Upper Respiratory Infection in Cats 🐱😷

By Dr Duncan Houston, BVSc

Feline upper respiratory infections (URIs) are among the most common illnesses seen in cats, especially in kittens or shelter environments. While most resolve on their own, some cases require medical care. In this 2025 veterinary guide, I break down the signs, causes, treatments, and vaccine options for feline URIs. 💉

🧪 What Causes URIs in Cats?

The top culprits are:

• 🐱 Feline herpesvirus (FHV-1) – causes lifelong infection with flare-ups triggered by stress
• 🐱 Feline calicivirus (FCV) – more likely to cause oral ulcers, joint pain, and lingering shedding
• 🦠 Chlamydophila felis
• 🦠 Mycoplasma and Bordetella

Herpes and calici cause 90% of cases. Neither can infect humans. 🧬

🤧 Common Signs of URI

• 🌡️ Sneezing and fever
• 👃 Nasal discharge
• 👁️ Runny eyes
• 🤢 Cough or mouth ulcers
• 🔇 Hoarse voice or “sniffles”
• 🐾 Loss of appetite (if severe)

Kittens may experience severe symptoms, especially if not eating or becoming dehydrated from nasal discharge. 🚨

⚠️ What Cats Are at Risk?

• 😿 Shelter or rescue cats
• 🏠 Multi-cat households
• 🐾 Outdoor cats or strays
• 😺 Persian or flat-faced breeds

Most kittens are exposed early. Stress—like surgery, a new pet, or boarding—can trigger herpes flare-ups for life. 😿

🧬 Infection Timeline

Symptoms appear 2–5 days after exposure. Most viral colds last 7–10 days. Herpes remains dormant but can reactivate during stress. Calicivirus shedding may last months or even life-long. 🧪

🏥 When to See a Vet

Call your vet if you notice:

• ❌ Loss of appetite
• 🌬️ Open-mouth breathing or labored breathing
• 🔥 Lethargy or high fever
• 🩺 Oral ulcers or eye ulcers
• 😿 Thick nasal discharge

💊 How Is It Treated?

Treatment depends on the severity:

• 💧 Fluids for hydration (oral, IV, or under the skin)
• 💊 Antibiotics (like doxycycline) if bacterial co-infections suspected
• 👁️ Eye ointments for conjunctivitis
• 🛏️ Hospitalization for severe cases or kittens not eating

Antivirals: Famciclovir may be used for herpes, and Polyprenyl Immunostimulant is USDA-approved for chronic herpes. 💉

🧴 Special Therapies

• 💊 N-acetylcysteine – oral mucolytic to break down mucus
• 🧼 Nasal flushing under anesthesia for chronic congestion
• 🥣 Assisted feeding and warm steam therapy

💉 Vaccination Options

Vaccines reduce symptom severity but do not prevent infection. Choose:

• 💉 Injectable vaccines (3-in-1 or 4-in-1 with Chlamydophila)
• 💉 Nasal vaccines – faster immunity (3–4 days), especially helpful during outbreaks

The AAFP recommends the 3-in-1 combo. Vaccines for calici, herpes, and distemper are considered core. 💉

🧬 Hemorrhagic Calicivirus

This rare but severe strain causes bleeding, high fever, and sudden death. A special vaccine (“TruFel HC2PCh” by Elanco) is available. Consider it for high-risk or shelter-exposed cats. 🚨

🧼 Prevention at Home

• 🧴 Clean shared bowls and litterboxes
• 🧍‍♂️ Wash hands after handling cats
• 🛑 Quarantine new cats
• 🧪 Test new cats for FeLV/FIV and monitor for sneezing

Herpesvirus survives 18 hours. Calicivirus can last up to 30 days—use bleach for disinfection. 🧼

📱 Ask A Vet App Support

Dealing with sneezing, congestion, or chronic URI symptoms? The Ask A Vet app helps with:

• 💬 Treatment plans for cats with sneezing or runny eyes
• 🧾 Vaccine schedules and guidance
• 📸 Review of ulcers or nasal discharge photos
• 📊 Advice on antibiotics or antiviral therapy

🏁 Final Takeaway

URIs are common—but manageable. Vaccines reduce severity. Good hygiene and stress reduction help limit flare-ups. If your cat sneezes or has discharge that doesn’t improve in 7–10 days, consult your vet or use Ask A Vet to get expert guidance. 🐱🩺❤️