Keyboard Germs: Ready to Travel... and Infect

Computer Keyboards as Vectors of Disease – A Problem More Serious than Previously Thought

It seems reasonable to think that the greater the number of people who touch a common surface, the greater the likelihood that germs will be transferred from people to the surface and from the surface to other people. One would think that restrooms, especially toilet seats and doorknobs, harbor the most germs, but this turns out not to be true. ATM keyboards were found to have more germs than a public restroom door, according to one researcher.[1]

Fingered, breathed on, sneezed on, coughed on, talked over, eaten over, and spilt upon, keyboards are really dirty.

Computer keyboards, according to one microbiologist in London, are often a reflection of what’s in a person’s nose and gut.[2] Fingered, breathed on, sneezed on, coughed on, talked over, eaten over, and spilt upon, keyboards are really dirty. It’s no wonder that computer keyboards are among the top four microbe-ridden surfaces in office environments.[3]

The “germiest” office surfaces were (from most bacteria to least): telephones, desks, computer keyboards, and computer mice The average desk contains 400 times more bacteria than the average men’s toilet seat. Even copy and fax machines were dirtier, on average, than the average men’s toilet seat.[3] Surprisingly, the most germ-ridden item of all in any office was men’s wallets, with four times more microbes than on women’s wallets.[4]

The take-home message is that even inanimate objects such as computer equipment may serve as vectors for disease transmission.

Uncleaned shared computer equipment such as keyboards and mice were determined to be responsible for an outbreak of norovirus in an elementary school in Washington, D.C., resulting in acute gastroenteritis among the staff and students.[5] This was the first report showing that computer keyboards and mice were transmitters of norovirus and were linked to an outbreak of disease.[6, 7] While it seems logical that schoolchildren who are enclosed in a classroom and who do not exercise good hygiene might be an increased risk for person-to-person viral transmission, the take-home message is that even inanimate objects such as computer equipment may serve as vectors for disease transmission. The fact that a person who is ill may be infectious while symptomatic and for 3 to 14 or more days after the last symptom because of continued fecal shedding emphasizes how long an infectious cycle may persist. Most people return to work almost as soon as they feel well and don’t realize that they still harbor and shed pathogens, not only via direct person-so-person contact, but by touching inanimate objects such as keyboards, as well.[5]

At the conclusion of a five-year study, surfaces from 11% of office environments were found to be positive for biochemical markers (such as those for blood, mucus, saliva, sweat, and urine), but surfaces from shopping environments, playgrounds, and daycare centers were the most frequently contaminated
(biochemical markers detected on 21%, 36%, and 46%, respectively).[8]

It is known that 80% of infections are transmitted through the environment.[9]

Of 100 computer keyboards in 29 clinical areas of a teaching hospital in Washington, D.C., 95 tested positive for bacterial contamination, including Streptococcus, Clostridium perfringens, Enterococcus (including a vancomycin-resistant strain), Staphylococcus aureus, fungi, and gram-negative organisms.[10]

Another study in a hospital intensive care unit showed that computer keyboards and faucet handles had higher rates of bacterial colonization with methicillin-resistant Staphylococcus aureus (MRSA) and other potential pathogens than did other well-studied intensive care unit surfaces in rooms with patients who tested positive for MRSA. The results suggest that keyboards and faucet handles are among the environmental reservoirs for nosocomial pathogens and act as vectors for cross-transmission in the ICU setting.[11]

A study of 25 computer keyboards in two intensive care units and six nursing units demonstrated that 50% of keyboards harbored potential pathogens including coagulase-negative staphylococci, diphtheroids, Micrococcus species, Bacillus species, as well as some pathogens such as oxacillin-resistant and oxacillin-susceptible Staphylococcus aureus, vancomycin-susceptible Enterococcus species, and nonfermentative gram-negative rods.[12] As part of the study, keyboards were inoculated with three types of bacteria in order to determine the effectiveness of six types of disinfectant and a sterile water control. All were effective at removing or inactivating 95% of the test microorganisms.[12]

These results sound great, but how do they relate to the real world? A recent survey of more than 4,000 people conducted by Which? Computing revealed that 22% cleaned their keyboard once a month and 27% cleaned their monitor once a month; just over 10% never cleaned their keyboard, and 20% never cleaned their mouse.[13]

Computer keyboards can harbor pathogens such as vancomycin-resistant enterococci and Pseudomonas aeruginosa for more than 24 hours unless cleaned, but even after cleaning, vancomycin-resistant enterococci was recovered from 50% of the surfaces and Pseudomonas aeruginosa from 36% of the surfaces touched.[14] Although a number of disinfectants seem effective at removing bacteria, alcohol does not provide sustained antimicrobial activity against vancomycin-resistant enterococci species and Pseudomonas aeruginosa.[15] Viruses spread by coughing or sneezing can remain viable on a surface for up to three days.[9]

Even if people were to clean their computers (1) consistently on a daily basis and (2) consistently following manufacturers’ recommendation, how uniformly do they decontaminate their computers from one cleanup session to the next? With shared computers, the problem of consistency in decontamination between computer users becomes even greater.

Public computers have many users, increasing the likelihood that (1) antibiotic-resistant bacteria will be transmitted via keyboards, and (2) transmission of such antibiotic-resistant bacteria may affect their prevalence in the community setting.[16]

Consider that even when we affectionately handle our pets we are likely to transfer potential pathogens[17] from our hands to our keyboards and mice, pathogens that wait for a new host in the form of the next computer user.

And what about in between the keys? Many people eat meals or snack at their desks while they continue to work. Crumbs are almost inevitable, providing a feast for many microbes and keeping them viable for yet another transfer.

Shedding (UV) Light on the Matter

Just as certain wavelengths of light are beneficial (such as those that cause us to make Vitamin D), others are detrimental, to the point of killing cells. Certain wavelengths of light—those in the ultraviolet C (UVC) range (see below)—are considered germicidal and are used as disinfectants. UVC can induce damage to DNA that leaves a cell or virus incapable of reproducing, rendering it genetically dead.

Ultraviolet radiation

  • Ultraviolet radiation is that part of the electromagnetic spectrum emitted by the sun whose wavelengths are in the range of 100 to 400 nm. [Table 1 p 8]. These wavelengths are shorter than visible light (380 to 760 nm) and longer than X-rays (0.001 to 0.1 nm).[18]
  • Ultraviolet radiation is subcategorized into smaller ranges of wavelengths: UVA, ranging from 315 to 400 nm; UVB, ranging from 280 to 315 nm; and UVC, ranging from 100 to 280 nm.[18][Table 1 p 8] Although all of the UVC rays are absorbed by ozone layer of earth’s atmosphere, most of the UVA radiation and about 10% of the UVB radiation reach the earth’s surface and are important to human health. In small doses, UV radiation is essential for the production of vitamin D, but in large doses (overexposure), detrimental acute and chronic health effects may result on the skin, eye, and immune system (e.g., sunburn, actinic keratoses, skin cancer, and suppression of cell-mediated immunity).[19, 20]
  • Sources of UVC radiation at the earth’s surface are artificial, such as from UV lamps.[21] UVC radiation penetrates the outer surfaces of bacteria and viruses and reaches the genetic material where it causes damage that renders the microbes unable to reproduce. For this reason, UVC radiation is considered germicidal.
  • Different parts of the UVC range, though, have different effects. The FDA has deemed the longer wavelength of UVC radiation, 254 nm, to be an effective air, surface, and water disinfectant. While shorter UVC wavelengths (180 nm) are also germicidal, they produce ozone which, above a certain threshold, can pose a safety hazard to humans and animals.[22] Ozone is not a byproduct of the longer wavelength 254 nm UVC radiation.

Just 45 seconds of exposure of the keyboard to a UVC-emitting lamp provides 25,000 microwatt-seconds per square centimeter of UVC light—enough to kill most of the common germs.[23] Tests run by ATS Labs on the Keyboard Sanitizer, KBS-1 showed that in just one cycle, 99.9% of bacteria such as Staphylococcus aureus and Enterobacter aerugenes were killed, and the influenza A virus was inactivated. This level of exposure is also known to kill MRSA [23].

“This won’t create a sterile environment, but it will reduce the amount of germs with which people come into contact,” said the Keyboard Sanitizer’s inventor, Dr. Jon Roberts.[23] Given that the flu alone carries a $20 billion price tag on lost productivity caused by the average one-and-a-half days that workers stay home,[9], 45 seconds of exposing a known germ center to UVC radiation to sanitize it seems like a most reasonable, easy, and effective measure to prevent germ-induced discomfort, misery, and expense.


1. Thibodeau, P., Is Your Keyboard a Health Hazard? Here's Help, in Computerworld. 2007.
2. Keyboards 'dirtier than a toilet'. BBC News May 1, 2008 [cited August 8, 2006]; Available here: Keyboards 'dirtier than a toilet'.
3. Edelhauser, K. Is Your Office Making You Sick? February 14, 2007 [cited August 6, 2008]; Available here: Is Your Office Making You Sick?.
4. Germs Working Overtime, Especially at Women's Desks; New Study Compares Office Surfaces Germ by Germ to Determine “Germiest” Gender. Infection Control Today February 14, 2007 [cited August 6, 2008]; Available here: Germs Working Overtime, Especially at Women's Desks.
5. Norovirus outbreak in an elementary school--District of Columbia, February 2007. MMWR Morb Mortal Wkly Rep, 2008. 56(51-52): p. 1340-3.
6. Childs, D. Your Keyboard: Dirtier Than a Toilet. U.K. Microbiologist Finds E. coli, Staph on Computer Keyboards. ABC News May 5, 2008 [cited July 27, 2008]; Available here: Your Keyboard: Dirtier Than a Toilet.
7. Reinberg, S. Stomach Flu Spread By Contaminated Computer Keyboards. Women's Health in the News January 3 2008 [cited July 19, 2008]; Available here: Stomach Flu Spread By Contaminated Computer Keyboards.
8. Reynolds, K.A., et al., Occurrence of bacteria and biochemical markers on public surfaces. Int J Environ Health Res, 2005. 15(3): p. 225-34.
9. Williams, D. Is your desk making you sick? Health. November 13, 2006 [cited July 27, 2008]; Available here: Is your desk making you sick?.
10. Schultz, M., et al., Bacterial contamination of computer keyboards in a teaching hospital. Infect Control Hosp Epidemiol, 2003. 24(4): p. 302-3.
11. Bures, S., et al., Computer keyboards and faucet handles as reservoirs of nosocomial pathogens in the intensive care unit. Am J Infect Control, 2000. 28(6): p. 465-71.
12. Rutala, W.A., et al., Bacterial contamination of keyboards: efficacy and functional impact of disinfectants. Infect Control Hosp Epidemiol, 2006. 27(4): p. 372-7.
13. Jones, S. Filthy as a loo seat: hazard of computer keyboards. The Guardian May 1, 2008 [cited July 27, 2008]; Available here: Filthy as a loo seat: hazard of computer keyboards.
14. Lankford, M.G., et al., Assessment of materials commonly utilized in health care: implications for bacterial survival and transmission. Am J Infect Control, 2006. 34(5): p. 258-63.
15. Barclay, L. Computer Keyboards Should Be Disinfected Daily. Medscape Medical News 2006 [cited July 21, 2008]; Available here: Computer Keyboards Should Be Disinfected Daily.
16. Kassem, II, V. Sigler, and M.A. Esseili, Public computer surfaces are reservoirs for methicillin-resistant staphylococci. Isme J, 2007. 1(3): p. 265-8.
17. Enriquez, C., N. Nwachuku, and C.P. Gerba, Direct exposure to animal enteric pathogens. Rev Environ Health, 2001. 16(2): p. 117-31.
18. International Organization for Standardization (ISO), Space environment (natural and artificial) — Process for determining solar irradiances. 2005. p. 8-9.
19. World Health Organization (WHO). Ultraviolet radiation. Ultraviolet radiation and the INTERSUN Programme 2008 [cited August 6, 2008]; Available here: Ultraviolet radiation.
20. World Health Organization (WHO). Health effects of UV radiation. Ultraviolet radiation and the INTERSUN Programme 2008 [cited August 6, 2008]; Available here: Health effects of UV radiation.
21. Ohnaka, T., [Health effects of ultraviolet radiation]. Ann Physiol Anthropol, 1993. 12(1): p. 1-10.
22. Sterile-Aire Protection: Frequently Asked Questions: What is UVV? 2007 [cited August 06. 2008]; Available here: Sterile-Aire Protection.
23. Tayloe, M., Germ warfare, in Fairfax County Times. 2007: Reston.

Product Fact Sheet

VirWall Keyboard Sanitizer

VirWall Keyboard Sanitizer KBS-1

Purpose of Product

To sanitize computer keyboards as a measure of preventing the spread of potentially pathogenic organisms

Reason for Development

Dr. John Roberts, inventor of the Keyboard Sanitizer, had never been as sick, as frequently, or for such long durations as when his son attended elementary school, a school with computer classrooms. In reading scientific journals to better understand how bacteria and viruses are transmitted, he learned that certain inanimate objects…

Principle of Action

Ultraviolet (UV) light causes molecular rearrangement of a microorganism’s DNA which prevents it from reproducing and therefore renders it microbiologically dead. The effectiveness of UV energy on microbial destruction is dependent upon intensity and time…