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Entry 551Filed under Breeding

CDC Removed Cat Bird Flu Data. It Raised Questions—But Did Not Prove Cat-to-Human H5N1 Spread

A reported 2025 CDC-linked table raised questions about cat-related H5N1 spread but did not prove a transmission chain. A separate 2026 CDC investigation found serologic evidence of possible transmission to one exposed veterinary professional.
7-minute read By Animalso Team
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Did the CDC remove data showing that cats spread bird flu to people? A table was briefly reported as posted and then removed, but it did not prove cat-to-human H5N1 spread. A later CDC investigation found serologic evidence consistent with possible transmission to one exposed veterinary professional, but it did not directly observe or confirm a transmission chain.

The February 2025 CDC report confirmed H5N1 infection in two indoor cats in Michigan dairy-worker households; the workers were not tested for H5, so the cause of their reported symptoms was unknown. In May 2026, CDC reported H5N1-specific antibodies in one of 25 exposed people tested after contact with infected cats and characterized the finding as evidence of possible transmission.

What was reportedly removed

In early February 2025, The New York Times reported that information about possible bird-flu transmission involving cats and people had briefly appeared on a CDC website or in a CDC-associated report before disappearing. The reported table appeared to describe possible transmission events in two households. One scenario reportedly suggested that an infected cat may have infected another cat and a human adolescent.

Those details came from contemporaneous reporting about a table that was removed. They are not the same as a final CDC finding. The table’s disappearance does not prove that its strongest implication was correct, and the available record does not establish why it was posted or removed.

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The accurate takeaway is that the reported data raised questions about household transmission involving cats, but did not establish a confirmed transmission chain. Later evidence adds a separate, qualified signal of possible cat-to-human transmission.

What the official Michigan investigation established

The formal CDC publication most closely connected to the controversy was an MMWR report published on February 20, 2025. It described two indoor domestic cats in separate Michigan dairy-worker households that became infected with highly pathogenic avian influenza A(H5N1).

Both cats developed respiratory and neurologic illness. They lived in households associated with dairy workers, and neither cat was known to have direct outdoor exposure. Laboratory sequencing identified clade 2.3.4.4b, genotype B3.13. The viruses were reported as indistinguishable from viruses circulating in Michigan dairy cattle.

Investigators could not determine the precise route of infection for either cat. Neither dairy worker received H5 testing, so CDC said it was unknown whether the workers’ reported gastrointestinal or ocular symptoms were caused by H5N1 or another condition. The report did not establish that a worker infected a cat, a cat infected a person, or one cat infected another.

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What the 2026 investigation found—and did not prove

A separate CDC investigation published May 7, 2026, examined people exposed to cats infected with H5N1 in Los Angeles County. Of 139 exposed people invited, 25 had blood serum tested. One asymptomatic veterinary professional had antibodies specific to the H5N1 clade identified in the infected cats.

CDC authors described the result as “serologic evidence of possible transmission” from a domestic cat to a human. The person reported no influenza-like illness after exposure and had no other known risk factors. The person did not use respiratory or eye protection during exposure.

Antibodies are evidence of an immune response, not a directly observed transmission event. This finding supports possible cat-to-human transmission, but it does not establish a virologically confirmed chain showing exactly when or how infection occurred. It also does not change the fact that the 2025 Michigan investigation left transmission direction unresolved.

How the evidence compares

Evidence What it found What it establishes
Reported 2025 table Contemporary reporting described possible household transmission involving cats and a person. It raised questions; it was not a final CDC finding or proof of a transmission chain.
February 2025 Michigan CDC report Two indoor cats tested positive for H5N1; household dairy workers were not tested for H5. Confirmed infection in the cats, but not the route or direction of transmission.
May 2026 Los Angeles County CDC investigation One of 25 tested exposed people had antibodies specific to the clade found in infected cats. CDC called this serologic evidence of possible cat-to-human transmission, not a directly observed or confirmed chain.

A separate 2026 study found H5N1 antibodies in cats near dairy farms

A CDC Emerging Infectious Diseases study published in September 2026 reported seropositivity in 25% of 73 domestic cats sampled within 2 km (1.2 miles) of dairy farms in California. The authors said proximity may be a risk factor, but they could not determine the source of infection for each seropositive cat. They also said the route, including human-to-cat transmission, could not be confirmed.

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This study supports concern about animal exposure and the value of surveillance. It is not evidence that cats transmitted H5N1 to people, and its cat serology results should not be treated as comparable to human infection counts.

How an indoor cat could be exposed to H5N1

Indoor-only status lowers some risks, particularly contact with wild birds and other outdoor animals, but it does not create a sealed environment. Possible exposure routes include infected birds or other animals, contaminated materials brought into the home, and contaminated food.

CDC and the FDA advise against feeding cats raw pet food or unpasteurized milk. Choose cooked or appropriately processed, complete-and-balanced pet food for ordinary feeding. Do not treat raw milk or raw meat as harmless because it is intended for an animal.

Symptoms to watch for in cats

Reported warning signs of H5N1 in cats can include:

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  • fever;
  • unusual tiredness or lethargy;
  • reduced appetite;
  • red or inflamed eyes;
  • discharge from the eyes or nose;
  • difficulty breathing; and
  • neurologic signs such as tremors, seizures, incoordination, or blindness.

These symptoms are not specific enough to diagnose H5N1 at home. A cat with respiratory, eye, appetite, or neurologic symptoms may have another serious illness. Diagnosis requires veterinary assessment and, where appropriate, testing coordinated with animal-health or public-health authorities.

What owners should do after a possible exposure

  1. Call a veterinarian promptly. Explain the symptoms and mention possible contact with sick or dead birds, poultry, dairy cattle, an infected animal, raw pet food, uncooked meat, or unpasteurized milk.
  2. Ask before bringing the cat to the clinic. The veterinary team can give instructions to reduce exposure to staff, other animals, and people in the waiting room.
  3. Do not try to diagnose the cat at home. Do not assume an indoor cat has H5N1—or that a sick cat cannot have it—based only on symptoms.
  4. Follow public-health or animal-health instructions. A veterinarian may coordinate with relevant authorities if the exposure history makes avian influenza plausible.
  5. Monitor people in the household. Anyone with close exposure should tell a healthcare professional about the animal exposure if they develop compatible symptoms.

A veterinarian or public-health official can provide situation-specific advice about handling a cat suspected of having an infectious disease, including precautions around respiratory secretions, eye discharge, saliva, and contaminated bedding.

When bird-flu PPE makes sense

Routine respirator use is not a requirement for every person who owns a cat. CDC workplace guidance is aimed at people with direct or close exposure to suspected or confirmed infected animals or contaminated materials, including veterinarians, animal handlers, dairy workers, responders, and laboratory or field personnel.

For higher-exposure situations, CDC recommends a NIOSH-approved particulate respirator, such as a NIOSH-approved N95 respirator, along with appropriate eye protection, gloves, protective clothing, and foot protection. Precautions depend on the task and the risk of contact with secretions or contaminated material. An N95 alone is not complete protection; follow official workplace guidance.

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Why the removed information still matters

The posting-and-removal episode remains a transparency question even though the reported table did not prove cat-to-human spread. Public-health agencies have to communicate while investigations are incomplete, and the way preliminary information is labeled affects how people interpret risk to themselves, their families, and their pets.

A clear account should distinguish what was reportedly posted, what it appeared to suggest, and what later investigations established. The 2025 Michigan report confirmed H5N1 infection in two indoor cats but left the route unresolved. The 2026 CDC investigation added serologic evidence of possible transmission to one exposed veterinary professional, without directly confirming a transmission chain. The reason for the earlier table’s removal remains unverified.

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The bottom line for cat owners

The reported 2025 table raised questions but did not prove that cats spread H5N1 to people. The official Michigan investigation confirmed infection in two indoor cats and could not establish how they became infected or whether they infected anyone.

Separate CDC evidence published in 2026 found antibodies consistent with possible H5N1 transmission to one exposed veterinary professional. That is a meaningful signal, not a directly observed or virologically confirmed transmission chain. Avoid feeding cats raw pet food or unpasteurized milk, contact a veterinarian about compatible symptoms or plausible exposure, and follow task-appropriate PPE guidance when handling a suspected infected animal.

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FAQ

Did the CDC confirm that cats spread H5N1 to people?

The 2025 Michigan investigation did not confirm cat-to-human transmission. A separate 2026 CDC investigation found serologic evidence of possible transmission in one exposed veterinary professional, but did not directly observe or confirm a transmission chain.

What did the 2026 CDC investigation find?

Of 139 people invited after exposure to infected cats in Los Angeles County, 25 had serum tested. One asymptomatic veterinary professional had antibodies specific to the H5N1 clade identified in the cats. CDC described this as serologic evidence of possible transmission.

Can an indoor cat get bird flu?

Yes. Indoor cats can be exposed indirectly through contaminated materials, infected animals, or contaminated food. Indoor-only status reduces some risks but does not eliminate them.

Should cats be fed raw food or unpasteurized milk?

No. CDC and the FDA advise against feeding cats raw pet food or unpasteurized milk. Cooked or appropriately processed complete-and-balanced food is the safer ordinary feeding option.

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What should I do if my cat develops possible bird-flu symptoms?

Contact a veterinarian promptly, describe the symptoms and possible exposure, and ask how to bring the cat in safely. Symptoms can include lethargy, appetite loss, eye or nose discharge, breathing difficulty, fever, and neurologic signs. Do not try to diagnose H5N1 at home.

Has an avian influenza virus ever spread from a cat to a human?

Yes. During a 2016 outbreak of influenza A(H7N2) among New York City shelter cats, a veterinarian became infected after prolonged exposure to sick cats without recommended PPE. H7N2 is different from H5N1; that event does not establish what happened in the Michigan H5N1 cases.

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