Feline Calicivirus (FCV): Accounting for most remaining cases, calicivirus often causes oral ulcers in addition to respiratory symptoms. Some strains can lead to severe systemic disease.

Bacterial Agents: Secondary bacterial infections frequently complicate viral URIs. Common culprits include:

• Chlamydophila felis
• Bordetella bronchiseptica
• Mycoplasma species

How URIs Spread

Feline upper respiratory infections are highly contagious and spread through:

Direct Contact: Nose-to-nose contact between cats allows efficient transmission of viruses and bacteria.

Aerosol Transmission: Sneezing and coughing propel infectious particles into the air that other cats can inhale.

Fomite Transmission: Shared food bowls, litter boxes, bedding, and even human hands can carry the virus between cats. FHV-1 can survive up to 18 hours on surfaces, while calicivirus persists for up to 30 days.

Carrier State: Cats infected with herpesvirus become lifelong carriers, shedding the virus intermittently, especially during stress. This explains why seemingly healthy cats can suddenly develop symptoms or infect others.

Recognizing URI Symptoms

Symptom severity varies widely based on the causative agent, the cat's age, immune status, and whether secondary infections develop.

Common Symptoms

Nasal Signs:

• Sneezing, often frequent and violent
• Runny nose with clear, yellow, or green discharge
• Nasal congestion causing open-mouth breathing
• Reduced sense of smell

Ocular Symptoms:

• Watery eyes
• Conjunctivitis (red, inflamed eye membranes)
• Eye discharge ranging from clear to thick and colored
• Squinting or pawing at eyes
• Corneal ulcers (particularly with herpesvirus)

Oral Manifestations:

• Ulcers on the tongue, gums, or hard palate (a classic calicivirus sign)
• Excessive drooling
• Difficulty eating due to mouth pain
• Bad breath

Systemic Signs:

• Lethargy and reduced activity
• Loss of appetite
• Fever (often 103–105°F)
• Dehydration
• Enlarged lymph nodes

Severity Variations

Mild Cases: Sneezing, clear nasal discharge, mild lethargy, maintained appetite.

Moderate Cases: Thick discharge, conjunctivitis, reduced eating, noticeable fever.

Severe Cases: Significant dehydration, refusal to eat for 24+ hours, difficulty breathing, ulcers, high fever.

Symptoms Requiring Emergency Care

Seek immediate veterinary attention if your cat shows:

• Open-mouth breathing, gasping, or labored breathing
• Complete refusal to eat or drink for 24+ hours
• Signs of severe dehydration (sunken eyes, skin tenting, extreme lethargy)
• Collapse or extreme weakness
• High fever (above 105°F)
• Neurological signs (seizures, disorientation)

High-Risk Populations

Certain cats face elevated risks for severe URI complications:

Kittens: Immature immune systems make kittens particularly vulnerable. URI is a leading cause of death in shelter kittens.

Senior Cats: Age-related immune decline increases susceptibility and complication risks.

Immunocompromised Cats: Conditions like FIV, FeLV, diabetes, cancer treatment, or other immune-suppressing illnesses dramatically increase severity.

Flat-Faced (Brachycephalic) Breeds: Persian, Himalayan, and Exotic Shorthair cats often experience more severe symptoms due to their shortened nasal passages.

Unvaccinated Cats: Lack of core vaccinations leaves cats vulnerable to preventable strains.

Shelter and Cattery Cats: High-density housing facilitates rapid disease spread.

Diagnosis Process

Veterinary Examination

Your veterinarian will perform a comprehensive physical examination focusing on:

• Temperature measurement
• Assessment of hydration status
• Thorough oral examination for ulcers
• Eye examination for ulcers or severe inflammation
• Listening to heart and lungs
• Evaluation of lymph nodes

Diagnostic Testing

While many URIs are diagnosed clinically, testing may include:

PCR Testing: Polymerase chain reaction tests can identify specific viral or bacterial agents from swabs of the eye, nose, or throat. This is particularly useful in:

• Multi-cat households with ongoing outbreaks
• Recurrent or persistent cases
• Breeding catteries

Bacterial Culture: If a bacterial infection is suspected or antibiotic treatment fails, cultures identify the specific bacteria and appropriate antibiotics.

Blood Work: A complete blood count and chemistry panel evaluate overall health and identify complicating factors.

FIV/FeLV Testing: Especially important for outdoor cats or those with an unknown history, as these viruses compromise immune function.

Imaging: In severe or persistent cases, X-rays may rule out pneumonia or other complications.

Treatment Approaches

Treatment varies based on severity, causative agent, and individual patient factors.

Supportive Care (Mild to Moderate Cases)

Most URIs, particularly those caused by herpesvirus, are viral and don't respond to antibiotics. Treatment focuses on supportive care:

Hydration: Maintaining adequate fluid intake is crucial. Strategies include:

• Offering fresh water in multiple locations
• Using pet fountains to encourage drinking
• Adding water or broth to food
• Subcutaneous fluids administered by a veterinarian if needed

Nutrition: Cats won't eat what they can't smell. Tactics to maintain food intake:

• Warming food to enhance aroma
• Offering strongly scented foods (fish-based, warmed)
• Hand-feeding or syringe feeding if necessary
• Appetite stimulants (e.g., mirtazapine) prescribed by a veterinarian

Nursing Care at Home:

• Gently cleaning eye and nose discharge with a warm, damp cloth
• Running a humidifier to ease congestion
• Isolating the sick cat from other cats to prevent spread
• Providing a quiet, stress-free recovery environment

Medical Interventions

Antibiotics: While ineffective against viruses, antibiotics treat secondary bacterial infections. Common options include doxycycline, clavamox, and azithromycin.

Antiviral Medications: For severe herpesvirus cases, medications like famciclovir may be prescribed.

Eye Medications: For conjunctivitis or ulcers, antibiotic or antiviral eye drops/ointments and lubricating drops may be necessary.

Pain Management: Veterinarian-prescribed NSAIDs formulated for cats can reduce fever and discomfort, improving appetite and activity.

Nebulization: In cases of severe congestion, veterinary nebulization therapy helps clear airways.

Hospitalization

Severe cases requiring hospitalization may receive:

• Intravenous fluid therapy
• Nutritional support via feeding tube if needed
• Oxygen therapy for respiratory distress
• Intensive monitoring and nursing care

Cost Breakdown

Understanding potential expenses helps with financial planning:

Typical mild case: $100 – $300
Moderate case with complications: $400 – $800
Severe case requiring hospitalization: $1,500 – $4,000+

Pet insurance typically covers URI treatment, with most policies reimbursing 70–90% of costs after the deductible.

Home Care and Recovery

Creating a Recovery Environment

Isolation: Keep infected cats separate from healthy cats, using separate food bowls, litter boxes, and bedding. Continue isolation for at least 2 weeks after symptoms resolve, or as directed by your veterinarian.

Stress Reduction: Stress triggers herpesvirus recurrences. Maintain a quiet environment, consistent routines, and minimize changes during recovery.

Humidity: Run a cool-mist humidifier to ease congestion and soothe irritated airways. Ensure good ventilation to prevent mold growth.

Nutrition Support: Offer highly palatable, aromatic foods. Warm food slightly to enhance smell. Hand-feeding or offering food on your finger may entice eating.

Monitoring Recovery

Track these indicators of improvement:

• Eating and drinking voluntarily
• Reduced discharge from eyes and nose
• Less frequent sneezing
• Return of normal energy levels
• Resolution of fever

Most cats show improvement within 3–5 days, with complete recovery in 2–3 weeks. However, herpesvirus carriers may experience periodic recurrences throughout life.

Prevention Strategies

Vaccination

Core vaccines (FVRCP) protect against herpesvirus, calicivirus, and panleukopenia. While not 100% effective at preventing infection, vaccinated cats typically experience milder symptoms.

Kitten Series: Starting at 6–8 weeks, with boosters every 3–4 weeks until 16–20 weeks.
Adult Boosters: Every 1–3 years depending on risk and vaccine type.
Cost: $25 – $50 per vaccination.

Environmental Management

Quarantine: Isolate new cats for 2–3 weeks before introducing them to resident cats. Have new cats examined and tested by a veterinarian first.

Sanitation: Regular disinfection reduces environmental contamination:

• Use a dilute bleach solution (1:32) for hard surfaces
• Wash bedding in hot water
• Replace or thoroughly disinfect shared items after an infection

Stress Management: Minimize stress through:

• Adequate resources (multiple food stations, litter boxes, resting areas)
• Environmental enrichment (toys, scratching posts, perches)
• Pheromone diffusers (e.g., Feliway)
• Consistent daily routines

Population Control: Avoid overcrowding, which increases stress and disease transmission. Follow the "one-plus-one" rule for litter boxes: one box per cat, plus one extra.

Breeding Considerations

Testing: Test breeding cats for herpesvirus and calicivirus.
Isolation: Isolate pregnant queens and kittens from other cats.
Early Weaning: In some cases, early weaning and hand-rearing protect kittens from maternal transmission.

Long-Term Management of Carrier Cats

Cats infected with herpesvirus become lifelong carriers. Management focuses on minimizing recurrences:

Lysine Supplementation

L-lysine may reduce herpesvirus replication and recurrence frequency:

• Typical dose: 250–500mg twice daily
• Available as treats, powders, or gels
• Evidence for effectiveness is mixed; always discuss with your veterinarian

Stress Reduction

Identify and minimize stress triggers:

• Major household changes
• New pets or family members
• Travel or boarding
• Construction or loud noises
• Inadequate resources in multi-cat homes

Regular Veterinary Care

Maintain wellness examinations to catch early signs of recurrence and manage any underlying conditions that could compromise immune function.

Complications and Prognosis

Potential Complications

Pneumonia: Lower respiratory tract involvement can develop, particularly in kittens and immunocompromised cats.

Chronic Rhinitis: Some cats develop persistent nasal inflammation causing ongoing congestion and discharge.

Corneal Sequestrum: Herpesvirus can cause severe eye damage requiring surgery.

Secondary Infections: Bacterial complications can extend illness duration and severity.

Weight Loss: Prolonged appetite suppression leads to dangerous weight loss, especially in kittens.

Prognosis

Healthy Adult Cats: Excellent prognosis with supportive care; most recover fully within 2–3 weeks.

Kittens: Guarded prognosis; prompt veterinary care significantly improves outcomes.

Immunocompromised Cats: Variable prognosis depending on the underlying condition and quality of care.

Chronic Carriers: Good long-term prognosis with proper management, though recurrences may occur throughout life.

When to Seek Veterinary Care

Schedule a Regular Appointment If:

• Symptoms persist beyond 7–10 days
• Discharge becomes thick and colored
• Your cat's appetite decreases significantly
• You have multiple affected cats

Seek Emergency Care If:

• Your cat struggles to breathe or is gasping
• Complete appetite loss for 24+ hours
• Extreme lethargy or collapse
• Signs of severe dehydration (sunken eyes, skin tenting)
• Neurological symptoms (seizures, disorientation)

Myths and Misconceptions

Myth: URIs are not serious and always resolve on their own.
Reality: While mild cases often self-resolve, URIs can become life-threatening, especially in vulnerable cats.

Myth: Antibiotics cure feline URIs.
Reality: Most URIs are viral; antibiotics only treat secondary bacterial infections.

Myth: Vaccinated cats can't get URIs.
Reality: Vaccines reduce severity but don't prevent all infections.

Myth: Lysine cures herpesvirus.
Reality: Lysine may reduce recurrence frequency but doesn't eliminate the virus.

Myth: Once recovered, cats are immune.
Reality: Herpesvirus carriers remain susceptible to recurrences throughout life.

Conclusion

Feline upper respiratory infections, while common, require attentive care and appropriate treatment to ensure a full recovery. Understanding the symptoms, implementing preventive measures, and knowing when to seek veterinary care empowers cat owners to protect their pets' health. While the herpesvirus carrier state presents ongoing management challenges, most cats with proper care enjoy long, healthy lives with minimal recurrence issues.

Remember that early intervention significantly improves outcomes, particularly for vulnerable populations like kittens and senior cats. When in doubt, consult your veterinarian—prompt treatment can prevent mild cases from becoming serious, expensive emergencies.