The novel coronavirus SARS-CoV-2 can also be found in saliva, according to a study carried out on 12 patients admitted in hospitals with laboratory-confirmed infection. Of the 12 patients, the virus was detected in the saliva of 11 patients. In one patient, shedding of the virus in saliva continued up to 11 days after hospitalisation.

The study carried out by researchers in Hong Kong and published in the journal Clinical Infectious Diseases has demonstrated the potential of using saliva as a non-invasive specimen for confirming infection and for viral load monitoring during the period of hospitalisation.

“The use of saliva is preferred over nasopharyngeal or oropharyngeal specimens because this would reduce the discomfort to the patient and reduce the health hazards to healthcare workers during repeated sampling,” the authors write.

The virus taken from the patients was also cultured in the lab. Three viral cultures tested positive for the virus, while two tested negative. This confirms that saliva contain live novel virus SARS-CoV-2.

Virus spread through saliva

The presence of live virus in saliva, as confirmed by positive culture, indicates that this body fluid may allow the spread of the virus. Besides direct or indirect contact, the SARS-CoV-2 virus can be transmitted through droplets.

“Saliva can be emitted through cough, and respiratory droplets containing influenza virus can be found even during normal breathing. Therefore, SARS-CoV-2 virus may be transmitted via saliva directly or indirectly even among patients without coughing or other respiratory symptoms,” the authors caution. 

Not only saliva secreted by salivary glands, the saliva specimens can also contain “secretions coming down from the nasopharynx, or coming up from the lung via the action of cilia lining the airway”. They are yet to study the source of the virus in the saliva samples.

The doctors collected saliva samples every day from six patients. The amount of virus present in the saliva — known as viral load — was highest in the earliest available samples in five patients. In one patient, the viral load was higher on the day after hospitalisation than the day of hospital admission.

“Our experience with SARS in 2003 showed that viral load often peaked at day 10 after symptom onset. Thus early detection and isolation of cases was strategic for infection control,” they write.