Growing up, we were no doubt forced by Mom or Dad to wash our hands before dinner to remove germs. The “germs” that our parents feared lived in the grime on our hands and under our fingernails from playing in the dirt. Now, hand hygiene is being recommended even when our hands are clean! Even though most of us no longer play in the dirt (exception garden enthusiasts), we are aware that our hands can carry a host of microorganisms that may result in infection in ourselves, or those we care for, or prepare for. Our healthcare facilities promote cleansing of healthcare worker hands before and after performing personal functions, and care of each patient. And, visitors are now encouraged to cleanse their hands with one of numerous alcohol-based cleanser hand-pump on the premises.
Outbreaks of “superbugs” in healthcare facilities, and gastrointestinal infections or respiratory infections that have spread through daycares, schools, universities, long term care facilities and other environments where groups of individuals live or work in close contact have created an almost hysteria about infection and disease. Manufacturers of hand cleansers and disinfectants have paid close attention to the potential for hysteria-based income derived through products designed to protect us from the myriad of germs in our environments. Promotional advertisements warn of the hazards and encourage us to sterilize our world of germs, and there are numerous products to accomplish the goal.
Manufacturers of waterless hand-cleansers have certainly benefited from stricter infection control practices in healthcare facilities and a paranoid, although often misinformed, public. Use of alcohol-based hand cleansers (e.g. Purell, Manorapid) has been encouraged to prevent the spread of bacterial and viral infections. There is no doubt that alcohol is effective in killing vegetative bacteria (not spores), including antibiotic-resistant bacteria, Mycobacterium tuberculosis (the bacteria responsible for tuberculosis [TB]), and various fungi (CDC), but it is possible that we have a somewhat false sense of security if we assume that alcohol-based cleansers will rid our hands of viruses.
It is true that some viruses are readily inactivated by alcohol; however, some are not. Viruses consist of nucleic acid (either RNA or DNA) surrounded by a capsid (protein shell). Some viruses have an additional external layer or wrapping known as an envelope. The envelope is created from a piece of phospholipid membrane that comes from the infected host cell during the “budding” process when viral particles leave the infected cell. Enveloped viruses are referred to as lipophilic viruses, because of their lipid envelope, while nonenveloped viruses are referred to as non-lipophilic viruses.
Generally, enveloped (lipophilic) viruses are susceptible to alcohol: Herpes simplex virus (HSV), human immunodeficiency virus (HIV), influenza virus (Flu), respiratory syncytial virus (RSV), vaccinia virus, Hepatitis B and C viruses are considered susceptible to alcohols. However, certain nonenveloped (nonlipophilic) viruses such as hepatitis A and enteroviruses, which are both responsible for viral gastrointestinal infections. Depending on the alcohol concentration of the hand-cleanser and time of exposure to the alcohol, hepatitis A and other nonlipophilic viruses may not be eliminated.
Alcohol kills microorganisms by denaturing proteins and the most effective alcohol preparations have contain 60-95% alcohol. Higher concentrations are less effective because proteins are not denatured easily in the absence of water. Most commercial hand-cleansers contain between 65-70% alcohol. Nonenveloped viruses require slightly higher alcohol concentrations for reliable inactivation than are found in many commercial hand-cleansers (70-80%).
The effectiveness of alcohol in ridding hands of potentially infectious microorganisms is dependant not only on the alcohol concentration, but the time of exposure, and the volume of alcohol as well. It is important to ensure adequate contact between the cleanser and the then hands. Although the optimal volume of alcohol-based cleanser has not been determined, it is suggested that if hands feel dry after rubbing hands together for 10-15 seconds, an insufficient volume was likely applied.
Further reading:
Reducing Patient Infections Sources
Source:
Centers for Disease Control and Prevention. Guideline for Hand Hygiene in Health-Care Settings: Recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force. MMWR 2002;51 (No. RR-16):pp 10-22.
