‘You would want to think twice about swimming’: Advisory issued for northern Lake Anna in Virginia

FILE — This Wednesday, Aug. 15, 2018 aerial photo shows Dominion Energy's North Anna Power Station along the shores of Lake Anna in Mineral, Virginia. (AP Photo/Steve Helber, file)(AP/Steve Helber)

Shortly after Virginia Department of Health (VDH) officials announced Lake Anna was “likely the source” of an E. coli outbreak that sickened 25 people, a swimming advisory was issued for the lake for a separate danger — a harmful algae bloom.

On Friday, VDH said people are advised to avoid contact with the upper section of the North Anna Branch of Lake Anna in Louisa County. This section of the lake, located above Route 522, is reported to have unsafe levels of cyanobacteria — which can cause skin rashes and gastrointestinal illnesses, such as an upset stomach, nausea, vomiting and diarrhea.

According to VDH, activities that pose a risk of ingesting water should be avoided, but boating with proper precaution can continue.

The VDH also specified in the release that the algae bloom is “not associated with the outbreak of Shiga toxin-producing Escherichia coli (STEC) at Lake Anna area, as that pathogen is not associated” with the bloom.

Margaret Smigo, waterborne hazards program coordinator at VDH, said Lake Anna has a history of harmful algal blooms and phytoplankton usually increase with warm weather and sunlight.

“The samples that were collected for harmful algal bloom response were collected on Monday and the levels in the North Anna were just above our threshold for the harmful algal bloom advisory,” said Smigo. “And we did detect very slight concentrations of one cyanotoxin, but it was well below levels that would pose a human health concern.”

Smigo said it takes approximately one month to get an advisory lifted, which includes about two samples taken 10 days apart in between the logistics of sampling, analysis and review.

Meanwhile, 25 people, including seven children, are still recovering after spending Memorial Day weekend at the lake and becoming seriously sick. According to VDH, they eliminated the possibility of food contamination and say the “likely source” for the E. coli outbreak was Lake Anna.

“We aren’t able to give an exact source,” said Smigo. “Unfortunately, that’s very rarely the case during outbreaks, especially when you have a variety of different illnesses where you have a holiday weekend, several folks were out of town, and you also have the potential for recreational water exposure. The recreational water exposure, or lake water, seems to be the most likely source of illness.”

Smigo said the organization came to this possible conclusion by simply doing a process of elimination. Officials say samples of the water collected June 11 and on Monday showed the fecal bacteria concentrations were well below a level of concern, and they plan to test again on Tuesday.

VDH also said animals that have been in the lake could be how the water was contaminated, but they aren’t able to say when that may have happened. The weather could also be the cause of pollutants.

“Following that rain event, VDH strongly recommends that the public not go swimming in natural water bodies two to three days after a rain event,” said Smigo. “And this is because it takes a while for the disturbance of that rain to kind of settle out. The benefit of rain is that it provides dilution of more water, but it is also dragging pollution with it once it hits the ground and moves towards the water body itself.”

When asked if it is safe for people to swim in Lake Anna once the algal advisory is lifted, Smigo said it’s very important for people to look at what level of risk they’re comfortable with. And they have to make that decision for themselves as well as for their family.

She reminds people that swimming in natural water isn’t like a swimming pool where chlorine or some other method is used to clean the water and bring bacteria levels down.

“I think it’s important that we realize that there could always be some level (of bacteria) present,” said Smigo. “And that if you have, let’s say underlying health conditions, if you happen to be pregnant, if you have diabetes, COPD, if you’re a child under five, or if you are older in age and don’t have robust immunity … these are all examples of how you might have less immunity than someone who doesn’t have that underlying condition. So if you meet one of those qualifications, or someone you love does, you would want to think twice about swimming in a natural body of water.”

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Cheyenne Corin

Cheyenne Corin joined the WTOP News team in February 2023. Prior to this role she was a Montgomery County, Maryland, bureau reporter at WDVM/DC News Now.

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