It's safe to go back into the water.

The Virginia Department of Health has lifted a recreational advisory, the result of a harmful algae bloom on the North Fork of the Shenandoah River in Shenandoah and Warren counties from Chapman’s Landing to Riverton, the health department announced in a news release Friday.

This river segment (approximately 52.5 miles) was placed under a recreational advisory on Aug. 10 due to widespread algal mats, which contained both cyanobacteria cells and toxins at elevated levels.

Weekly observations at numerous sites along the river indicate that these mats are no longer visible.

Water samples collected Sept. 14 show that no cyanobacteria cells are present and toxins are at or below detection limits, well below those that pose a human health risk.

It is still possible for algal blooms to reappear when there is adequate sunlight, nutrients and warmer temperatures to make conditions favorable for algal growth, the health department advises.

Most algae are harmless. However, some may produce irritating compounds or toxins if ingested. Because it is difficult to tell the difference, VDH advises everyone to avoid discolored water, scums or mat material that are green or bluish-green because they are more likely to contain toxins.

The algae blooms, which occurred in this area, may produce mats along the river bottom that may then detach, float on the water surface, or accumulate along downstream shorelines.

The North Fork of the Shenandoah River serves as the drinking water source for Strasburg, Woodstock, and Winchester. All three localities took every precaution to prevent impacts to drinking water, including routine testing for cyanotoxins and optimization of treatment processes for cyanotoxin removal.

Anatoxin-a, the main toxin present in this harmful algae bloom, has not been detected in Strasburg's raw (untreated) or finished drinking water since Aug. 12, and toxin levels remained below VDH and Environmental Protection Agency health advisory levels at all times during this event.

Anatoxin-a was below detectable levels in Woodstock's and Winchester's raw and finished drinking water for the duration of the harmful algae bloom. Drinking water remains safe to drink and use in all three localities.

Harmful algae can cause skin rash and gastrointestinal illnesses, such as upset stomach, nausea, vomiting and diarrhea. Some toxins in algae blooms can be fatal to dogs and other animals when ingested. If you or your animals experience any negative health effects after swimming in or near an algal bloom, seek medical or veterinary care promptly, the news release said.

Whenever recreating in natural waterbodies follow these healthy water habits:

• Avoid contact with any area of the river if you observe algae or algal mats to be present.

• Humans and pets should never consume water or material from a natural waterbody because this water is not treated water and is not suitable for consumption.

• Notify VDH of an algae bloom or fish kill, use the online HAB report form.

If you suspect you or your animal experienced health-related effects following contact with a bloom, contact the Virginia Harmful Algal Bloom Hotline at (888) 238-6154.

The Virginia Harmful Algal Bloom Task Force (VDH, Virginia Department of Environmental Quality, Old Dominion University Phytoplankton lab, and Virginia Institute of Marine Science) respond to bloom events to protect public health during the recreational season of May through October. Most algal blooms will go away when temperatures drop and sunlight is reduced in fall and winter months.