What infectious hazards are associated with a mouse infestation in a home?

Infectious Risks of Mice in the Home

Mice in homes pose serious infectious disease risks including hantavirus pulmonary syndrome (a potentially fatal respiratory illness), bacterial gastroenteritis from Salmonella and Shigella, leptospirosis, toxoplasmosis, and in the western United States, plague transmitted through rodent fleas. 1, 2, 3

Primary Infectious Hazards

Hantavirus Pulmonary Syndrome (HPS)

• Most critical threat: Deer mice and other wild rodents carry hantaviruses that cause HPS, a severe respiratory disease with significant mortality risk 1, 2
• Transmission occurs through inhalation of aerosolized virus from rodent urine, droppings, or saliva—as little as 5 minutes of exposure in contaminated areas can cause infection 2
• Subclinical infection is uncommon; most exposures result in clinically apparent disease 2
• Person-to-person transmission does not occur with North American hantaviruses 2

Bacterial Pathogens

• Urban house mice carry multiple gastrointestinal pathogens: Shigella, Salmonella, Clostridium difficile, and diarrheagenic E. coli were detected in 416 mice surveyed across New York City residential buildings 3
• These bacteria cause febrile illness and severe gastroenteritis in humans 3
• Mice also harbor antimicrobial resistance genes (fluoroquinolone and β-lactam resistance), complicating treatment 3

Leptospirosis

• Pathogenic Leptospira species were detected in mouse kidney samples, indicating mice serve as reservoirs for this potentially severe bacterial infection 3

Toxoplasmosis

• 59% of urban house mice tested positive for Toxoplasma gondii in Manchester, UK residential properties 4
• Evidence of vertical transmission from infected mothers to fetuses maintains infection cycles in urban mouse populations 4
• Poses particular risk to pregnant women (causing spontaneous abortions and fetal abnormalities) and immunocompromised individuals 4

Plague (Geographic-Specific)

• In the western United States (west of the 100th meridian), rodent fleas transmit plague to humans 1
• This risk requires specific precautions when handling dead rodents or cleaning heavily infested areas in these regions 1

Critical Clinical Context

When to Suspect Rodent-Borne Illness

Suspect hantavirus infection in patients with febrile or respiratory illness within 45 days of: 2

• Occupying or cleaning previously vacant cabins with rodent infestation
• Cleaning barns and outbuildings
• Disturbing rodent excreta or nests
• Handling mice without gloves
• Hiking or camping in endemic areas
• Hand plowing or planting in rural settings

Diagnostic Timing

• Any febrile or respiratory illness within 45 days of potential rodent exposure requires immediate evaluation 2
• Blood samples should be obtained and forwarded to state health departments for hantavirus antibody testing 2

Prevention Priorities

Immediate Actions for Households with Mice

Rodent exclusion is the primary prevention strategy 1, 5:

• Seal all gaps and holes >¼-inch (>6 mm) in diameter inside and outside the home using cement, lath metal, hardware cloth, or steel wool with caulk 1
• Inspect twice yearly for entry points around pipes, windows, doors, appliances, and utility lines 1

Eliminate food and water sources 1, 5:

• Store all food, water, and pet food in rodent-proof containers 1, 5
• Wash dishes immediately after use and remove all food debris 1
• Dispose of trash regularly in rodent-proof containers 1, 5

Active trapping 1, 5:

• Use spring-loaded traps with peanut butter bait placed perpendicular to baseboards 1, 5
• Continue trapping for at least 1 week after the last rodent is caught 1
• Maintain several baited traps continuously as prevention against reinfestation 1

Safe Cleanup Protocols

Standard precautions for routine cleanup 1, 5:

• Wear rubber, latex, vinyl, or nitrile gloves when handling rodents or contaminated materials 1, 5
• Spray rodent urine, droppings, and dead rodents with disinfectant or 1:10 bleach solution before cleanup 1, 5
• Never vacuum or sweep until after disinfection to avoid aerosolizing infectious particles 5
• Use paper towels to pick up materials, then disinfect all surfaces 5

Heavy infestations require enhanced protection 1, 5:

• Ventilate closed buildings for at least 30 minutes before entering 1, 5
• Wear coveralls, rubber boots, protective goggles, and appropriate respiratory protection 1, 5
• Contact local or state health departments for guidance 1, 5

Western United States-specific precautions 1, 5:

• Apply DEET-containing insect repellent to clothing, shoes, and hands when handling dead rodents to prevent fleabites 1, 5
• Use insecticide before trapping in cases of heavy indoor infestation 1
• Contact local health departments to determine if plague is endemic in your area 1

Disposal of Dead Rodents

• Double-bag rodent remains after spraying with disinfectant 1, 5
• Dispose by burying 2-3 feet deep, burning, or placing in regularly emptied covered trash 1, 5

Common Pitfalls

Trapping alone is insufficient: Removing mice without sealing entry points results in immediate replacement by other mice from outside 1

Brief exposure is dangerous: Even 5 minutes in areas with infected rodents can transmit hantavirus 2

Hantaviruses are environmentally fragile: They survive <1 week indoors and only hours in sunlight, making disinfectants highly effective 1

Professional help is warranted: For severe or persistent infestations, contact pest-control professionals for eradication and building contractors for rodent-proofing 1