A mysterious stomach bug has sickened more than 275 in eight states, and the Centers for Disease Control and Prevention is struggling to find the cause.

The bug itself is an intestinal parasite called cyclospora, typically found in tropical countries in Latin America. But the source of the recent infections in the United States is unknown, though the most likely cause is contaminated water or food.

Cyclospora infection presents as typical food poisoning. Victims suffer from an upset stomach or diarrhea days or weeks after exposure, but other symptoms can result from cyclospora.

According to the Mayo Clinic, these can include:

- Watery diarrhea
- Frequent and sometimes explosive bowel movements
- Bouts of diarrhea alternating with bouts of constipation
- Loss of appetite
- Weight loss
- Bloating
- Flatulence
- Burping
- Stomach cramps
- Nausea
- Vomiting
- Muscle aches
- Low-grade fever
- Fatigue
- General feeling of unwellness (malaise)

The diarrhea and pain may subside on their own after a few days, as the body flushes out the parasite, but young children, the elderly, and patients with compromised immune systems, such as people with HIV should see a doctor, as should anyone whose symptoms last longer than a few days.

The exact mode of transmission for cyclospora is unknown, but it isn't contagious, so family members won't spread it among themselves. However, an entire family could have been exposed via the same method, such as shared food or water.

Diarrhea can cause dehydration, so drink plenty of water. Children can be given a rehydration solution, such as Pedialyte. Avoid anti-diarrheal medication, since it can prevent the body from flushing out the parasite. Avoid diuretics, like alcohol or caffeine in coffee, tea and soft drinks.

The most common treatment for cyclospora is antibiotics, which must be prescribed by a doctor. Typically, trimethoprim-sulfamethoxazole is used, which is sold under the brand name Bactrin or Septra. Cipro (ciprofloxacin) or Alinia (nitazoxanide) may also work.