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.

“This is the most patriotic town in the United States,” Little said. “We always take it as seriously as if it was USA 250.”

The town’s “patriotic exercises,” first led by the Reverend Henry Wight on July 4, 1785, are what allows it to lay claim as the oldest continuous celebration of the nation’s independence. (The parade itself has been canceled a handful of times, most recently in 1881 when President Garfield was shot on July 2.)

Serious parade-goers stake out their spots the night before and stay put, but the official rules say you cannot put out a blanket or chair until 5 a.m. on parade day.

More than 30 floats will be in this year’s procession, which is officially called the Military, Civic and Firemen’s Parade. Electoral politics are banned; candidates for office are not allowed to march, though certain current office-holders are allowed in. (The rule once drew the ire of the late Buddy Cianci, a former Providence mayor who was barred from the parade while running for governor in 1980 and showed up anyway, arriving by helicopter.)

“If you’re in Bristol, you’re not a Democrat, you’re not a Republican on this day,” Little said. “We really and truly are united in that we are thankful for our freedoms.”

The planning for the parade, now in its 241st year, takes place year-round; the committee starts meeting in August to plan next year. It costs $250,000 to throw the celebration, which is entirely funded by donations, Little said. There are more than 100 volunteers.

Fireworks are set for July 3 at 9:30 p.m. over Bristol harbor. Patriotic exercises will take place at 8:30 a.m. on July 4 at Colt Memorial School, followed by the parade at 10:30, which steps off from the corner of Hope and Chestnut streets.

Near the end of the parade route, where workers were setting up a stage Wednesday, visitors came from around New England to get a glimpse of a Rhode Island copy of the Declaration of Independence printed in 1777.

The broadside of the document was printed on stiff parchment and yellowed with age. The sheet was guarded by local police and a Rhode Island State Patrolman, and set behind a glass frame.

The first Congress-authorized copies of the Declaration with the names of the signers were printed by Connecticut native and printer Mary Katherine Goddard, who ran a print shop in Baltimore. Goddard “risked her life and livelihood” by including her name on the copies, according to the Bristol Historical and Preservation Society.

Seeing Goddard’s name on the document was an “emotional experience” for Sara Sooknah of Bristol because Goddard was so involved, Sooknah said.

On some of Goddard’s prints, her name has been crossed out.

“I was so happy to see a woman was involved at that time with the development of our country,” she said. It was just a beautiful thing to see. It was emotional to see this actual document.”

Sooknah said she and her partner, Raj, who was born on the Fourth of July, weren’t initially aware it was an American holiday until they moved to the US from England, said they have traveled the world and been to places “you wish had freedom,” particularly for women. The couple met in Saudi Arabia.

“We’re just going to continue to be grateful for what we have in this country every day,” Sooknah said. “Because we both traveled around the world, we get to see how much we have to be grateful for in this country.”

Janet Clancy of Barrington, who also viewed the Declaration of Independence at the John Post Reynolds School in Bristol — now the Reynolds Art & Wellness Center — said she is planning to watch the parade on July 4 and the fireworks afterward. Clancy said she was raised on the West Coast and the Fourth always included backyard picnics and fireworks.

Since she has lived in Rhode Island, her Independence Day tradition has always been going to the Bristol parade and parties.

“I was 12 during the bicentennial,” said Clancy, who has all of the quarters the US Mint issued to commemorate the occasion. “When they bring in the tall ships here, or even in Boston, we don’t have that on the West Coast. I think that brings you back 250 years.”

Catherine Zipf, executive director of the Bristol Historical and Preservation Society, said the 250th anniversary brings an opportunity to return to America’s roots at an opportune moment.

“We really need to remember why we did want to separate from Britain, why we did declare our independence, what it was about our founding principles that we wanted to be equal, that we wanted to be pursuing life, liberty, and the pursuit of happiness, and all of that,” Zipf said. This is a good moment to be reminded of the founding principles and that we have some work to do.”

Constitutional rights under intense debate include immigration, due process, reproductive rights, freedom of speech and assembly, separation of powers, birthright citizenship, and more.

“To me, the principles of the Constitution are holding up,” Zipf said. “It’s holding its own nicely against some pretty significant attacks and I think in the end it seems to me that we’re coming around to that the principles were correct in the first place.”

Zipf said that having the opportunity to show people American history through the lens of living history reenactors and unique documents like real copies of the Declaration of Independence, helps to reinforce the values the US was built on.

“I feel strongly that looking at original documents matters, that the authenticity of the object that we’re looking at is really important,” she said. “I think people feel differently when they get to see the original, as opposed to a picture on the internet. There’s a palpable quality … it makes an impact on people.”

Carlos Muñoz can be reached at carlos.munoz@globe.com. Follow him @ReadCarlos and on Instagram @Carlosbrknews. Steph Machado can be reached at steph.machado@globe.com. Follow her @StephMachado.

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