In an important update, the Virginia Department of Health (VDH) has announced the closure of its investigation into the Shiga toxin-producing Escherichia coli (STEC) outbreak associated with Lake Anna over the Memorial Day weekend. The outbreak, which initially raised significant public health concerns, has seen thorough surveillance and investigation efforts by local, state, and federal partners. As of June 28, 2024, the outbreak investigation is officially closed.

Outbreak Investigation Summary

The VDH’s investigation focused on an outbreak of STEC, which involved individuals who visited the Lake Anna area between May 24 and May 27, 2024. In total, 25 STEC cases were identified, with 12 caused by the most common type, STEC O157. Of these 25 cases, 23 were linked to people who visited the lake during the Memorial Day weekend, while two were from close contacts of those infected. The absence of new cases among visitors to Lake Anna after Memorial Day indicates that the period of greatest risk has passed.

Environmental Testing and Water Quality

The Virginia Department of Environmental Quality (DEQ) conducted extensive water sampling from Lake Anna, particularly from areas such as the Sandbar, Cocktail Cove, and Lake Anna State Park. The latest water samples, collected on June 25, showed fecal bacteria levels well below the public health concern threshold. However, additional testing to detect specific STEC strains is still pending.

It is likely that the STEC infections are a result of exposure to lake water over Memorial Day weekend. However, the presence of STEC O157 bacteria in the water samples has not yet been confirmed, as laboratory testing is still in progress. It is unlikely that VDH will be able to specifically identify the source of bacteria in the water.

Potential sources of contamination include environmental pollution from:

• Heavy rains
• Livestock
• Failing septic systems
• Boating discharge
• Swimmers

Safety Measures and Recommendations

Despite the closure of the investigation, VDH advises the public to remain cautious when engaging in water activities. Natural bodies of water, including Lake Anna, are not disinfected, posing inherent health risks. The VDH encourages visitors to follow safety guidelines to minimize the risk of illness:

1. Do Not Swallow Water: Avoid swallowing untreated water while swimming.
2. Personal Hygiene: Wash hands frequently, especially after swimming, using the bathroom, and before eating.
3. Post-Swim Care: Shower or bathe after swimming to remove potential contaminants.
4. Water Quality Awareness: Check for green films or unusually cloudy water, and avoid swimming near storm drains or livestock.
5. Health Precautions: Refrain from swimming if you have cuts, open wounds, or are experiencing vomiting or diarrhea.
6. Post-Rain Safety: Avoid swimming for three days following heavy rains due to potential runoff contamination.

Algal Blooms & More Info

Currently, some parts of Lake Anna are affected by a harmful algal bloom (HAB). Visitors are urged to check the interactive HAB map before heading to the lake and to avoid swimming in areas under advisory.

The VDH’s closure of the STEC outbreak investigation marks a significant milestone in ensuring public health safety. However, the department will continue enhanced surveillance for STEC through July 17, especially with the upcoming 4th of July celebrations. This includes monitoring emergency department and urgent care visits for gastrointestinal illnesses. The DEQ will also maintain its routine water quality monitoring from April to October.

For more information on how to stay safe during water activities, visit www.swimhealthyva.com and the CDC’s How to Safely Visit Oceans, Lakes, and Rivers website. By staying informed and taking appropriate precautions, visitors can enjoy the natural beauty of Lake Anna safely.

For any further updates, please refer to the VDH website and keep abreast of any new information regarding water safety and public health advisories.

Jen Bailey

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