Everything you need to know about the McDonald's salad parasite outbreak

As of July 26, the Centers for Disease Control and Prevention (CDC) reports a total of 286 people in 15 states have been infected with a parasite called Cyclospora, an increase of 120 people in the last week alone.

So far, there have been 11 hospitalizations but no deaths associated with this outbreak. The parasite has been linked to salads from McDonald’s.

So what is this parasite, and why are the numbers still increasing?

What is Cyclospora?

Cyclospora is a parasite found in contaminated food or water -- which in the U.S. can mean fresh produce -- and causes a short-term illness known as Cyclosporiasis.

The parasite isn’t typically transmitted from one person to another, but rather, makes people sick after it is ingested.

What are the signs of an infection?

Once someone ingests food or water contaminated with Cyclospora, symptoms of the infection may not begin until about a week later, sometimes even up to two weeks.

The symptoms include copious, sometimes explosive, watery diarrhea, low-grade fever, cramping or bloating with increased gas, nausea, and tiredness. These symptoms can last anywhere from one to several weeks. Without treatment, symptoms can come and go for several months.

Why is the number of people infected increasing?

McDonald’s voluntarily recalled salads from over 3000 restaurants in 14 states on July 13.

The people who ate those salads before July 13th may just be starting to develop symptoms -- prompting them to seek medical attention. Therefore, the official number of people infected by this parasite may continue to increase in the next few weeks as more reports come in.

What should people do if they have symptoms that may indicate Cyclosporiasis?

If people have eaten at a McDonald’s restaurant in the affected states recently and develop diarrhea, they should see a healthcare provider to discuss whether testing for Cyclospora is warranted.

If the infection is confirmed, it is typically treated with a course of antibiotics and rehydration as needed.

Signs of severe dehydration that require immediate medical attention include: increasing sleepiness, dizziness or confusion, fainting, or chest pains.

Dying from cyclosporiasis is rare in healthy adults. Children and those with impaired immune systems are at increased risk for complications.

Dr. Stephanie Sophie Lee is a pediatrician and preventive medicine resident in South Carolina and a resident in the ABC News Medical Unit.