In a recent study published in Emerging Infectious Diseases, researchers demonstrated the efficacy of two World Health Organization (WHO)‒really helpful alcohol-based hand rub solutions to inactivate the monkeypox virus (MPXV).

Study: Efficient Inactivation of Monkeypox Virus by World Health Organization‒Beneficial Hand Rub Formulations and Alcohols. Image Credit: MIA Studio/Shutterstock

Background

Implementing hygienic hand measures to preclude healthcare- and outbreak-triggering lethal viral infections is significant. Thus, in 2009, the WHO proposed and implemented two alcohol-based formulations, I and II, for surgical and hygienic hand disinfection in healthcare settings. Nonetheless, researchers haven’t assessed their inactivation efficacies against MPVX.

A concerning fact about MPXV that makes it a public health concern is that it’s spreading amongst individuals who haven’t traveled to disease-endemic areas. Its clinical and epidemiologic patterns are novel, unlike prior outbreaks. Also, it’s remarkably more stable than other pox viruses. It’s thus mandatory to verify which disinfectants and biocidal agents can effectively inactivate MPXV.

The study

In the current study, researchers obtained virus isolate MPXV-DUS_001 from a patient in Düsseldorf, Germany, who was infected early throughout the 2022 MPXV outbreak. They passaged this isolate twice on Vero 76 cells before experimental use.

First, the team cultured Vero 76 cells in Dulbecco modified Eagle (DME) medium and seeded them at a concentration of 0.33 × 106 cells/mL for MPXV preparation. Next, following a change of medium, they inoculated these cells with MPXV at a multiplicity of infection (MOI) of 0.01. The team incubated Vero 76 cells at 37°C until they observed a visual cytopathic effect (CPE). They moved on to harvesting MPXV-infected cells by scraping, then extensive vortexing and subsequent extraction of the infectious supernatant from cell debris by centrifugation. Finally, the researchers aliquoted and titrated virus suspensions per standard protocols and stored them at −80°C for future use. The researchers confirmed that MPXV-DUS_001 was MPXV clade II using panorthopoxvirus‒specific quantitative, real-time reverse transcription polymerase chain response (qRT-PCR).

The team adhered to the European guideline EN14476 to evaluate the virucidal activity of WHO formulations I and II. Since these formulations are 80% ethanol and 75% isopropanol-based, additionally they evaluated the MPXV susceptibility against ethanol and 2-propanol. The protocol mandated mixing eight parts of disinfectant with one a part of bovine serum albumin and MPXV each to achieve a final concentration of 0.3 g/L. The suspension was then vortexed and incubated for 30 seconds at room temperature.

They performed an endpoint dilution assay on Vero 76 cells and evaluated CPE microscopically after seven days. Next, they computed the 50% tissue culture infectious dose (ID50) per milliliter for all 4 disinfectants at final concentrations of 20%, 30%, 40%, 60%. and 80%. Finally, the researchers used a suspension test to look at the virucidal activity of the WHO formulations I and II against MPXV.

Study results

MPXV showed sensitivity to each WHO formulations but was also probably the most stable amongst all viruses tested, including modified vaccinia Ankara. Each formulations efficiently inactivated MPXV with reduction aspects (RFs)>6.7 at concentrations of 60% and 80% volume/volume (v/v). Remarkably, the WHO formulation II remained effective against MPXV even at a dilution of 40% (vol/vol) with an RF of 6.6. Conversely, WHO formulation I at an identical concentration couldn’t reduce MPXV titers.

The researchers noted that each ethanol and 2-propanol reduced MPXV titers to background levels with RFs >6.7 at >60% and >40% (v/v) concentrations, respectively. With RF=6.6, 40% ethanol (v/v) nearly inactivated MPXV completely. Nonetheless, with RF=5.3, 30% v/v 2-propanol achieved the identical virucidal activity.

Conclusions

Overall, the study results showed that MPXV showed the very best stability to each WHO formulations compared with other (re)emerging orthopox family viruses. Infectious MPXV persists in a household environment for greater than 15 days. Due to tight binding with fibrin matrixes of scab material, virions shed from lesions are much more immune to desiccation than other enveloped viruses (e.g., influenza virus). The high stability of MPXV necessitates a comprehensive reevaluation of current hygiene measures. Thankfully, each tested WHO formulations effectively inactivated MPXV, supporting their use in healthcare systems and through MPXV outbreaks. To conclude, the study showed that the timely application of alcohol-based disinfectants could effectively minimize MPXV spread throughout the ongoing MPVX outbreak.