In a laboratory-confirmed series of 22 cats from Poland's 2023 outbreak, all 22 died or were euthanized, and most went from the first vague sign to death within three days. Their fevers ran 39.6–41°C (103.3–105.8°F). A fever combined with a wobbly walk is not a wait-and-see situation in a cat.
Three numbers that define feline H5N1
Guidance for cats keeps returning to the same three figures, each changing what you do next.
- 1 to 5 days from exposure to the first sign. Experimental infections show signs at about 2 days, and nasal shedding begins around day 3.
- 24 to 72 hours from the first sign to severe breathing difficulty or death in the Polish cohort.
- More than 70% mortality in clinically affected cats, per CSTE guidance; the Polish series was 100% (22 of 22).
How a house cat gets exposed
The virus does not require a farm visit. Six of the 22 Polish cats were strictly indoor animals whose only identified risk was raw poultry meat in the bowl. In the US outbreak that began in 2024, more than 40 domestic cats were reported to USDA, most of them linked to affected dairy farms.
- Raw or undercooked poultry, including commercial raw pet food made from it.
- Unpasteurized milk, cream or colostrum.
- Hunting or scavenging infected wild birds and rodents.
- Contaminated boots, clothing, bedding or equipment carried in by someone who works with poultry, dairy cattle or wildlife.
Cooking is the reliable fix: 74°C (165°F) at the centre inactivates the virus, and pasteurization does the same for milk. Cooking temperatures and recall history are in our H5N1 raw food guide.
The first 12 hours: signs owners explain away
Early H5N1 looks like a hundred ordinary illnesses. The cat stops eating, sleeps in a cupboard, feels hot behind the ears. In the Polish records, owners most often reported loss of appetite, lethargy and apathy before anything dramatic happened.
What sets it apart is speed, and the company those signs keep. A temperature of 39.6°C or higher alongside heavy discharge from both eyes and nose, within a day or two of each other, deserves a phone call. Fever alone is common; fever plus stiff hind legs is not. Technique and the normal range are in taking a cat's temperature.
Neurologic signs that separate H5N1 from a cold
Feline upper respiratory infections sneeze and discharge. H5N1 reaches the brain. The Polish cats showed a consistent set of neurologic findings, often on the same day as the breathing trouble.
| Sign | What you actually see | Action |
|---|---|---|
| Anisocoria | One pupil wide, one narrow, changing through the day | Emergency |
| Ataxia | Drunken walk, crossed legs, falling against walls | Emergency |
| Paraplegia | Dragging the hind legs, unable to stand | Emergency |
| Seizures | Paddling, jaw champing, loss of consciousness | Emergency |
| Sudden blindness | Walks into furniture, pupils fixed wide | Emergency |
| Salivation, head tilt | Drooling, head turned to one side | Same-day call |
Rabies produces an almost identical picture and has to be ruled out first in any cat with neurologic signs, which is one reason the reporting step below is not optional.
Why 24 to 72 hours decides the outcome
By the time a cat is gasping, the lungs are already consolidating. Imaging in the Polish cohort showed interstitial to diffuse pneumonia, and lung ultrasound found numerous B-lines. Blood work showed thrombocytopenia in 64% of tested cats, eosinopenia in 86% and lymphopenia in 36%, with raised AST, LDH and CK: a picture of systemic injury rather than a simple airway infection.
That is why antibiotics do nothing and waiting costs the cat the window. Care is supportive: oxygen, fluids, nursing, sometimes anticonvulsants. No vaccine is licensed for cats and no antiviral is approved for feline H5N1; human influenza drugs are not a home remedy, and dosing a cat with them is dangerous.
The first hour at home
- Move the cat into one room and close the door. No shared litter trays or bowls with other cats.
- Call the clinic before you drive. Say the cat has fever, neurologic signs or laboured breathing, and mention raw food, raw milk, poultry work or a dead bird in the garden.
- Keep handling to one adult, with gloves and a mask, and change clothes afterwards.
- Clean bowls, trays and bedding with an EPA-registered disinfectant effective against avian influenza, then wash your hands for 20 seconds.
- Do not give human flu medicine, leftover antibiotics or supplements. None of them treat the virus, and all of them add risk.
Testing and reporting: what your vet needs
An oropharyngeal swab is the preferred antemortem sample; both nares, urine, serum and whole blood are also accepted. Rapid in-clinic influenza tests are not validated in cats, so samples go to a reference or NAHLN laboratory. If the cat has died, brain and lung are the tissues of interest, and rabies testing runs first.
A suspected case is reported to the state animal health official, the state public health veterinarian or the state diagnostic laboratory, not simply noted in the record. Ask the laboratory to test any raw food left in the bowl as well, because that is how several recalls began.
Protecting people in the same house
Cat-to-human transmission is rare but real: a New York veterinarian was infected by a sick cat in 2016, and a veterinary professional exposed to an infected cat tested positive without symptoms during the 2025 US outbreak. CDC advises monitoring anyone exposed for fever, respiratory signs and conjunctivitis for 10 days after the last contact. Keep the cat confined until 5 days after clinical signs resolve, and keep immunocompromised household members away from it entirely.
Prevention if your cat eats raw food or goes outside
Cook all poultry to 74°C, skip raw milk and raw commercial diets while outbreaks are active, and keep cats indoors or in a secure enclosure where the virus is circulating. If you work with poultry, dairy cattle or wildlife, change clothes and shoes before greeting your cat. Our indoor enrichment guide covers keeping a confined cat occupied.
When to go tonight
One seizure, open-mouth breathing, sudden blindness, hind-leg paralysis, or a temperature above 40°C with lethargy means emergency care now rather than in the morning. Car-journey steps are in the collapsed cat protocol, seizure timing in seizures in cats, and breathing patterns in open-mouth breathing.
What this article cannot do
This guide is educational and does not replace a veterinary examination. H5N1 is a notifiable zoonosis in many jurisdictions: if you suspect it, contact your veterinarian and your local animal or public health authority the same day.
Frequently asked
How long after exposure would a cat show signs of H5N1?
Most guidance puts the incubation period at 1 to 5 days. Experimental infections produced signs at roughly 2 days, with nasal shedding starting around day 3 and continuing for four days or more. That short window is why a known exposure — raw poultry, raw milk, a dead bird — matters more than the symptom itself.
Can my other cats catch it from the sick one?
Cat-to-cat spread through respiratory secretions has been shown experimentally, but how often it happens in households is still unclear, which is why suspected cases are isolated. Keep the sick cat in a separate room with its own litter tray and bowls until 5 days after clinical signs resolve, and ask your veterinarian or public health contact how long to watch the other cats.
Is there a treatment or a vaccine if my cat tests positive?
No vaccine is licensed for cats against H5N1, and there is no approved antiviral for feline infection. Care is supportive — oxygen, intravenous fluids, nursing, seizure control if needed. Human influenza antivirals are not a substitute and must not be given at home; any use in a cat is a veterinary decision made under supervision.