A. Upper respiratory tract disease is likely. Possibly rhinitis allergic or viral are very common. I would suggest to keep his nose and eventually eyes clean from discharge. Keep him indoors and eventually you can try to do some aerosol treatment. You can try that with boiled salted water left outside his carrier (while he is inside the carrier locked). Cover the carrier and the boiled water with a towel ( and lift it every 20-30 seconds).
Most of the times if the underlying cause is infective, antibiotics are needed though. So if the signs persist I would recommend to take him to your veterinarian.
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