(RNN) – The Fourth of July holiday often means lots of beach time.
Hot summer days and cool water are a perfect match.
But the Centers for Disease Control and Prevention reminds beachgoers that there are some hidden dangers in the water that can make you sick.
In a 10-year study from 2004 to 2014, researchers analyzed 140 disease outbreaks that sickened at least 4,958 people from 35 states. Two of the people died.
The CDC found that untreated warm freshwater at beaches and public parks with lakes, reservoirs and ponds posed the greatest risk of sickness for swimmers.
Fecal contamination of the water from human or animal waste was the biggest threat, which can cause a number of noroviruses, including E. coli.
All of the noroviruses can cause stomach pain, nausea, diarrhea and vomiting.
The disease infects people when water containing the amoeba enters the body through the nose and travels to the brain and destroys tissue.
To avoid exposure to the amoeba, use a nose clip when swimming.
The CDC also offers some more general advice for staying safe when swimming this summer. Stay out of the water if:
- The beach is closed or an advisory is posted for high bacterial levels or other conditions, such as sewage spills or harmful algal blooms.
- A recent heavy rain has occurred.
- A discharge pipe can be seen on the beach.
- Fish or other animals in or near the water are dead.
- Water is discolored, smelly, foamy or scummy.