bleach, or disinfectant. While it's easily treatable it can cause post-infectious IBS that lasts months, so follow Taco Bell's lead and just avoid it if you can.

Can it spread from one person to another?

The parasite shed in human stool is not immediately infectious. It must mature in the environment before it can infect another person so an infected food worker is not likely to contaminate a meal and immediately transmit Cyclospora in the same way that norovirus can spread. In other words, direct person-to-person transmission is unlikely.

But human fecal contamination somewhere in the food or water production chain is ultimately how the parasite enters that chain.

When should someone contact a healthcare provider?

Prolonged or relapsing explosive, watery diarrhea—especially during spring and summer —deserves medical attention. Cyclospora is easy to miss because standard stool testing may not automatically include it. A healthcare provider may need to order a specific molecular or microscopic test. It's worth saying to your clinician: “I have had persistent watery diarrhea. Could this be Cyclospora, and has the correct test been ordered to find out?”

What non-outbreak infectious disease signals am I keeping my eye on?

1) H5 avian influenza in mammals

While human infections remain uncommon, H5 avian influenza viruses continue reshaping the wildlife landscape in ways that are difficult to ignore. Norway reported the first detection of H5N5 avian influenza in a polar bear in Europe in May, and we've seen spillover of H5N1 into elephant seals again....in California with a limited outbreak in the spring of this year and more recently on Australia's remote Heard Island there was catastrophic mortality from H5N1 in southern elephant seal pups...an estimated 13,000 deaths. Although these are different influenza subtypes, both belong to the broader H5 lineage and illustrate the same pattern: highly pathogenic avian influenza viruses continue crossing into new mammalian hosts.

Every successful mammalian infection gives these viruses another opportunity to adapt to a mammalian host. That's why I'm watching these spillover events more closely than the relatively small number of human cases.

One study published in May also caught my attention because it may help explain how H5N1 spreads through dairy farms. Researchers detected viral RNA in the breath of infected cows, recovered infectious virus from air samples collected inside milking parlors, and found widespread contamination of wastewater and milk before some cows showed obvious signs of illness. This doesn't prove cows are efficiently infecting one another simply by breathing, but it does suggest the virus may have more opportunities to move through dairy environments than we previously appreciated.

Other signals that would also concern me include unexplained clusters of illness in people without animal exposure, evidence of person-to-person transmission, increasing severe disease among exposed workers, or genetic changes associated with adaptation to mammals. In addition to paying close attention to what we're learning about transmission within dairy cattle, I'm watching for infections in other species that live closely with people—especially pigs and cats. Pigs deserve special attention because they can be infected by both human and avian influenza viruses, creating opportunities for reassortment. Cats are susceptible to severe disease—including neurological illness—and can become infected through contact with sick birds or contaminated raw animal products.

For now, the guidance hasn't changed. Avoid contact with sick or dead wild animals, don't feed pets (or yourself) raw milk or raw poultry products, keep cats away from sick birds, use appropriate protective equipment if you work around infected animals, and seek medical advice if you become ill after a potential exposure.

I have an episode on avian flu if you'd like more info on that.

Vibrio vulnificus

The second signal I am watching is Vibrio vulnificus. Vibrio bacteria occur naturally in coastal and brackish waters. As water temperatures rise, conditions become more favorable for their growth and geographic expansion. People can become infected by eating contaminated raw or undercooked seafood—especially oysters—or when an open wound is exposed to coastal water or prepping seafood. Most people will not develop a devastating infection. But in someone with liver disease, iron-overload disorders, diabetes, immune compromise, or other underlying conditions, Vibrio vulnificus can invade the bloodstream and become life-threatening very quickly.

Wound infections can also progress rapidly, destroying tissue and sometimes requiring intensive care, surgery, or amputation. This is not a reason to panic every time someone goes to the beach but you should be aware of the risk.

So avoid warm coastal or brackish water when you have an open wound, recent surgical incision, piercing, or tattoo. Waterproof bandages help, but avoiding exposure altogether is safer when a wound cannot be 100% protected. And wear gloves when handling raw seafood. And don't eat raw oysters if you have liver disease or another condition that places you at high risk.

If you experience rapidly increasing pain, swelling, redness, blistering, fever, or skin discoloration after coastal-water or seafood exposure. Do not wait to see whether it improves overnight. Seriously. Vibrio is one of the pathogens for which FoodNet reporting became optional in 2025 and it escalates to deadly in hours. For more detail Check out my episode, No Boat Big Enough.

Now, other surveillance systems still exist, but reduced active surveillance means I am particularly alert for local reports as I have no doubt that paying attention to local clusters is how an outbreak will be identified when we have such limited surveillance and response capabilities.

Until next week, stay healthy, stay informed, and spread knowledge not diseases.









ANNOTATED CITATIONS AND RESOURCES

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