A comparison of oral and intranasal inoculation in SARS-CoV-2
Studies with Syrian golden hamsters have shown that SARS-CoV-2 virus can cause mild pneumonia with very mild, mild to sub-threshold clinical signs by oral introduction of the pathogens, which is less severe compared to intranasal inoculation. In contrast, viral shedding from the oral cavity continues for the same length of time as in intranasally infected hamsters.
Clinical studies were performed to compare the difference in symptoms between Syrian hamsters infected orally and intranasally with SARS-CoV-2. This yielded results suggesting a clear differentiation between the two inoculations.
In the respiratory tract and lungs, oral inoculation showed a low viral load and mild inflammatory symptoms. Whereas intranasal inoculation showed high viral load and severe inflammation.
In the case of oral inoculation, the small intestine showed a low viral load and hardly any inflammatory symptoms. In contrast, intranasal inoculation showed a high viral load and severe inflammation.
During oral inoculation, the test animals showed no weight loss or other signs of disease. In contrast, signs of disease and loss of body weight were observed in the animals given the intranasal inoculation.
Both oral and intranasal inoculations had comparable viral shedding in the oral region and excretions.
As a conclusion, infection via the nose causes a more severe course of disease with more severe symptoms than oral infection.
Source: Cell Reports Medicine 1, 100121, October 20, 2020