If you're going to wade into the Virgin River at Zion National Park, it's recommended that you don't submerge yourself or drink from the river/NPS file

Issues with cyanobacteria in sections of the Virgin River continue to be a problem at Zion National Park in southwestern Utah. Though the bacteria is a natural part of aquatic environments, some varieties might produce dangerous liver and nervous system toxins, according to park staff.

Problems with the bacteria surfaced last summer when a dog that was playing in the North Fork of the river upstream of the national park died soon after swimming in the water. 

Water samples taken at the time showed anatoxin-a concentration greater than 55 micrograms per liter in some samples. The health threshold for primary recreation from the Utah Department of Health and Department of Water Quality is 15 micrograms per liter. Additionally, harmful cyanobacteria that produce anatoxin-a were identified in multiple areas of the North Fork of the Virgin River, the park said at the time.

Health advisories for algal blooms in the North Fork of the Virgin River remain in place. Utah environmental quality officials say a heavy, flushing rain is needed to clear out the blooms. However, the forecast does not call for such storms in the near future.

For the foreseeable future, park visitors should not submerge themselves in the Virgin River or drink the water.