The current manuscript sheds light on the possible role of bioaerosols (from mouth breathing) that may serve as vectors for transmitting COVID-19 in asymptomatic carriers reporting to dental hospitals and, hence, may pose a great challenge for even a simple orthodontic diagnosis. Further, we would like to add a few preventive considerations for containment of this novel disease spread via bioaerosols emitted, particularly during mouth breathing.


Coronavirus disease (COVID-19) has posed great challenges presently and, in that, the role of healthcare professionals in preventing the spread of transmission is extremely significant. The novel disease has spread rapidly to several countries, affecting 223,022,538 people worldwide, causing 4,602,882 deaths on September 10, 2021, according to the reports of the WHO (World Health Organization, 2020)1. In view of this global pandemic that is quite alarming, WHO has stressed the importance of basic protective measures, mainly being hand hygiene and social distancing2.

Pre-symptomatic transmission of COVID 19

Recently, researchers reported that the novel coronavirus disease 2019 (COVID-19) spreads from asymptomatic carriers. The latest evidence suggests that pre-symptomatic transmission by viral shedding is quite possible, occurring just 2-3 days before the symptoms’ onset3, 4. Interestingly, the infectious profile of SARS-CoV-2 resembles more likely that of influenza rather than SARS4. At this stage, the exact mechanism by which the asymptomatic individuals acquire and spread the virus at the pre-symptomatic period is under exploratory research. We would like to emphasize our notable observations.

Pre-symptomatic transmission of COVID 19

Literature evidence suggests that any infectious material in a true aerosol form (i.e., < 50 μm diameter) becomes re-airborne as droplet nuclei that linger in the atmosphere for up to 30 minutes, thereby expanding the spatial extent of emitted particles5, 6. Apart from speaking/coughing, aerosols are also generated during normal breathing, commonly referred to as “exhaled bioaerosols” consisting of airway-lining fluid in small droplets7. Mouth breathing is another significant overlooked factor, producing the largest number of airborne droplets (< 1 µm) much more than breathing, speaking, and coughing, definitely posing a threat8. These emitted particles act as vectors for the spread of various infectious diseases, including influenza in the past and hence, we have to consider the impact of these bioaerosols on the current pandemic too. This could be one of the probable reasons that COVID-19 is highly transmissible between the subjects in the pre-symptomatic and/or asymptomatic stage3, 4.

Exhaled bioaerosols- a risk factor in orthodontic patients?

More recently, it has been reported that bioaerosols from mouth breathing serve as an under-recognized transmissible mode in SARS-CoV-2 infection9. This builds up internal pressure since we are at high exposure risk as health care professionals. The probability of risk transmission is quite high, especially in the case of mouth-breathing individuals who report with one or more significant orthodontic findings seeking treatment. Hence, the disease control measures for COVID-19 should be adjusted to account for probable substantial pre-symptomatic transmission, as stated earlier4. However, we would like to add considerations for containment of the spread via bioaerosols emitted, particularly during mouth breathing or normal breathing. More recently, Anfinrud et al. (2020) visualized speech-generated salivary droplets with and without masks by laser light scattering and qualitatively reported the significance of a damp cloth cover over the oral cavity to curb droplets emission10.

Suggested preventive measures

It was also reported in an earlier study by Edward et al.7 that nebulized suspension containing isotonic saline and surfactants like 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-94 palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) significantly reduced the exhaled aerosols by altering the physical properties of the lung-lining fluid, notably, surface tension and viscosity in “super spreaders” (i.e., high bioaerosol producers). Hence, this prophylactic inhalation measure can also be considered to combat COVID-19 transmission effectively via asymptomatic carriers, added to other defensive actions including isolation, enhanced personal hygiene, and use of face masks/shields as proposed. Further, filtering facepiece masks (FFP), especially FFP3 that possess a high filtration rate (99%), can be highly recommended amongst dentists to contain the airborne spread of the virus11, 12.


Therefore, it is understood that the generation of bioaerosols is an inevitable and never-ending process. Bioaerosols are omnipresent, and the exhaled bioparticles from asymptomatic COVID-19 carriers are a potential threat. The risk of transmission increases multifold, particularly in individuals with compromised immune systems due to debilitating diseases. Since there are no definite therapies available for the treatment of COVID-19 presently, it is indispensable to adopt the aforesaid prophylactic preventive actions carefully.



Author’s contributions

Conceptualization: B. Saravanakarthikeyan and Divya VC

Writing- Original Draft Preparation: Divya VC

Writing- Review & Editing: B. Saravanakarthikeyan

All authors read and approved the final manuscript.



Availability of data and materials

Not applicable.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.


  1. World Health Organization (WHO), Coronavirus Disease 19 (COVID-19) Situation Reports. https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports. Last accessed online on September 11 2021.. .
  2. World Health Organization (WHO), Coronavirus disease (COVID-19) advice for the public, Last updated March 18 2020, World Health Organization, Genewa, Switzerland, 2020. https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public.. .
  3. Bai Y., Yao L., Wei T., Tian F., Jin D.Y., Chen L., Presumed Asymptomatic Carrier Transmission of COVID-19. Journal of the American Medical Association. 2020; 323 (14) : 1406-7 .
    View Article    PubMed    Google Scholar 
  4. He X., Lau E.H., Wu P., Deng X., Wang J., Hao X., Temporal dynamics in viral shedding and transmissibility of COVID-19. Nature Medicine. 2020; 26 (5) : 672-5 .
    View Article    PubMed    Google Scholar 
  5. Hinds W.C., Aerosol technology: Properties, behavior, and measurement of airborne particlesWiley: New York (NY); 1982.
    Google Scholar 
  6. Harrel S.K., Molinari J., Aerosols and splatter in dentistry: a brief review of the literature and infection control implications. The Journal of the American Dental Association. 2004; 135 (4) : 429-37 .
    View Article    PubMed    Google Scholar 
  7. Edwards D.A., Man J.C., Brand P., Katstra J.P., Sommerer K., Stone H.A., Inhaling to mitigate exhaled bioaerosols. Proceedings of the National Academy of Sciences of the United States of America. 2004; 101 (50) : 17383-8 .
    View Article    PubMed    Google Scholar 
  8. Coulthard P., Dentistry and coronavirus (COVID-19) - moral decision-making. British Dental Journal. 2020; 228 (7) : 503-5 .
    View Article    PubMed    Google Scholar 
  9. S. Balasubramanian, D. Vinayachandran, Bioaerosols from mouth-breathing: Under-recognized transmissible mode in COVID-19?. Can Commun Dis Rep. 2021; 47 (56) : 276-278 .
    View Article    PubMed    Google Scholar 
  10. Anfinrud P., Stadnytskyi V., Bax C.E., Bax A., Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering. N Engl J Med. 2020; 2020 : 1-2 .
    View Article    PubMed    Google Scholar 
  11. Centers for Disease Control and Prevention (CDC). Strategies to Optimize PPE and 128 Equipment. 2020. Available at https://www.cdc.gov/coronavirus/2019- ncov/hcp/ppe-129 strategy/index.html (accessed April 2020). . .
  12. World Health Organization (WHO). Advice on the use of masks in the community, 131 during home care and in healthcare settings in the context of the novel coronavirus (COVID-19) outbreak. 2020. Available online at https://www.who.int/publications- detail/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in 134 healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak (accessed April 2020). . .