COVID 19: A Salivary Perspective

An emergent pneumonia outbreak originated in Wuhan City, in the late December 2019. The pneumonia infection has rapidly spread from Wuhan to most other provinces and other 24 countries . World Health Organization declared a public health emergency of international concern over this global pneumonia outbreak on 30th January 2020.

The typical clinical symptoms of the patients who suffered from the novel viral pneumonia were fever, cough, and myalgia or fatigue with abnormal chest CT, and the less common symptoms were sputum production, headache, hemoptysis, and diarrhea. This new infectious agent is more likely to affect older males to

cause severe respiratory diseases. Some of the clinical symptoms were different from the severe acute respiratory syndrome (SARS) caused by SARS corona virus (SARS-CoV) thathappened in 2002–2003, indicating that a new person-to-person

transmission infectious agent has caused this emergent viral pneumonia outbreak. Chinese researchers have quickly isolated a new virus from the patient and sequenced its genome (29,903 nucleotides). The infectious agent of this viral pneumonia happening in Wuhan was finally identified as a novel

corona virus (2019-nCOV), the seventh member of the family of corona viruses that infect humans. On 11th February 2020, WHO named the novel viral pneumonia as “Corona Virus Disease (COVID19)”, while the international Committee on Taxonomy of Viruses (ICTV) suggested this novel corona virus name as “SARSCoV-2” due to the phylogenetic and taxonomic analysis of this novel corona virus

A Novel Corona virus (COVID-19) is associated with human to-human transmission via droplet and feaces .The COVID-19 is identified in saliva of infected patients.

Considering it the COVID-19 outbreak is a reminder that dental/oral and other health professionals must always be diligent in protecting against the spread of infectious disease, and it provides a chance to determine if a non-invasive saliva diagnostic for COVID-19 could assist in detecting such viruses and reducing the spread. The COVID-19 transmission via contact with droplets and aerosols generated during dental clinical procedures is expected. There is a need to increase investigations to the detection of COVID-19 in oral fluids and its impact on the transmission of this virus, which is crucial to improve effective strategies for prevention, especially for dentists and healthcare professionals that perform aerosol-generating procedures. Saliva can have a pivotal role in the human-to-human transmission, and non-invasive salivary diagnostics may provide a convenient and cost-effective point-of-care platform for the fast and early detection of COVID-19 infection.

The present outbreak of the 2019 corona virus strain (COVID-19) constitutes a public health emergency of global concern. International centers for disease control and prevention are monitoring this infectious disease outbreak; symptoms of

COVID-19 infection  include fever, cough, and acute respiratory disease, with severe cases leading to pneumonia, kidney failure, and even death. Currently, the available COVID-19 genome sequences from clinical samples suggest that this viral emergence is related to bat corona viruses . Although the corona virus infection in humans frequently presents with mild severity, the beta corona virus infection of either the severe acute respiratory syndrome corona virus (SARS-CoV) or the Middle East respiratory syndrome corona virus (MERS-CoV) resulted in higher mortality rates . Given the novelty of COVID-19, some characteristics of the virus remain yet unknown.

The Chinese Centre for Disease Control and Prevention isolated the COVID-19. It published the viral genome sequence data immediately in international database banks Gen Bank and the Global Initiative on Sharing All Influenza Data (GISAID)

This action enabled laboratories in several countries to develop unique PCR tests focusing on the diagnosis of COVID-19. Currently, the COVID-19 transmission routes are still to be determined, but human-to-human transmission has been confirmed The laboratory diagnostic tests should be performed using nasopharyngeal, Oro pharyngeal, and blood samples. Expectorated sputum and other specimens in severe respiratory disease should be considered as lower respiratory tract samples. Several potential scenarios of COVID-19 transmission have been described. The transmission via contact with droplets from talking, coughing, sneezing (related to human respiratory activities), and aerosols generated during clinical procedures is expected, as it would be for other respiratory

infections. The origin of droplets can be Nasopharyngeal or Oropharyngeal,

normally associated with saliva. Larger droplets could contribute to viral transmission to subjects nearby, and, on the other side, the long-distance transmission is possible with smaller droplets infected with air-suspended viral particles .

Considering that laboratory diagnostic tests are also performed in

blood samples, the transmission by contaminated blood should also be considered. In this context, healthcare workers, such as dentists, may be unknowingly providing direct care for infected, but not yet diagnosed COVID-19 patients, or those considered to be suspected cases for surveillance. Asymptomatic infections seem to be possible and transmission may occur before the disease symptoms appear. A recent clinical study indicates that 29% of 138 hospitalized patients with COVID-19-infected pneumonia in Wuhan, China, are healthcare workers

As in Bronchoscopy , inhalation of airborne particles and aerosols produced during dental procedures on patients with COVID-19 can be a high-risk procedure in which dentists are directly and closely exposed to this virus. Therefore, it is crucial for dentists to refine preventive strategies to avoid the COVID-19

Infection  by focusing on patient placement, hand hygiene, all personal protective equipment (PPE), and caution in performing aerosol-generating procedures. The Interim Guidance for Healthcare Professionals from CDC has been updated, and it is subject to change as additional information on COVID-19 infection and transmission becomes available. Diagnosis of COVID-19 can be performed using salivary diagnosis platform. Virus strains have been detected in saliva as long as 29 days after infection, indicating that a non-invasive platform to rapidly differentiate the biomarkers using saliva could enhance disease detection. Saliva samples could be collected in patients who present with Oropharyngeal secretions as a symptom Bearing in mind the requirement of a close contact between healthcare workers and infected patients to collect Nasopharyngeal or Oropharyngeal samples, the possibility of a saliva self-collection can strongly reduce the risk of COVID-19transmission. Besides, the nasopharyngeal and Oropharyngeal collection promotes discomfort and may promote bleeding especially in infected patients with thrombocytopenia. The sputum of a lower respiratory tract was produced by only28% of COVID-19 patients, which indicates a strong limitation as specimen to diagnostic evaluation There are three different pathways for COVID-19to present in saliva:

1) In the lower and upper respiratory tract that enters the oral cavity together with the liquid droplets frequently exchanged by these organs.

2) Present in the blood can access the mouth via Crevicular fluid, an oral cavity-specific exudate that contains local proteins derived from extracellular matrix and serum-derived proteins .

3) To occur in the oral cavity is by major- and minor-salivary gland infection, with subsequent release of particles in saliva via salivary ducts. It is essential to point out that salivary gland epithelial cells can be infected by SARS-CoV a short time after infection in rhesus macaques, suggesting that salivary gland cells could be a pivotal source of this virus in saliva .

Additionally, the production of SARS-CoV-specific secretory immunoglobulin A (sIgA) in the saliva of animal models intranasally immunized was previously shown Considering the similarity of both strains, we speculate that salivary diagnosis of COVID-19 could also be performed using specific antibodies to this virus.

Further studies are needed to investigate the potential diagnostic of COVID-19 in saliva and its impact on transmission of this virus, which is crucial to improve effective strategies for prevention, especially for dentists and healthcare professionals that performaerosol-generating procedures. Saliva can have a pivotal role in the human-to-human transmission, and salivary diagnostics may provide a convenient and cost effective point-of-care platform for COVID-19 infection.

Author: Dr Sachidanand Mallya P

A B Shetty Memorial Institute Of Dental Sciences, Mangalore, Karnataka, India