We have just discovered that our cat has calicivirus. He is doing much better, but he has lost his voice. He attempts to meow but no sound comes out. Will his voice eventually return?
It sounds like due to the calicivirus he has now got laryngitis which is just inflammation of his larynx treating the underlying condition and once the inflammation goes away his meow should come back. It is fairly common.
I would go ahead and call your vet and discuss this with them as I am not a vet and I dont know if they can give him anything to help or if it just has to heal on its own.
If your cat was treated with antibiotics for a possible, or confirmed, secondary bacterial infection, he may either need a longer duration of the antibiotic, or more time to pass for full recovery, depending on the timing of his voice loss and the antibiotics. If he did not get an antibiotic, he might need one. So, yes, tell your vet what is going on.
Watch for signs of unwillingness to eat or drink much, as that might indicate pain/discomfort when swallowing. If the laryngeal area is swollen, the vet may want to give him an anti-inflammatory. I would suspect his voice will return eventually.