Microbes found on surfaces

Zhang, H. L. et al. 2022. SARS-CoV-2 RNA persists on surfaces following terminal disinfection of COVID-19 hospital isolation rooms.


  • To investigate if there were SARS-CoV-2 RNA on surfaces after terminal cleaning.
  • 51 patient rooms in 3 non-intensive care units were evaluated.
  • 48 (94.1 %) were sampled following and 3 (5.9 %) before ultraviolet germicidal irradiation (UVGI).

Terminal cleaning

  • Terminal cleaning was performed according to a checklist of surfaces.
  • Virex PlusTM disposable wipes, a quaternary ammonium product, were used for all surfaces within the room with the exception of the bathroom which were cleaned with ChloroxTM sodium hypochlorite disposable wipes.
  • One disposable wipe was used per surface.
  • Floors were cleaned with microfiber mops and BruTabsTM, a sodium dichloro-s-triazinetrione disinfectant.
  • Mops were to be used for a single patient room prior to disposal.
  • Cleaning began 45 minutes or later after patient discharge to allow for settling of infectious particles.
  • All rooms and bathrooms underwent ultraviolet germicidal irradiation (UVGI) after surface cleaning (Optimum-UVTM, Clorox Healthcare).
  • Monitoring of cleaning effectiveness was performed by manager inspection of 30 % or more discharge rooms.
  • While Adenosine triphosphate (ATP) monitoring is used in other units, visual monitoring was used primarily in COVID isolation rooms.
  • There were no periods during the study where shortage or availability of cleaning supplies altered cleaning practices.


  • SARS-CoV-2 RNA was detected on 193 per 602 (32.1%) surfaces after terminal cleaning
    • including 118 per 150 (78.7 %) floor surfaces
    • 58 per 252 (23.0 %) elevated high-touch surfaces
    • and 17 per 200 (8.5 %) elevated low-touch surfaces.
  • Compared to COVID-19 rooms during patient occupancy
    • terminally cleaned rooms had a lower prevalence of SARS-CoV-2 RNA contamination among elevated high-touch surfaces (58/252 [23.0 %] vs 272/830 [32.8 %])
    • but a similar prevalence among elevated low-touch surfaces (17/200 [8.5 %] vs 77/664 [11.6 %], P = .25) and floors.
  • The high prevalence of SARS-CoV-2 RNA contamination on terminally cleaned floors is of uncertain significance. Recent data suggest that hospital floors serve as an underappreciated source of pathogen dissemination via footwear, portable equipment, or contact with high-touch objects.

Tannhäuser, R. et al. 2022. Bacterial contamination of the smartphones of healthcare workers in a German tertiary-care hospital before and during the COVID-19 pandemic.


  • To investigate bacterial colonization on smartphones (SPs) owned by healthcare workers (HCWs) before (2012) and during the pandemic (2021).
  • Only the screens were investigated, not the back side of phones.


  • Devices underwent sampling under real-life conditions, without prior manipulation.
  • Isolates were identified by MALDI-TOF mass spectrometry and underwent microbiological susceptibility testing.


  • On 293 of 295 SP screens (99.3 %) bacterial contamination was present.
  • The most common bacteria found was coagulase-negative staphylococci (CNS = bacteria that commonly live on a person’s skin)
    • in 2012, 80 of 99 SPs (80.8 %), and
    • in 2021, 147 of 196 SPs (75 %)
  • The second largest group was spore forming aerobic bacteria
    • in 2012 (37 of 99, 37.4 %)
    • in 2021 (130 of 196, 66.3 %)
  • Polymicrobial contamination was detected
    • in 2012 on 54 of 99 SPs (54.5 %), and
    • in 2021 on 155 of 196 SPs (79.1 %)
  • Almost all bacteria detected can cause infections in critically ill patients, especially those with immunosuppression.
  • Methicillin-resistant S. aureus (MRSA) was not detected in 2012, but on 3 SPs (1.5 %) in 2021. Also, a higher rate of enterococci was detected on SPs in 2021 (35 out of 196, 17.8 %) compared to 2012 (3 out of 99, 3.3 %).
  • Cleaning the smartphone
    • in 2012 at least daily 23.2 %, when obviously contaminated 68.7 %, no cleaning 8.1 %.
    • in 2021 at least daily 45.9 %, when obviously contaminated 50,5 %, no cleaning 3.6 %.

Mody, L. et al. 2021. Environmental contamination with SARS-CoV-2 in nursing homes.


  • To investigate frequency and persistence of SARS-CoV-2 on surfaces.


  • Samples (2087 swabs) were taken (with 241 visits)
    • from rooms of 104 Covid-19 patients (total, 1896 samples): bed controls, call button, bedside tabletop, TV remote, privacy curtain, windowsill, toilet seat, doorknob, and air vent (if within reach)
    • from nearby common areas (191 samples): sitting area tabletop, sitting area chair or arm rest, dining room tabletop, nurses’ station tabletop, nurses’ station computer keyboard, and elevator buttons.
  • For all flat surfaces, an area of approximately 5 x 20 cm was swabbed. For smaller objects, the entire surface was swabbed.
  • 3-month study period.


  • SARS-CoV-2 positivity was 28.4 % (538/1896 swabs) on patient room surfaces and 3.7 % (7/191 swabs) on common area surfaces.
  • Nearly 90 % (93/104) of patients had SARS-CoV-2 contamination in their room at least once
  • TV remotes were most likely to be contaminated, with 68.1 % and the contamination was most persistent, often detected on both enrollment and during follow-up (34 %; 16/47).
  • Patients with greater independence are more likely than fully dependent patients to contaminate their immediate environment.

Abney, S.E. et al. 2021. Toilet hygiene—review and research needs.

Research results

  • The build-up of biofilm within a toilet bowl/urinal including sink can result in the persistence of pathogens and odours.
  • During flushing, pathogens can be ejected from the toilet bowl/urinal/sink and be transmitted by inhalation and contaminated fomites.
  • Use of automatic toilet bowl cleaners can reduce the number of microorganisms ejected during a flush.
  • Salmonella bacteria can colonize the underside of the rim of toilets and persist up to 50 days.
  • Pathogenic enteric bacteria appear in greater numbers in the biofilm found in toilets than in the water.
  • Source tracking of bacteria in homes has demonstrated that during cleaning enteric bacteria are transferred from the toilet to the bathroom sinks and that these same bacteria colonize cleaning tools used in the restroom.
  • Quantitative microbial risk assessment has shown that significant risks exist from both aerosols and fomites in restrooms.
  • Cleaning with soaps and detergents without the use of disinfectants in public restrooms may spread bacteria and viruses throughout the restroom.
  • The toilet bowl could potentially contain up to 1014 virus particles.

Aerosols produced by flush toilets

  • Significant aerosolization can occur resulting in potential transmission of pathogens by inhalation and via fomite contamination (Sars-CoV-2 also).
  • Large droplets settle out within a few minutes, smaller may persist and continued to settle out on surfaces for 90 min.
  • Residual levels of microorganisms may remain in the bowl after the initial flush, resulting in aerosolization of bacteria after repeated flushes.
  • In a seeded toilet experiment, Salmonella could be isolated from the air, the toilet seat and lid following flushing of the toilet. In bowl water Salmonella was found for 5 days and was isolated from the biofilm below the water line in the bowl for up to 50 days.

Surface fomite contamination

  • P. aeruginosa and E. coli as well as other Enterobacteria has frequently been found on sites such as the toilet seat and handle in addition to the toilet bowl.
  • Viruses can maybe persist on biofilms for long periods of time.
  • Several studies have reported the contamination of hospital patient toilets shared by patients. In South Africa found that 53–63 % of the restroom surfaces were contaminated with SARS-CoV-2. Highest amounts on the toilet seat and the cistern flush handle.
  • SARS-CoV-2 virus has been recovered from toilet seat, bathroom door handle and sinks in bathrooms housing patients with SARS-CoV-2 infections.

Impact of cleaning on spread of enteric pathogens in restrooms

  • A research made in US households showed that in seven of the eight homes with identified faecal coliforms, identical strains were isolated from either the toilet itself (toilet bowl, toilet seat bottom, flush handle) or the cleaning tool and at least two other surfaces (up to eight surfaces) in the bathroom (e.g., sink bowl, sink drain, sink countertop, sink faucet handle, shower/bath drain, shower/bath surface, floor 12 inches in front of the toilet).

Risk assessment of infections from restroom use

According to estimated Quantitative microbial risk assessment (QMRA) the risk of infection from SARS-CoV-2 from touching various surfaces in public restrooms

  • The greatest risk of infection (4.3 x 10-2 to 6.0 x 10-4) is when a person uses the toilet once in a day increasing to 1.0 x 10-1 to 1.4 x 10-3 if they used the toilet three times in a day.
  • Risks of infection for a one-time exposure are considered significant if less than 1 x 10-6.


  • Use of disinfectants is critical to preventing movement of enteric microorganisms throughout the restroom.
  • Colonization of biofilms and hard to clean area (the rim under the toilet) by pathogenic enteric bacteria such as Salmonella appear to be a problem.

Ding, Z. et al. 2020. Toilets dominate environmental detection of severe acute respiratory syndrome coronavirus 2 in a hospital.


107 surface samples were taken
• 37 from toilets
• 34 from other surfaces in isolation rooms, and
• 36 from other surfaces outside the isolation rooms in the hospital.


4 of these samples were positive
• 2 ward door handles,
• 1 bathroom toilet seat cover, and
• 1 bathroom door handle
Three were weakly positive
• 1 bathroom toilet seat
• 1 bathroom washbasin tap lever, and
• 1 bathroom ceiling exhaust louver.

Vasickova, P. et al. 2010. Issues Concerning Survival of Viruses on Surfaces.

According to the article, the survival of the virus on surfaces is affected by a combination of biological, physical, and chemical factors.

  • Anyhow, complete information regarding the influence of the environment on all viruses and their stability in external conditions does not exist.
  • Persistence of a virus in the environment is primarily affected by the presence of a viral envelope.

The article also states some data of viruses’ ability to spread infections.

  • A critical factor of viral transmission is its ability to survive in the environment.
  • Even if some viruses survive relatively poorly in the environment, the low infective dose suggests that these viruses are able to persist in sufficient numbers to act as a source of infection for several days, week or in some cases months.
  • Rapid spread of viral infections through contaminated surfaces is common particularly in crowded indoor establishments such as schools, day-care facilities, nursing homes, business offices, hospitals, or transport systems.
  • Nearly one thousand different types of viruses are known to infect humans, whilst the most common viral illnesses are produced by enteric and respiratory viruses.
  • It has been demonstrated that infective viral particles can survive on human hands and be transferred to animate and non-porous surfaces.
  • E.g., once the surface is contaminated, at least 14 persons could be contaminated or infected by touching a polluted door handle.
  • Successive transmission of virus from one person to another could be followed up to the sixth contact person.
  • Contaminated fingers could subsequently transfer a virus from up to seven clean surfaces.
  • Persistence of a virus in the environment is primarily affected by the presence of a viral envelope
    • Non-enveloped viruses (e.g., rotavirus, norovirus) have higher resistance to drying or desiccation methods and therefore are spread more easily than enveloped viruses (e.g., SARS-, influenza virus)
    • e.g., rotavirus can be infective on surfaces for at least 2 months
    • but respiratory viruses usually remain infectious for several hours to several days.
  • Variation in virus survival occurs within a viral family or even genus.
  • Effect of relative humidity (RH) and temperature varies within virus type.
  • Ultraviolet radiation is the crucial virucidal agent.
  • The majority of viruses remain viable for a longer period of time on non-porous materials, although there are exceptions.
  • The extent and state of virus adsorption on surfaces has an important influence on virus survival.
  • Data about the influence of other microorganisms on virus survival are contradictory.
    • Virus survival may increase or decrease with the number of microbes present on the surface.
    • Environmental isolates of bacteria with antiviral ability have been found.
    • Viruses can penetrate to biofilms and benefit from them.

Singh, D. et al. 2021. Viral load could be an important determinant for fomites-based transmission of viral infections.


  • To investigate viral pathogens on surfaces.


  • Viral samples were categorized using the cycle threshold (Ct) values
    • high (17 to < 24), moderate (24 to < 31), or mild (31 to < 38) viral load.
  • Samples were smeared on commonly used cardboard surface (absorbent surface) and stainless steel (non-absorbent surface).
  • After 90 min the samples were analysed.


  • Viral load/titter positively correlated with the viral material on surfaces.
  • Higher viral load (low Ct) samples exhibited higher probability of being detected on the surfaces than those samples with lower/moderate (high Ct) viral load.


  • Common inanimate surfaces are potential source of the viral transmission.
  • However, the viral load on these surfaces is key determinant of such transmission.