A “large and growing” outbreak of a parasitic infection is spreading in Michigan, health officials warned this week.

As of Thursday, more than 300 cases of cyclosporiasis, an intestinal infection, have been confirmed, the Michigan Department of Health and Human Services (MDHHS) told ABC News. Typically, the state only sees about 50 cases per year, according to MDHHS.

The parasite usually spreads through food or water contaminated with feces, according to the Centers for Disease Control and Prevention (CDC).

“We are working closely with our state and local partners to identify the source of this outbreak that is making so many people ill as quickly as possible,” Lynn Sutfin, public information officer for MDHHS, told ABC News.

The outbreak comes as the CDC reports 145 cases have been infected in 17 states, excluding Michigan, as of June 15, with at least 20 people hospitalized.

Residents in Pennsylvania and New Jersey are among those dealing with the illness.

Authorities are investigating several clusters of cyclosporiasis cases in multiple states.

Doctors told ABC News that cases usually start in May, so the Michigan outbreak occurred during the time or year when public health specialists typically would see a rise in cases. However, the number of cases in Michigan is particularly high, doctors said.

Dr. Peter Chin-Hong, an infectious diseases specialist and associate dean for regional campuses at the University of California, San Francisco, told ABC News that in years past, the U.S. used to see many cases cyclosporiasis acquired outside of the U.S, or from imported vegetables and fruits.

“But now we’re starting to have more domestic cases as well,” Chin-Hong said.

Foodborne outbreaks of cyclosporiasis have been linked to various types of imported fresh produce, such as raspberries, basil, snow peas, mesclun lettuce and cilantro, according to the CDC. The agency further said it takes about one week from the time of infection to become symptomatic, but that time can range from two days to two weeks.

Some patients do not experience any symptoms but, for those who do, the most common symptom is “explosive watery diarrhea,” Dr. Zoe Weiss, director of clinical microbiology at Tufts Medical Center, told ABC News.

Other symptoms can include cramping, bloating, low-grade fever, nausea and vomiting, Weiss said.

“Though in most cases this illness causes discomfort from cramping, bloating and watery diarrhea, we are concerned about individuals who may be immunocompromised due to cancer treatment or an organ transplant as the effects may be more severe,” Sutfin from MDHHS said.

Weiss said the infection is very unlikely to spread from person-to-person “because the parasite is passed in the stool, and then it requires days to weeks of sporulation in the environment before it can become infectious.”

Chin-Hong said that oftentimes people dismiss watery diarrhea, but it is important to get a diagnosis to get treatment as soon as possible.

Cyclosporiasis is treated with the oral antibiotic trimethoprim-sulfamethoxazole (TMP-SMX), commonly sold as Bactrim, Septra and Cotrim, taken for 10 days, according to the CDC.

Doctors told ABC News that people can prevent infection by thoroughly washing produce, cutting away bruised or damaged parts of fruits and vegetables, and refrigerating pre-prepared or pre-cut produce.

“If you’re in an area that’s been affected and you have sudden ongoing watery diarrhea, you should definitely seek a physician and get treatment,” Weiss said.

Flags are flying at half-staff across Pennsylvania today after Gov. Josh Shapiro ordered them lowered statewide to honor Pennsylvania State Trooper Michael Pahira, who died in the line of duty in Schuylkill County.

Shapiro ordered flags fly half-staff at Pennsylvania facilities, public buildings and grounds — the United States flag and Pennsylvania flag — to honor Pennsylvania State Trooper Michael Pahira, who died in the line of duty in Schuylkill County.

Pahira died after being struck by a tractor-trailer while conducting a commercial vehicle inspection along Interstate 81 in Schuylkill County, authorities said. A Massachusetts truck driver has since been charged in the crash, and flags will remain at half-staff until the date of Pahira’s interment, which has not yet been announced.

Why are flags at half-staff today in Pennsylvania?

Gov. Josh Shapiro ordered flags across Pennsylvania to fly at half-staff in honor of Pennsylvania State Trooper Michael Pahira, who died in the line of duty July 1. The order applies to Commonwealth facilities, public buildings and grounds statewide and remains in effect until his interment.

What’s the difference between half-staff and half-mast?

The difference between a flag flying at half-staff and half-mast depends on where the flag is flown. In the United States, flags on land are lowered on staffs, while half-mast traditionally refers to flags flown from ships and at naval stations ashore.

Who was Trooper Michael Pahira?

Pahira was a Schuylkill County native and nearly 20-year veteran of the Pennsylvania State Police, authorities said. He enlisted in January 2007 and was assigned to Troop L in Frackville as a Motor Carrier Inspector. He was 44 years old and became the 106th member of the Pennsylvania State Police to die in the line of duty.

What happened to Trooper Michael Pahira?

State police said Pahira was conducting a commercial vehicle inspection along Interstate 81 southbound in Schuylkill County when a second tractor-trailer left the roadway and struck his marked patrol vehicle and the truck he was inspecting before hitting him. Both commercial vehicles caught fire after the crash. Pahira was taken to a hospital, where he was pronounced dead. Authorities said a Massachusetts truck driver has since been charged with homicide by vehicle in connection with the crash.

How long will flags be lowered?

Pennsylvania Gov. Josh Shapiro ordered US and Pennsylvania flags fly half-staff today and through the date of interment, or the burial or entombment of Pahira following his funeral.

Lori Comstock is a New Jersey-based reporter covering trending news with USA TODAY Network’s Mid-Atlantic Connect Team. She covers news in the Northeast, including New Jersey, Pennsylvania, Delaware, Washington DC, Maryland, and Virginia. Reach her at LComstock@usatodayco.com.