Simplify the following text for a Grade 12 native English-speaking person.
Original: Diagnosis is made by seeing these symptoms ; having a history of exposure is also helpful but not always found , as kennel cough is easily spread through contact with contaminated surfaces such as the ground , toys , and sidewalks .
Simplified: Medical diagnosis is made by seeing these symptoms , having a history of exposure is also helpful but not always found as kennel cough is easily spread through contact with the ground , toys , sidewalks , dog parks .