Virginia Department of Health completes investigation into Memorial Day outbreak at Lake Anna

The Virginia Department of Health (VDH) reports that recent tests of water samples from Lake Anna not Detection of Shiga toxin-producing Escherichia coli (STEC) O157. Additional results of fecal bacteria in the water samples did not reveal levels that would normally raise health concerns. VDH reminds the public that a swim advisory remains in effect for the upper section of the North Anna Branch of Lake Anna in Louisa County due to harmful algal blooms not related to this STEC outbreak.

VDH is completing its investigation into the STEC outbreak associated with exposure to Lake Anna over the Memorial Day weekend. More than 20 days have passed (two 10-day incubation periods) since the last person who visited Lake Anna over the holidays became ill. Laboratory testing by the Virginia Department of General Services’ Division of Consolidated Laboratory Services (DCLS) failed to identify STEC O157 bacteria in water samples from the lake. In addition, VDH was unable to identify the source of the bacteria in the water.

Water tests are snapshots of a specific location. The samples used for STEC testing were collected approximately four weeks after Memorial Day weekend and may not reflect the water environment during the holiday weekend. These results also cannot predict future risks. Swimming or other activities in natural waters always pose some health risk because the water is not disinfected. Children under five, older adults, and people with weakened immune systems are at higher risk of contracting diseases in natural waters.

Due to the upcoming Fourth of July celebration, VDH will conduct enhanced public health surveillance through July 17. Information will be provided as it becomes available. This surveillance includes monitoring emergency department and urgent care visits and investigating any STEC case reported by a healthcare provider. VDH and its local health departments will continue to work with local partners to better understand potential risks in the area and develop prevention strategies to address those risks. DEQ will continue routine bacterial surveillance of Lake Anna that occurs between April and October each year. This surveillance includes testing for fecal bacteria, but not for STEC. DEQ results are available on the Water Quality Data Home.

To prevent illness while swimming, boating, wading, or recreationally engaging in natural waters, individuals should:

• Never swallow untreated water and do not swim if your skin has cuts or open wounds.
• Wash your hands frequently, including after swimming and before preparing and eating food.
• Shower or bathe after swimming to wash away any germs and contaminants.
• Check the water and surrounding area before swimming. Do not enter the water if there is a green film on the water or the water is cloudier than usual. Do not swim near sewers or livestock.
• Avoid swimming if you are vomiting or have diarrhea.
• Avoid swimming for three days after a heavy rain. Heavy rain picks up everything it comes into contact with, including germs from overflowing sewers, polluted stormwater, and runoff from land.
• Properly dispose of human waste by discharging boat wastewater at marinas using a pumping unit or disposal station.
• Consult your doctor before swimming in the sea, lakes, rivers or other natural bodies of water if your body’s defenses against germs are already compromised by other health problems or medications.

VDH and the Virginia Harmful Algal Bloom Task Force will continue to monitor water quality in the lake for HAB. Generally, warnings are lifted after two consecutive test results with acceptable levels of algal cell counts and/or toxin concentration. For additional recommendations for healthy behaviors during water activities, visit www.SwimHealthyVA.com and the CDC’s How to Visit Oceans, Lakes, and Rivers Safely website.