I belive you are refering to Calicivirus which has upper respiratory symptoms:
'Feline Upper Respiratory Disease Complex' is the term used to describe a condition affecting the mouth, nasal passages, sinuses, and upper airway in cats and kittens. There are multiple causes of feline upper respiratory complex, but 80-90% of the cases are caused by feline herpes-1 (also called feline rhinotracheitis virus) and calicivirus (pronounced cal-ee-chee). Other causes include Chlamydophila felisi (previously termed Chlamydia), feline reovirus, Bordetella bronchiseptica, Pasteurella spp., and mycoplasmas. Infections and symptoms by some of these agents may occur secondarily to an infection with rhinotracheitis virus or calicivirus.
Protection is in the FVRCP vaccine. This virus is treated successfully with antibiotics.
I hope your boy will be fine.
Sincerest best wishes,