Health officials warn of new Bird Flu symptom in humans

Health officials are urging medical providers across the United States to watch for conjunctivitis – or eye inflammation – as a potential early warning sign of H5N1 bird flu in patients who have had contact with infected livestock, marking a significant shift in how the virus presents in humans.

The Centers for Disease Control and Prevention has reported 70 human cases of H5N1 across 12 states since 2024, with most infections linked to exposure to sick dairy cows and poultry. Though the CDC maintains that public health risks remain low, the agency has intensified surveillance efforts nationwide.

According to the American Academy of Ophthalmology, many patients initially developed conjunctivitis sometimes as their only symptom. This differs from historical H5N1 cases, which typically began with respiratory symptoms.

"Multiple human H5N1 infections, presumably transmitted from sick cows and poultry, presented with conjunctivitis as the sole clinical sign and symptom," the CDC stated in its guidance for healthcare providers. The agency recommends considering H5N1 infection in patients with eye inflammation who report contact with livestock within 10 days before symptoms appear.

Of 41 cases linked to dairy operations and 24 cases connected to poultry farms, specific instances showed higher viral presence in eye swabs than upper respiratory specimens, according to CDC data updated Feb. 21.

A cluster of cases at two Colorado poultry facilities in August 2024 illustrated this pattern. Five of nine workers who tested positive had the virus detected only in eye swabs. All nine developed Conjunctivitis, with seven reporting excessive tearing. While six experienced fever or chills, respiratory symptoms were less common.

The virus has spread widely through bird populations, with more than 12,000 infected wild birds detected across 51 jurisdictions since monitoring began in January 2022. The outbreak has affected over 162 million poultry birds and 973 dairy herds across 16 states.

Since February 2024, the CDC has tested more than 136,000 specimens through its influenza surveillance system to monitor human cases. The agency has also tracked over 15,200 people exposed to infected animals, testing more than 830 who developed symptoms.

Prevention measures focus on protecting workers and others who may contact infected animals. The CDC recommends wearing appropriate protective equipment, including N95 masks and eye protection when working with potentially infected animals. Additional precautions include removing bird feeders and shared bird baths, avoiding unprotected contact with sick or dead animals, and not consuming unpasteurized dairy products.

The CDC notes while seasonal flu vaccines cannot prevent H5N1 infection, they may simultaneously reduce the risk of getting sick with both human and bird flu viruses. Heat treatment of milk appears to inactivate the avian influenza virus.

Healthcare facilities must implement strict infection control protocols when evaluating suspected cases, including airborne precautions and use of personal protective equipment.

One death has been reported in Louisiana, while most cases have experienced mild illness. Three veterinary practitioners showed evidence of recent H5N1 infection during a CDC serosurvey of 150 veterinarians, though all three were asymptomatic.

The CDC updates case counts by 5 p.m. EST on Mondays, Wednesdays, and Fridays. While person-to-person transmission has not been documented in the current outbreak, health officials emphasize the importance of early detection and appropriate precautions given the virus's potential to mutate.

Local health departments request immediate reporting of suspected cases, particularly in patients with eye symptoms and relevant exposure history. Testing is coordinated through public health laboratories, and treatment recommendations include prompt administration of antiviral medications.