Epidemics, pandemics and dentistry: a commentary

Attempts to prevent infection and epidemics were rooted even before the postulate of ‘the germ theory of disease’ was proposed by Louis Pasteur in 1860s. For instance, in 1846, Semmelweis, a Hungarian physician, noted that the mortality from childbed fever among women in gynaecology wards in hospitals could be significantly reduced by the surgeons washing their hands in chlorinated lime solution before maternal contact.¹ Six years later, John Snow, a British physician, applied statistics and epidemiological approaches to determine and eradicate the source of a cholera outbreak in London. ² He traced the outbreak source to a contaminated water pump in Broad Street, London, UK, and from whence the concept of public health was born.²

Half a century earlier, in the late 1700s, one of the most profound events in medicine that have thus far saved virtually millions of lives globally occurred, also near London. That was the invention of the smallpox vaccines by Edward Jenner, much before the theory of asepsis was conceived by Joseph Lister at the Royal Infirmary in Glasgow, Scotland. Since then, vaccines and vaccinations have become integral to societal wellbeing and the prevention of global pandemics, COVID-19 being the most recent example, in this century.³

The following vignette is emblematic of the lengths to which humanity has gone to mitigate pandemics. In the same period as the vaccine invention, the smallpox contagion ravaged the world, including South America, where the Spanish empire was flourishing. The Spanish were then desperate to seek a method to transport the vaccine technology to the latter continent. In the absence of refrigerators and appropriate storage methods for the smallpox vaccine, a Spanish doctor, Francisco Xavier de Balmis y Berenguer, came up with an ingenious method to transport vaccine technology. His method was to ship ‘human incubators’ of the lowly virulent, cowpox virus (the basis of the smallpox vaccine), using a group of 22 orphan boys across the Atlantic on a ship called La Coruña bound for the Spanish colonies.⁴

Prior to embarkation, two to three boys were deliberately infected with cowpox by the doctor who sailed with the boys. When they developed pustules in mid-voyage, the doctor took the lymph from the infected boys to inoculate two more. The process was repeated until the ship arrived a few months later in South America. Xavier’s expedition is considered the first international vaccination campaign in history, and one of the most critical events in the history of medicine.⁵

As seen from the beguiling story above, epidemics and pandemics have significantly impacted human societal behaviour over the millennia. Smallpox was one of the major pandemics that annihilated millions in the late 1700s, but before that, humans have weathered many such pandemics, some deadlier than others. Indeed, the oldest recorded pandemic goes back to the early stages of the Chinese Empire circa 240 BC, and one of the most devastating that killed over 100 million people is thought to be the influenza pandemic of 1918.⁶

A number of theories have been proposed for the origins of pandemics and epidemics among humans, particularly those that originated through animal–human contact, as in coronavirus infections. The most plausible is as follows. Historically, when humans were village-dwelling, hunter-gatherers within a limited locale, lacking means of transport, pandemics were limited to focal population groups. This led to either the annihilation of the small group, succumbing to the disease, or alternatively, the few survivors acquiring immunity and overcoming the infectious agents, and the ‘fittest surviving’. However, there was a fundamental departure in such population dynamics when humans started domesticating animals, farming, food storage and leading a relatively sedentary lifestyle in larger populations. Such a communal, agrarian society with human and animal co-socialization in close proximity led to the zoonotic diseases, such as COVID-19, which we witness today.⁶

Animals and humans co-socialize even in the present day in rural China, with many sharing the same premises. There is also consumption by humans of wild and domesticated animals, such as civet cats, pangolins, dogs and cats. Despite the best efforts and the recent campaigns of the Chinese government to stop these habits, including selling live-wild animals in markets, the practice continues. In this context, it has been estimated that animals are accountable for more than 60% of the known communicable diseases affecting humans today.⁷

‘One World One Health’ concept and dentistry

Apart from the human–animal co-socialization, which is highly likely to be the modus operandi of pathogenic animal viruses crossing the so-called ‘species barrier’ and initiating human pandemics, what are the other reasons for the origins of the deadly diseases, and why they recur at a regular pace? These questions were posed to an erudite group of academics convened by the US National Institutes of Health a few decades ago,⁸ and their findings are as highly relevant today as they were then. The report of the latter commission cited the following as the root causes for the emergence of deadly epidemics and pandemics.

• Healthcare: new medical devices, organ/tissue transplantation, immunosuppression, antibiotic abuse and contaminated blood and blood products
• Human behaviour: increasing sexual promiscuity, injectable drug abuse;
• Environmental changes: deforestation, drought, floods and global warming
• Microbial adaptation: the emergence of new species from the wild (eg COVID-19, HIV), changes in virulence and toxin production and development of antibiotic resistance.

Fast forward to today, and these findings, have been aptly articulated in the very recent ‘One World, One Health’ concept promulgated by the Centres for Disease Control and Prevention. They define this concept as a ‘collective, multi-sectoral, and trans-disciplinary approach – working at the local, regional, national, and global levels – to attain ideal health upshots recognizing the interconnectedness between people, animals, plants, and their shared environment.’^9,10

In simple terms, this strategic approach addresses several global health challenges by improving human, animal, and environmental health to mitigate the adverse effects of current and future epidemics and pandemics. Moreover, such an approach, with shared connectivity between humans, animals and the environment, should protect all three domains (Figure 1).

The ‘One health’ approach cuts across all ecological and health boundaries. It serves as a reminder that dental professionals advocating for oral health and general health need to be active participants, engaging in education, research and promotion of this concept for the overall benefit of humanity. While this is an additional advocacy approach for the profession to mitigate the emergence of new communicable diseases, it is instructive to see how our professional behavioural practices, particularly the applied infection control measures, have been impacted by past pandemics and epidemics.

Pandemics and dental practice

Some of the earliest nascent steps, such as disinfection and vaccination, are described above, leading to the contemporary infection control measures applied in medicine and dentistry. However, it is salutary to recognize the developmental steps that led to the extensive infection control regimentation of dentistry we practice today, and how these were moulded by past epidemics and pandemics (Figure 2).

Although the ‘germ theory’ has long been considered proven, in the late 1700s, through the collective efforts of Louis Pasteur, Joseph Lister and Robert Koch, its implications for surgical practice were not immediately apparent. Unwashed, bloodstained surgical attire was re-used in operating rooms even in the late 1870s, and surgeons operated without masks or head coverings as late as the 1880s. This all changed in 1889 when Dr William Halsted wanted to help his nurse, Caroline Hampton, who suffered from contact dermatitis, use the first pair of rubber gloves in a hospital.¹¹

Despite these developments in medicine, the routine wearing of gloves was not the norm in dentistry until half a century later, in the late 1950s. The profession in most countries paid only lip service to infection control and personal protection equipment (PPE) and brazenly flouted such guidelines even if they existed in various jurisdictions.¹² However, a tipping point for the mandated glove wear in dentistry was the reports in early 1980s of several oral and dental surgeons transmitting hepatitis B infection to some of their patients in the US and the UK and the concomitant adverse publicity in the media.^13,14

Subsequently, another viral pandemic, still widely prevalent, the HIV disease, brought the gaps in infection control measures in dentistry into sharp focus when a patient in Florida, USA, Kimberly Bergalis, claimed that she (and subsequently six others) acquired the infection from her dental surgeon, Dr David Acer, when she attended for dental treatment. However, after protracted inquiry, the possibility of HIV transmission from the surgeon to the patient in the dental operatory has been ruled out,¹⁵ but not before the reputational harm to the profession reverberated throughout the world.

The so-called ‘Florida Dentist’ case showed up the crucial importance of infection control in dentistry and led to its further reinforcement in many regions. Furthermore, the realization that asymptomatic HIV-infected individuals and hepatitis B carriers could be clinic attendees led to the emergence of another important infection control principle, the need to identify that all patients attending dental practice, irrespective of their health status, could be infectious. Hence the necessity of all patients to be treated under blood and body fluid precautions. Since then, and being cognisant of diseases such as hepatitis C and multi-drug resistant tuberculosis and Staphylococcus aureus infections posing a threat to healthcare workers, the health authorities in the US and UK have issued a string of guidelines on infection control in dental settings.¹⁶ The formal promulgation of infection control guidelines for medical and dental practices entitled ‘universal precautions’ in response to the HIV pandemic occurred in 1985.^17,18

In the late 1980s, the CDC announced an enhanced advisory termed ‘standard precautions’ to reduce the spread of bloodborne and other pathogens in hospitals and clinics. The latter recommendations were followed by supplementary, additional ‘transmission-based precautions’ to mitigate the risk of the droplets, aerosol and contact transmission of airborne and other virulent infections such as tuberculosis and vancomycin-resistant S aureus (VRSA) infections.¹⁶ These guidelines are currently applied in dentistry during the post-pandemic period owing to the high probability of aerosol transmission of SARS-CoV-2 and the very high infectivity of variants, such as the Omicron and its descendants. In addition, a revised set of recommendations for vaccines for dental healthcare workers is also in force owing to COVID-19.¹⁹ However, it is, as yet, unclear how long these strict infection protocols must be sustained in the face of an abating pandemic.

These unremitting, regularly occurring pandemics and epidemics have fundamentally modified how we practise dentistry today. Some of the major features of dental practice likely to irretrievably change our profession during the post-pandemic period and into the foreseeable future, are briefly discussed below (Figure 3). These include:

• Vaccine and vaccinations;
• Point of care (POC) diagnostics;
• Teledentistry;
• Reinforced infection control, including transmission-based precautions;
• Pedagogy and continuing professional education.

Vaccines and vaccinations

The unprecedentedly rapid development of the first successful mRNA vaccine for COVID-19 within a record-short period of 9 months from the advent of the disease was a testament to human ingenuity and technological prowess.²⁰ Over nine major COVID-19 vaccines are currently produced through various vaccine platforms and available to the public.^21,22 Thanks to these vaccines that have been the mainstay of our battle against the pandemic, we have witnessed a slow, yet certain, abeyance of the disease in almost all regions of the world. Indeed, the current milder waves of COVID-19 in some jurisdictions are called the ‘pandemic of the unvaccinated’, implying the extremely high efficacy of the new COVID-19 vaccines. Vaccine hesitancy of a significant proportion of the populace, both in the developed and developing world, appear to be the major factor behind this issue.²³ As vaccination of over 70% of the global population has been achieved,²⁴ it is likely that a global state of ‘herd immunity’ has been realized, but it remains to be proven in the fullness of time. Herd immunity, though, is not a justification for curbing COVID-19 vaccination, and the current thinking is that all clinical professionals must be successfully vaccinated against the disease to sustain their immune status.

Unfortunately, the list of vaccines mandated for dental healthcare workers, ranging from hepatitis B to seasonal influenza, keeps lengthening.²⁵ This said, the need for periodic booster COVID-19 vaccine owing to the emergence of new viral variants and/or the temporal waning of the antibody levels is still debated in the absence of appropriate post-vaccine immune correlates.

Point of care (POC) diagnostic tests

The evolutionary demographics and the endemicity of COVID-19 in various geographic regions are still uncertain. At the time of writing (25^th March 2023), WHO reports a total daily global tally approaching 33,000 cases.²⁴ These cases are mainly seen in developing countries with relatively low vaccine uptake.

In the face of this scenario, it has been proposed that the profession adopt the rapid, point-of-care (POC) diagnostic tests for SARS-CoV-2 antigens/antibodies for all clinic attendees immediately before treatment. However, the extent to which such POC diagnostics are conducted has not been mandated and is likely to be dictated by the disease prevalence in a specific jurisdiction.

The currently marketed POC tests are robust, reliable, sensitive, specific and available as inexpensive kits to aid easy administration by any dental team member.²⁶ They are essentially based on molecular techniques, such as polymerase chain reaction (PCR), lateral flow and loop-mediated isothermal amplification (LAMP) technology.²⁷ However, newer, next-generation technologies based on biorecognition, such as electrochemical sensors, field-effect transistor (FET)-based biosensors, immunosensors, magnetic biosensors, enzyme-based sensors, and DNA biosensors based on salivary analysis, are in the pipeline. Indeed biosensors have already been evaluated for detecting infectious diseases such as influenza.²⁸

Finally, many unanswered issues need to be resolved regarding the practicality of managing POC diagnostic tests as an element of a structured screening programme in dentistry, such as the frequency of testing, and patients’ right to be tested. A continuing dialogue between the medical and dental professions is required to elicit responses to these.

Teledentistry

Minimizing physical contact with patients is critical to curbing any infectious disease. Teledentistry is a useful but little-used tool for health professionals to achieve this aim. It is defined as ‘the remote facilitating of dental treatment, guidance, and education via information technology instead of direct face-to-face contact with patients’.²⁹ The four significant components of teledentistry are teleconsultation, telediagnosis, teletriage and telemonitoring, each of which has essential functions applicable to dental practice.

It is perhaps correct to state that teledentistry came of age during the height of the COVID-19 pandemic. Many jurisdictions used the tool for remote consultation for patients with acute infections and those in quarantine or during the post-recovery period, as well as for follow-up advice and assessment.³⁰ Additionally, the value of teledentistry came into focus during quarantine periods for continuing care for pre-existing oral diseases, such as oral cancer rehabilitation and malignant or other suspect oral lesions.³¹ Several countries, such as Indonesia and Thailand, where their vast populace is thinly dispersed in many remote regions and islands, appear to be quickly embarking and grasping this technology, realizing its utility for the clinician and the patient.³²

Nevertheless, there are significant challenges facing teledentistry as a management tool because of its novelty, and the technological barriers and the poor acceptance by patients who may be unwilling to part with their traditional consultation methods.³³ Nevertheless, the current explosive growth in mass media technology, such as cloud-based data services, artificial intelligence (AI) and big data resolution through bioinformatics, together with the mass ownership of various inexpensive yet reliable communication devices, should popularize teledentistry in the not-too-distant future.³⁴

Reinforced infection control, including transmission-based precautions

Aerosol generation is a manifest product of clinical dentistry. Although the profession was well aware of this danger, and many steps have been taken in the past through administrative and engineering control measures, the hitherto unknown insidious and ferocious manner in which SARS-CoV-2 spreads through aerosols and entrained air particles was another wake-up call for dentistry to further augment these infection control measures. The latter feature of a highly virulent virus impacted not only our societal behaviour, being quarantined for months, sometimes years on end, but also clinic architecture and airflow design.

The profession has to pay heed to this fact, now and into the future, being mindful of the need for dental operatory redesign or their retrofitting for good ventilation and engineering controls. Furthermore, educational and similar establishments need to invest in newer, more efficacious airflow technologies in the face of the current and possible future epidemics and pandemics. Such provisions for the reduction of infectious bioaerosols include: (i) extra-oral high-volume evacuation; (ii) negative pressure ventilation; (iii) enhanced efficacious air filtration; (iv) ultraviolet irradiation of the dental operatories during fallow periods; and (v) transparent barriers in patient–administrator communication portals.³⁵

Pedagogy and continuing professional education

The COVID-19 pandemic also impacted dental pedagogy and how we learn the craft of dentistry in varied ways.³⁶ These included administrative controls, such as virtual lectures or group tutorials, developments in haptics-based technology and remote operative dentistry and training protocols, as well as the use of visuals, such as Zoom technology. There is little doubt the newer technologies are here to stay, long past the pandemic, due to their efficacy, simplicity and accessibility.

Continuing education norms were also challenged because of the pandemic with the realization that physical lecture attendance is not a prerequisite for learning, and assessments and examinations could be reliably and effectively conducted remotely, saving travel time and associated accommodation expenses.

Last, but not the least, the expansion of the repertoire of the dental practice beyond the traditional boundaries was another aspect upon which the COVID-19 pandemic impinged. The realization that dental professionals are well placed to join public health initiatives and hence, need to be empowered to be advocates of patients’ immunization (including influenza, HPV and childhood vaccination schemes) and used as vaccinators in pandemic periods were significant issues in this context. Should we now take this cue and broaden the dental curriculum through interprofessional education systems and extend dentistry beyond just dental/oral care?^35,37

Future perspectives

It is correct to say that the dental profession was a few steps ahead in grappling with the pandemic because of the lessons learned in the past through previous epidemics and pandemics. When the COVID-19 pandemic arrived, we already had an array of infection control measures in place. This was evident in the small number of dental personnel who succumbed to the infection, despite the warnings of some authorities at the beginning of the pandemic that dental professionals were the most vulnerable among healthcare professionals to COVID-19 infection due to the aerosols generated in the clinic environs. Yet, we cannot rest on our laurels and should be forearmed, not only for an endemic infection and future flareups with various SARS-CoV-2 variants, but also to face new emerging infectious threats that are predicted to arrive periodically.

There is a silver lining in this grey cloud as technological advances and predictive AI technology are likely to forecast the next great pandemic. One such approach, ‘deep-mutational scanning’, examines surface-antigen ‘drifts and shifts’ of the pathogens in silico using AI and machine learning tools.³⁸ This means that vaccines for the impending viral variants or, indeed, a new pathogen could be predicted far in advance and a new infection could be nipped in the bud prior to becoming a ravaging pandemic.