It's not as though anyone likes having the flu, but there's not usually all that much that can be done about it, other than the standard approach of getting plenty of rest and staying hydrated, with antibiotics sometimes playing a role in treatment too. The same can be said for your cat—when they get the flu, it's unlikely to be serious. However, cat flu can sometimes develop into something far more dangerous, so it's important to know the signs.
Cat flu is in fact a blanket term for a lingering respiratory illness caused by your cat becoming infected by a pathogen (typically calicivirus or feline herpes virus). It causes the symptoms you might expect, such as lethargy, sneezing and coughing, and this might be the extent of it, with your cat's immune system overcoming the illness without the need for intervention.
More Serious Indicators
Intervention can become necessary when your cat's immune system is showing signs of being overwhelmed. This is indicated by the presence of dribbling, a runny nose, and often an escalation of coughing and sneezing. Your cat might appear to be in pain, as sore muscles and tendons combined with a fever make movement difficult. Your cat's eyes can also become runny (conjunctivitis) and they can become unwilling to eat, which suggests the presence of mouth ulcers and a sore throat. If your cat begins to display these symptoms, it's important to transport them to your nearest animal health services provider without delay.
Managing the Flu
Veterinary treatment will take into account the severity of your cat's response to the flu. Antibiotics are likely to be prescribed, and in the case of healthy adult cats, no further action might be necessary, other than basic nursing care at home (such as regularly wiping away discharges from their eyes, nose, and mouth). For kittens and older cats, or adults with a compromised immune system, antibiotics may be used in conjunction with intravenous hydration. In extreme cases, when mouth ulcers and a sore throat has led to an ongoing refusal to eat, a temporary feeding tube might be used.
Once your cat has been affected by cat flu, they can be a carrier with an occasional recurrence of symptoms. This varies a considerable amount, and some cats might be facing another bout of the flu at some point in their lifetime, whereas other cats may not display further symptoms despite being a carrier. Talk to your vet, and ensure that your cat's vaccinations are up to date.
Just like in humans, cat flu can range from mild to dangerous, so it's important to know when action is needed.