Cold sores, or fever blisters, are a widespread viral infection caused by the herpes simplex virus type 1 (HSV-1). While often appearing around the mouth, HSV-1 can affect other body areas. A key concern is how long this virus persists on inanimate surfaces, which impacts its potential for indirect transmission.
Understanding Viral Survival on Surfaces
HSV-1 can survive on various surfaces outside the human body, though its viability depends on environmental conditions. While direct skin-to-skin contact remains the primary mode of transmission, indirect transmission through contaminated objects is possible. As an enveloped virus with an outer lipid layer, HSV-1 is generally more susceptible to environmental factors than non-enveloped viruses.
Studies show HSV-1 can persist on dry surfaces from a few hours to several days. For instance, it survives up to two hours on skin, three hours on cloth, and four hours on plastic. Some research indicates HSV-1 can remain viable on dry surfaces for up to seven days, making fomites a potential transmission concern. The virus’s inactivation rate is high on environmental surfaces, especially with drying.
Factors Influencing Survival Time
Several environmental conditions and surface characteristics impact how long HSV-1 remains viable on objects. Temperature plays a significant role, with the virus surviving longer at lower temperatures. For example, HSV-1 showed no loss of infectivity for at least an hour at refrigerator temperature (2°C), but a substantial drop at room temperature (22-24°C) as droplets dried.
Humidity is another influential factor; HSV-1 tends to survive longer in lower humidity. Light exposure, particularly ultraviolet (UV) light, can also inactivate the virus, though a germicidal lamp did not completely inactivate HSV-1 after 15 minutes in one study. The type of surface also matters; drying of virus-containing droplets can significantly reduce viability.
Preventing Spread via Contaminated Objects
To minimize indirect cold sore transmission from contaminated objects, several practical steps can be taken. Practicing good hand hygiene is an effective measure, especially after touching a cold sore or any potentially contaminated item. Washing hands carefully before touching oneself or others, particularly infants, is important.
Cleaning and disinfecting shared items is another preventative action. HSV-1 is highly susceptible to routinely used hospital-grade disinfectants. Disinfectants like bleach, isopropanol, and quaternary ammonium compounds effectively inactivate the virus. A 1% sodium hypochlorite (bleach) solution, made fresh daily with a 15-minute contact time, is a highly effective disinfectant for reusable equipment, surfaces, and liquid waste. Avoiding the sharing of personal items—such as drinking glasses, coffee mugs, straws, washcloths, towels, lip balms, and razors—is also recommended, especially during an outbreak.