Which of the following disinfectants is most effective against non-enveloped viruses and is commonly used for surface decontamination in hospital operating theatres?

Explanation

## Sodium Hypochlorite for Non-Enveloped Virus Disinfection ### Why Sodium Hypochlorite is Superior **Key Point:** Sodium hypochlorite (bleach) at 5% concentration is a broad-spectrum oxidising agent that is highly effective against non-enveloped (naked) viruses, which are notoriously resistant to many disinfectants. ### Mechanism of Action Sodium hypochlorite generates hypochlorous acid (HOCl), which oxidises viral proteins and nucleic acids, disrupting the viral capsid structure and rendering the virus non-infectious. This mechanism is effective even against the most resistant pathogens. ### Comparison of Common Disinfectants | Disinfectant | Concentration | Enveloped Viruses | Non-Enveloped Viruses | Spores | Best Use | |--------------|----------------|-------------------|----------------------|--------|----------| | **Sodium Hypochlorite** | 5% | Excellent | **Excellent** | Good | Surface decontamination, OT, laboratory | | **70% Ethanol** | 70% | Good | Poor | No | Skin antisepsis, hand rub | | **Chlorhexidine + Alcohol** | 0.5% + 70% | Good | Moderate | No | Skin antisepsis, wound irrigation | | **Hydrogen Peroxide** | 3% | Moderate | Moderate | Moderate | Wound cleaning, instrument disinfection | **High-Yield:** Non-enveloped viruses (poliovirus, rotavirus, norovirus, adenovirus) are resistant to alcohols, phenolics, and quaternary ammonium compounds because they lack a lipid envelope. Only oxidising agents (chlorine, ozone, hydrogen peroxide at high concentrations) and aldehydes reliably inactivate them. **Clinical Pearl:** In hospital operating theatres and high-risk areas, 5% sodium hypochlorite is the standard choice for disinfecting surfaces contaminated with faecal matter or blood-borne non-enveloped viruses (e.g., hepatitis A, norovirus outbreaks). **Mnemonic:** **"Bleach Beats Naked Viruses"** — sodium hypochlorite (bleach) is the oxidiser of choice for non-enveloped (naked) viral pathogens. ### Why Other Disinfectants Are Inferior for Non-Enveloped Viruses 1. **70% Ethanol:** Excellent for enveloped viruses (disrupts lipid envelope) but **poor** against non-enveloped viruses; alcohol cannot penetrate or disrupt the protein capsid effectively. 2. **Chlorhexidine + Alcohol:** Good for skin antisepsis but only **moderately** effective against non-enveloped viruses; primarily targets bacterial cell membranes. 3. **Hydrogen Peroxide:** Has some oxidising activity but is less potent than chlorine-based agents and is slower-acting against non-enveloped viruses.