Plague Detected at Lake Tahoe

Health

Aug 20

Current Case and Immediate Impact

A South Lake Tahoe resident has tested positive for plague, marking the first confirmed human case in El Dorado County since 2020. The individual is believed to have contracted the disease through a flea bite while camping in the South Lake Tahoe area and is currently recovering at home under medical supervision.nbcnews+2

Geographic Areas Affected

Primary Affected Region

The current case is specifically linked to the South Lake Tahoe area within El Dorado County. This region is part of the broader Tahoe Basin, which has shown consistent plague activity in recent years.tahoedailytribune+2

Surveillance Data Shows Widespread Basin Activity

Between 2021 and 2024, surveillance efforts identified 41 rodents (ground squirrels and chipmunks) with evidence of plague exposure throughout the Tahoe Basin. In 2025 alone, four additional rodents have tested positive, all within the Tahoe Basin area.sfgate+2

Historical Plague Activity Areas

Fallen Leaf Campground: Previously experienced plague outbreaks requiring temporary closures and pesticide treatments in 2016~sierrasun+2~
Taylor Creek Recreation Area: Site of plague-positive chipmunk discoveries~cal-nevada~
Crane Flat and Tuolumne Meadows: Historical plague activity in nearby Yosemite National Park~cdph.ca+2~

Plague Warning Sign from South Lake Tahoe

Mitigation Plans and Response Measures

Current Public Health Response

El Dorado County health officials, in coordination with the California Department of Public Health (CDPH), have implemented several key mitigation strategies:nbcnews+1

Ongoing Surveillance: The CDPH routinely monitors rodent populations for plague activity throughout California, with particular focus on the Tahoe Basin.cdph.ca+2

Public Education Campaign: Authorities are actively disseminating prevention guidelines through multiple channels, emphasizing proper precautions for outdoor activities.usda+2

Coordinated Monitoring: State and local health officials continue surveillance of plague-prone areas, with residents encouraged to report sick or dead rodents to El Dorado County Environmental Management.tahoedailytribune+1

Historical Mitigation Protocols

Past plague outbreaks in the area have demonstrated established response procedures:sierrasun+2

Temporary Area Closures: When plague risk increases significantly, campgrounds and recreational areas may be temporarily closed for treatment.

Pesticide Treatment: DeltaDust, a pyrethroid pesticide with minimal effects on humans and pets, is applied to rodent burrows to reduce flea populations that can carry plague.tahoedailytribune+1

Enhanced Warning Systems: Plague warning signs are posted in affected areas, with standard plague caution signs maintained throughout endemic regions.usda+1

Risk Assessment for Other Northern California Areas

Endemic Plague Regions

Plague is naturally endemic throughout much of Northern California's mountainous and foothill regions. The disease occurs primarily in the following areas:plumascounty+2

Sierra Nevada Mountains: Including areas around Lake Tahoe, extending throughout the mountain chain~cdph.ca+2~
Northern California Foothills: Encompassing multiple counties in foothill and mountainous terrain~plumascounty+1~
Cascade Mountains: Including areas in northeastern California~bioone~

Specific Risk Areas Beyond Lake Tahoe

Yosemite National Park: Historical plague activity with confirmed human cases in 2015, demonstrating that the risk extends beyond the immediate Tahoe Basin. Surveillance has documented plague activity at multiple locations within the park, including Crane Flat Campground and Tuolumne Meadows.latimes+3

Central Sierra Nevada: Research indicates plague foci are associated with high-elevation rodent communities throughout the Sierra Nevada range, with environmental conditions becoming increasingly favorable for plague maintenance.pmc.ncbi.nlm.nih

Northern Sierra Nevada: Long-term surveillance from 1970-1997 documented sustained plague activity among wild rodents in coniferous forest habitats, particularly affecting chipmunks and pine squirrels.bioone

Climate-Related Risk Trends

Recent scientific analysis suggests that plague risk in Northern California may be increasing due to environmental changes. Since 1950, plague suitability has increased by 30-40% in some high-elevation areas of the western United States, with conditions becoming more conducive to plague reservoir establishment.nature+1

Lakes and Rivers Risk Assessment

Direct Water Body Risk

Plague is not transmitted through water itself, but rather through infected fleas and rodents that inhabit areas around water bodies. However, popular recreational areas near lakes and rivers in Northern California endemic regions carry associated risks:nbcnews+2

High-Risk Recreation Areas: Camping, hiking, and outdoor activities near lakes and rivers in the Sierra Nevada, including areas around Donner Lake, various Sierra Nevada lakes, and foothill reservoirs, occur within known plague endemic zones.usda+2

Vector Habitat: The interface between recreational water areas and natural rodent habitat creates exposure opportunities, particularly in campgrounds and picnic areas where human-rodent contact is more likely.cdph.ca+1

Regional Risk Distribution

Current plague endemic areas in Northern California include counties with significant lake and river recreational resources:plumascounty+1

El Dorado County: Contains Lake Tahoe and numerous Sierra Nevada recreational areas
Placer County: Includes multiple Sierra Nevada lakes and the American River system
Nevada County: Contains various Sierra Nevada water recreational areas
Tuolumne County: Encompasses areas near Yosemite and Don Pedro Reservoir

Prevention Recommendations

For Outdoor Recreation

Avoid contact with all wild rodents, whether alive or dead~tahoedailytribune+2~
Do not camp near animal burrows or areas with dead rodents~nbcnews+2~
Wear long pants tucked into boots and apply DEET-based insect repellent~tahoedailytribune+2~
Keep pets on leashes and protect them with flea control products~usda+2~
Store food in rodent-proof containers~usda~

Reporting and Medical Attention

Individuals should report sick or dead rodents to El Dorado County Environmental Management at (530) 573-3450. Anyone experiencing fever, nausea, weakness, and swollen lymph nodes after outdoor activities in endemic areas should seek immediate medical attention and inform healthcare providers of potential plague exposure.nbcnews+2

The current plague case at Lake Tahoe represents ongoing endemic disease activity rather than a new outbreak, with established surveillance and response systems in place. While risk remains low for individuals taking proper precautions, the broad distribution of plague throughout Northern California's mountainous regions means that outdoor recreation in these areas requires consistent vigilance and adherence to prevention guidelines.