An explosive stomach infection is hitting the US, how the Cyclospora parasite is making people unwell and what researchers know so far about its source.

The United States is currently battling a growing Cyclospora outbreak across the states. According to researchers, this is the largest outbreak of its kind in the country’s history, and health officials have not yet identified its source.

Since May 1, 1,645 cases of the parasite have been confirmed in 45 states, and more than 5,100 more cases are under investigation.According to Joel Barratt, a molecular parasitologist at Emory School of Medicine in Atlanta, Georgia, these numbers quickly exceeded the total number of cases that typically appear within a year. More than 100 people with parasitic infections were hospitalized, but no deaths were reported.

What is Cyclospora and how does it affect people?

Cyclospora cayetanensis is an intracellular parasite, meaning it invades and then hijacks the host’s cells, especially those in the lining of the intestine, according to Nature. Once inside, it begins to multiply rapidly, damaging cells. It may take a week or more for the parasite to complete its life cycle and cause enough damage for symptoms to appear.Being infected means that someone has consumed food or water contaminated with human feces.

Cyclospora cayetanensis reproduces through egg-like structures called oocysts that are shed in human feces. These eggs are not immediately infectious: they must first reproduce, or mature, in a warm environment at temperatures between 22°C and 32°C for a week or two, which is one reason why outbreaks occur during the summer.The main symptom is watery diarrhea because the parasite inflames the intestinal lining and disrupts the body’s ability to absorb water and nutrients, causing excess fluid to be expelled through the intestines.

While the infection runs its course as the immune system expels the parasite from the body, the illness can last for weeks or even months.The main treatment doctors use to fight the parasite is the combination antibiotic trimethoprim-sulfamethoxazole (sold as Bactrim). Antibiotics are not typically used against parasites, but the bacteria deprive Cyclospora of an essential vitamin it needs to reproduce.

How are researchers trying to determine the origin of the outbreak?

Health officials are still working to determine the source, but the state of Michigan, which reported the largest number of infections, 4,300, indicated that lettuce or salad greens may be to blame.

On Thursday, the U.S. Food and Drug Administration identified shredded iceberg lettuce from a supplier in Mexico that was sent to Taco Bell locations in five states as one of the sources of the outbreak, but other food sources are likely driving the spread.Tracking the parasite requires coordination between U.S. health officials and federal health officials. First, state laboratories collect stool samples from people with symptoms of the disease and send them to federal facilities.

If a sample tests positive for Cyclospora, health officials will ascertain when the person started showing symptoms and record what the person ate in the previous weeks.

How to prevent infection?

The best way to prevent illness is to follow standard hygiene and food safety practices. It is important to wash hands with soap and water after using the bathroom and before and after preparing food, as alcohol-based hand sanitizers do not kill Cyclospora; However, soap and water do.

Cleaning produce with vinegar was more effective than simply using running water alone. The product is safest when heated to 158°F or higher, which kills Cyclospora.

Foods to avoid during Cyclospora infection

Because Cyclospora embeds itself into the texture of delicate, moist, leaf surfaces, previous outbreaks have been linked to:

According to the Centers for Disease Control and Prevention, the typical Cyclospora season lasts until late August, and cases can continue to rise until then.