Evaluation of Thermal Inactivation and Chemical Disinfection Efficacy Against Lassa Virus

Lassa virus (LASV), the causative agent of Lassa fever, must be handled under biosafety level 4 (BSL-4) conditions, requiring validated inactivation protocols to ensure laboratory and public safety. Although LASV is an enveloped virus theoretically susceptible to physical and chemical inactivation methods, quantitative data on its inactivation kinetics remain limited. This study systematically evaluated the efficacy of thermal treatment (56 °C, 70 °C, 95 °C), laboratory chemical inactivants (beta-propiolactone, formaldehyde, methanol, TRIzol), and five commercial disinfectants against infectious LASV. Viral infectivity was determined by titrating residual virus in Vero E6 cells, and complete inactivation was verified by three consecutive blind passages. Thermal inactivation was achieved at 56 °C for 40 min, 70 °C for 5 min, and 95 °C for 2 min. Both 0.1% and 0.05% beta-propiolactone completely inactivated LASV after 24 h at 4 °C, while 4% formaldehyde, 50% methanol, and 25% TRIzol achieved complete inactivation within 15 min, 10 min, and 2 min, respectively. For surface disinfection, 2% and 5% Micro-Chem Plus™ and 75% ethanol reduced viral titers by ≥4 log₁₀ TCID₅₀/mL within 30 s; 1% sodium hypochlorite and 0.25% Virkon required 1 min, whereas 3% hydrogen peroxide required 3 min to achieve the same reduction. These results provide quantitative, evidence-based parameters that can serve as a valuable reference for the safe handling of LASV under controlled BSL-4 laboratory conditions.