Hanna Välimaa
MD, PhD, DDS, lecturer, consultant in Oral Microbiology and Infectious Diseases. Department of Virology, University of Helsinki and Department of Oral and Maxillofacial Surgery, Helsinki University Hospital, Helsinki, Finland
Tove Larsen
Associate professor, ph.d. Department of Odontology, Section of Clinical Oral Microbiology, University of Copenhagen, Denmark
Björn Klinge
Professor, odont dr, specialist in periodontology. Malmö University, Faculty of Odontology, Malmö, Sweden and Karolinska Institutet, Department of Dental Medicine, Huddinge, Sweden
Nils-Erik Fiehn
Associate professor emeritus, dr. et lic.odont. Department of Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Denmark
Headlines
COVID-19 pandemic has caused concern about SARS CoV-2 transmission risk in dental care
SARS-CoV-2 is often found in the saliva of the infected subjects
Oral epithelial cells and salivary glands are susceptible to SARS-CoV-2
More stringent infection control practices have been adopted to control risk of transmission
Almost two years have now passed since the new coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) started to spread globally from Wuhan, China, leading to coronavirus disease (COVID-19) pandemic. COVID-19 symptoms vary from mild respiratory and gastrointestinal symptoms to severe pneumonia, and even death. New mutated variants have emerged throughout the pandemic and caused concern about the new clinical features they may possess, regarding transmissibility, severity of disease and vaccine effectiveness.
SARS-CoV-2 is transmitted mainly by respiratory secretions. It is frequently found in saliva of both asymptomatic and symptomatic infected patients. This has created tremendous concern about transmission during dental care among dentists and patients. Consequently, access to non-urgent dental care was highly restricted in early phases of the pandemic. This has caused an overall debt in access to dental care and risked timely dental treatment.
Oral epithelial cells and salivary glands are susceptible to SARS-CoV-2. Still, so far, there is no evidence of any SARS-CoV-2 oral disease manifestation confirmed by virological diagnostics. Poorer oral health, in particular periodontitis, has been suggested to aggravate COVID-19 possibly via increased aspiration of oral bacteria causing coinfections or due to periodontitis associated systemic inflammatory state. Further studies are needed to elucidate the possible effects of SARS-CoV-2 virus on oral and systemic health.
COVID-19 pandemic has set dental health care to face unforeseen challenges on one hand in terms of restrictions for providing dental care and on the other giving treatment safely without knowing the real risks for viral transmission. Oral epithelium and salivary glands are targets for SARS-CoV-2 and the virus is a frequent finding in saliva of both asymptomatic and symptomatic infected individuals. This has mounted considerable concern both among patients and dentists. The purpose of this review is to give an update on SARS-CoV-2 and to elucidate its possible effects on oral health as well as to give an overview on the effects of the COVID-19 pandemic on dental health care.
SARS-CoV-2 and COVID-19
In December 2019, an outbreak of disease caused by a new coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurred in Wuhan, China [1]. The disease it causes was termed Coronavirus disease-19 or COVID-19. SARS-CoV-2 turned out to have a significant potential for severe disease and to be far more successful in transmission from person-to-person compared to the other two recently emerged new coronaviruses, namely SARS-CoV-1 in 2002 and MERS-CoV in 2009 [2]. Already on March 11 2020, the World Health Organization (WHO) declared the outbreak a global pandemic.
Coronaviruses, belonging to the family Coronaviridae, are enveloped viruses with a large positive-sense single-stranded RNA genome of about 27-32 kilobases. The genome encodes four structural proteins named envelope glycoprotein spike (S), envelope (E), membrane (M) and nucleocapsid (N) protein and several non-structural proteins. [2]
SARS-CoV-2 is the ninth coronavirus known to infect humans [1]. All previous coronaviruses infecting humans are zoonotic, i.e. their origin is derived from animals [1]. The origins of SARS-CoV-2 is still to be unrevealed, but bats have been suggested to be the natural reservoir and the pangolin the possible intermediate host transmitting infection to humans. SARS-CoV-2 has also been proposed to be a manipulated virus escaped from a laboratory. During the pandemic SARS-CoV-2 has undergone many mutations that have increased adaptation in humans which would argue against it being intentionally manipulated to infect humans. These mutations include improved spike protein receptor binding. Currently the strongest body of evidence suggests that SARS-CoV-2 has its origin in animals and has been accidentally introduced to human. [3]
Many variants of SARS-CoV-2 have emerged during the pandemic. Mutations occur frequently in viruses, especially RNA viruses. Most of the mutations are irrelevant but some may greatly impact the natural properties of the virus. SARS-CoV-2 variants differ from each other clinically in transmissibility, clinical symptoms, immune escape properties, susceptibility to vaccines and performance of diagnostic tests [4][5]. Based on these properties the variants have been classified as variants of concern (VOC), variants of interest (VOI) and variants under monitoring [6]. SARS-CoV-2 infections mounts antibodies against spike protein and nucleoprotein [5]. Of these, spike-specific antibodies neutralize the virus and provide protection against infection [5]. Therefore, current vaccines strategies mainly target the spike protein. Further, the mutations in spike protein have been shown to increase the infectivity and binding to cell surface receptor ACE2, the crucial initial step of infection [3]. The mutations in the spike protein region are of great interest and concern.
As of September 2020, the first VOC variants were identified. In addition to scientific nomenclature, VOC variants are designated by WHO with letters of the Greek alphabet. According to WHO, the VOCs currently include alpha (B.1.1.7), beta (B.1.351), gamma (P.1), delta (B.1.617.2) and omicron (B.1.1.529). To be defined as a VOCs, a lineage either shows increased transmissibility, changed epidemiology, increased virulence or change in clinical presentation or decreased effectiveness of public health and social measures or available diagnostics, vaccines and therapeutics. [6]
Pathogenesis
For the majority, COVID-19 has a relatively mild course in the form of fever, nasal discharge, sore throat, dry cough, headache, muscle ache, gastrointestinal symptoms and fatigue. Anosmia and ageusia may develop. More severe presentation of disease includes dyspnoea and pneumonia, and further sepsis syndrome and acute respiratory distress syndrom
