Clear skies and warm waters may tempt many to head to the beach this holiday weekend, but officials are warning millions of July 4 vacationers to think twice before entering the water because they could be infected with a deadly bacteria.

States and local counties have been posting advisories all week about closures and more are still being added to the list.  

At least 100 beaches across 12 states are now closed or under advisories across the country because of bacterial blooms.

Affecting both fresh and saltwater beaches, the warnings have mostly been triggered by E. coli — which can infect people if they swallow contaminated water and usually cause abdominal cramps and diarrhea.

But officials warn deadly micro-organisms are likely also multiplying in the water, including Vibrio vulnificus — a flesh-eating bacteria that can infect open wounds and kills one in five patients.

The pathogen Naegleria fowleri also lives in freshwater and can infect people if water enters their body through openings. The micro-organism attacks the brain and is nearly always fatal, killing about 97 percent of patients.

Beaches shuttered by warnings include two popular spots on the city of Chicago’s northern lakefront and three beaches on the coastline near New Jersey’s famed Sandy Hook beach.

It isn’t clear why bacteria populations are surging this time of year, but it may be linked to recent heavy rainfall in parts of the country.

This can wash a surge of extra nutrients into waterways, which can then cause bacterial blooms as microorganisms use up the resources.

In a notice posted in Suffolk County, New York, officials warned that ‘bathing in bacteria-contaminated water can result in gastrointestinal illness, as well as infections of the eyes, ears, nose and throat’.

Officials in Massachusetts, the state that has closed the most beaches in the US, warn that it has closed beaches due to ‘bacterial exceedance’ — or blooms in bacteria.

DailyMail.com pored over local news reports and state health department websites covering the more than 5,000 beaches in the US.

The states with beach closures or advisories are: California, Illinois, Massachusetts, Michigan, Missouri, New Hampshire, New Jersey, New York, Oregon, Vermont, Washington, Wisconsin.

Overall, Massachusetts had the most beaches closed or under advisories at 26, both freshwater and saltwater, in total.

Illinois had the second highest number at 24 beaches, according to its state dashboard.

And Vermont had the third highest, at 19 beaches, according to local media reports.

Wisconsin was the only other state with more than 10 beaches closed, with a total of 14 closures or advisories reported by local media.

At least a hundred beaches across 12 states are closed or under advisories across the country because of bacterial blooms

Advisories are triggered if E.coli levels in water exceed 235 colonies per 100 milliliters.

About 265,000 people are sickened with E. coli every year, reports suggest, although these are normally linked to contaminated food.

Early warning signs of an infection include abdominal cramps, diarrhea which may be bloody and nausea and vomiting.

In serious cases, these can become severe and patients can become dehydrated, suffering from dizziness and decreased urination.

The infections are more risky in old people, who have a weaker immune system, and young children, with about 100 people dying from E. coli in the US every year.

When E. coli is present in water, however, experts say it is likely that other more dangerous micro-organisms are also multiplying in the water, including Naegleria fowleri and Vibrio vulnificus

Only around five people have ever survived a Naegleria fowleri infection in the US, statistics suggest, out of about 164 infections. 

Among them is Maryland local Ryan Perry contracted Naegleria fowleri in May 2019 after using a jet ski on the Susquehanna River. 

Ryan Perry was hospitalized after contracting Naegleria fowleri. He is pictured above in the hospital

He noticed the water seemed opaque with sediment, but carried on — spending three hours whipping around the reservoir.

The next day, he had the worst headache he had ever experienced, he said, prompting him to go to the doctor a day later when it persisted — leading him to be sent to the emergency department, where the amoeba was diagnosed.

He remained on a ventilator for more than two weeks before recovering, but he also had to relearn basic movements again — in a process that took more than two months.

In a case involving Vibrio vulnificus, a woman had to have her leg amputated after she caught the bacteria while swimming.

Vibrio infects people by entering the body through cuts and abrasions, and then starts to eat away at the flesh, often causing serious complications. 

Debbie King, 72 and from Florida, suffered from a cut while climbing onto her friend’s boat in the Gulf of Mexico in August 2023.

She initially thought nothing of the abrasion, and dismissed the red and sore shin she suffered the next day as due to sunburn.

But after the area became red and blistered three days later, she went to her doctor — who immediately referred her to the emergency department.

There, doctors said that she had been infected with the Vibrio bacteria and could die if they did not amputate her leg.

According to the CDC, about 150 to 200 cases of Vibrio are reported annually, with 20 percent resulting in death.