Which of the following would NOT be a symptom of an upper respiratory infection?

Conjunctivitis, also known as pink eye, typically involves inflammation of the outer membrane of the eyeball and the inner eyelid. While it can sometimes occur alongside upper respiratory infections due to viral infections like adeno-virus or certain types of respiratory infections that can lead to complications affecting the eyes, it is not a direct symptom of upper respiratory infections such as the common cold or flu. Instead, upper respiratory infections more commonly present with symptoms like cough, fever, and tachypnea, which are directly related to the respiratory system.

On the other hand, a cough is frequently associated with upper respiratory infections as a result of irritation in the throat and airways, while a fever greater than 39°C indicates the body's response to infection, and tachypnea reflects an increase in respiratory rate that can occur due to infection and inflammation in the respiratory system. These options are typical signs of upper respiratory infections, making conjunctivitis the outlier in this context.