The presence of viruses on everyday surfaces has been a topic of public interest, particularly concerning the spread of COVID-19. Paper products are ubiquitous in daily life, ranging from mail and newspapers to cardboard packaging and currency. Understanding how long the virus that causes COVID-19, SARS-CoV-2, can persist on these materials helps clarify potential transmission routes and informs public health practices.
How Viruses Survive on Surfaces
Viruses are microscopic agents that require a host cell to replicate, but they can remain infectious for varying periods outside a living organism. SARS-CoV-2 is an enveloped virus, meaning it has an outer lipid membrane that can be susceptible to environmental conditions. Enveloped viruses are generally more vulnerable to desiccation, heat, and detergents compared to non-enveloped viruses. However, even with this sensitivity, SARS-CoV-2 can still retain infectivity for hours to several days on inanimate surfaces. Over time, the viral particles on a surface degrade, leading to a reduction in the concentration of viable virus.
COVID-19 Survival on Paper
Studies investigating the persistence of SARS-CoV-2 on paper surfaces have shown a range of survival times, influenced by the specific type of paper and experimental conditions. For common materials like cardboard, the virus has been detected for up to 24 hours.
On regular printing paper or tissue paper, the virus tends to become non-infectious much more quickly. Some studies report that SARS-CoV-2 does not survive on print or tissue paper for more than 3 hours. One study found viral viability for as short as 30 minutes on paper. However, other findings suggest that on certain paper types, particularly paper banknotes, the virus can persist for longer, sometimes up to 4 days or even 28 days under specific laboratory conditions (e.g., 20°C). This wide variation highlights the influence of experimental design and the specific characteristics of the paper material being tested.
Factors Affecting Viral Persistence on Paper
The duration for which SARS-CoV-2 remains infectious on paper is influenced by several environmental and material factors. Temperature plays a significant role, with higher temperatures generally leading to faster viral inactivation. For instance, virus survival on some surfaces declines to less than a day at 40°C, with inactivation occurring more rapidly at 40°C compared to 20°C.
Humidity also impacts viral persistence, though its effect can be complex. Some studies indicate enhanced viral survival at very low (20%) and very high (80%) relative humidity, with faster inactivation at moderate humidity levels (around 50%). Conversely, other research suggests that increasing humidity can accelerate viral decay. Initial viral load also affects how long infectious particles can be detected.
The characteristics of the paper itself are important determinants of viral survival. Porous materials like paper and cotton tend to absorb moisture, which can lead to faster drying of viral droplets and quicker inactivation of the virus compared to non-porous surfaces. Exposure to direct sunlight, particularly its ultraviolet (UV) component, is also known to rapidly inactivate the virus.
Everyday Safety and Paper Products
The risk of contracting COVID-19 through contact with contaminated surfaces, including paper products, is generally considered low. Quantitative risk assessments have estimated the chance of infection from surface contact to be less than 1 in 10,000.
Despite the low risk, practicing general hygiene remains a prudent measure. Handwashing with soap and water after handling common items, especially after returning from public places, is beneficial. For mail, newspapers, and other paper deliveries, the time spent in transit often allows for significant viral degradation, further reducing any potential risk.
Regarding cleaning, routine cleaning with soap or detergent once a day is typically sufficient for most surfaces to substantially reduce virus levels. Specific disinfection of paper products is often impractical and generally unnecessary for preventing COVID-19 transmission in most settings, unless there has been a known or suspected case of COVID-19 in the immediate vicinity.