Summer Stomach Bugs in Maryland: Food Poisoning, Cyclospora, and When to See a Doctor

Every summer our Rockville, Gaithersburg, and Columbia offices see a wave of patients with the same story: cramping, watery diarrhea, low energy, and a stomach that will not settle. Warm weather is prime time for foodborne illness. Bacteria multiply quickly in food left out at cookouts, and summer produce shipments occasionally carry a less familiar culprit called cyclospora.

Why stomach bugs spike in summer

Most summer gastrointestinal illness comes from food handling: meats undercooked on the grill, salads and dairy sitting in the heat, and cross-contamination between raw meat and ready-to-eat food. The common bacterial causes are Salmonella, Campylobacter, and certain strains of E. coli. Norovirus, the classic cruise-ship and potluck virus, circulates year-round. Most Maryland cases occur in the spring and summer months, specifically May through August.

Most of these run their course in one to three days with rest and fluids. The illness that behaves differently, and the one we want you to know about this summer, is cyclospora. Warm weather is excellent for the multiplication of the immature parasite (oocysts), which is why we see these outbreaks in the summer months.

What is cyclospora?

Cyclospora is a microscopic parasite most often linked to imported fresh produce such as herbs, lettuces, and berries. It is generally not spread person to person.

Cyclospora infection is a foodborne and waterborne parasitic cause of diarrheal illness in children and adults, and humans are the only natural hosts. The risk factors include contaminated water, food, or soil, and poor sanitation. In nonendemic regions like the United States, and here in Maryland, most cases are imported by international travelers or come from eating contaminated food, so US outbreaks are often linked to produce from endemic countries: raspberries, lettuce, cilantro, prepackaged salad mix, snow peas, mango, carrots, and other vegetables. This time, the source has been investigated and traced to lettuce.

The average incubation period is about seven days between swallowing the parasite and the start of symptoms, though it can range anywhere from 2 to more than 14 days. The telltale signs are loss of appetite, nausea, gas, fatigue, belly cramping, and above all watery diarrhea. You may run a low-grade fever, and weight loss is common. In a few cases the diarrhea comes on abruptly and contains mucus or blood.

Two things make cyclospora worth a doctor visit. First, a routine stool test can miss it; the lab has to look for it specifically, so telling us about prolonged watery diarrhea matters. Second, unlike most stomach bugs, it has a specific treatment: a course of the antibiotic trimethoprim-sulfamethoxazole (Bactrim), usually 10 days to 2 weeks, typically clears it, while untreated symptoms can drag on and relapse for a month or more. That is why we recommend a prompt visit to your primary care doctor, to avoid the longer-term consequences of this infection. For patients with a sulfa allergy, the alternative is nitazoxanide.

What you can do at home

• Prioritize fluids. Water, broth, and oral rehydration solutions containing a pinch of salt and sugar are better than sports drinks. Small, frequent sips stay down better than large amounts. We can prescribe Zofran to control nausea.
• Eat bland and light as tolerated. There is no need to force food in the first day or two.
• Be careful with anti-diarrheal medicine. Do not take loperamide (Imodium) if you have a high fever or blood in the stool, and ask us first if you are unsure. Loperamide can keep the parasite from clearing in your stool, letting it stay longer and working against your body’s own mechanism for getting rid of it.
• Prevent the next round: wash produce thoroughly, keep raw meat separate, cook to safe temperatures, and refrigerate leftovers within two hours (one hour above 90°F). Prevention is always better, and healthy habits prevent unwanted doctor visits.

When to see a doctor

Visit us at the clinic, or book a telehealth visit, if any of the following apply:

• Diarrhea lasting more than 3 days, or any watery diarrhea lasting more than a week (this is the cyclospora pattern)
• Fever of 102°F or higher
• Blood or black color in the stool, which can signal a more extensive infection
• Signs of dehydration: very dark urine, dizziness on standing, dry mouth, decreased urine production
• Repeated vomiting that makes it hard to keep fluids down
• You are pregnant, over 65, or have a weakened immune system or a serious chronic illness such as diabetes or kidney failure, or you take immunosuppressive medications such as Humira, Skyrizi, or steroids

Go to the emergency room or call 911 for severe or constant abdominal pain, confusion, fainting, or a complete inability to keep any fluids down.

How we can help

We offer same-day sick visits at all three Maryland offices and telehealth visits from home, which are ideal when you would rather not leave the bathroom far behind. We can order the right stool testing, treat cyclospora and other infections when found, and manage rehydration before it becomes an emergency. Book an appointment online or call (301) 762-7723.