You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

Covid-19 pandemic, continues all over the world with the increasing number of confirmed cases and performed tests day by day. It has been shown that collecting nasopharyngeal samples, as the most commonly prefered method to perform RT-PCR, has disadvantages like causing discomfort and bleeding in patients. Sample collecting procedure also renders healthcare professionals by exposing them to the risk of transmission of the virus related to the direct contact with patients. These disadvantages make this procedure undesirable for the researchers and forces them to search for an alternative technique. At this point, saliva appears as an opportunity, regarding its high viral load. On the other hand, this high viral load poses a threat, especially for professions such as dental practitioners, with too much aerosol exposure. Since dentistry is a branch of health that constantly needs direct operations, it is necessary to be protected from the virus as much as possible while caring for the patient. A literature review was done using electronic databases "PubMed," "Google Scholar," and "Cochrane Database," on January 2021. Studies have proposed many different preventive measures in this regard. Therefore, the purpose of this review is to draw attention to the saliva by bringing together the recent research and also to provide information and a perspective to dental clinicians about both prevention and a potential diagnostic technique.
["Diagnosis", "Prevention"]