H5N1 ‘bird flu’ cases report conjunctivitis, teary eyes symptoms

Conjunctivitis, aside from flu-like illness, tops the list of bird-flu symptomology as public health officials caution a likely underreporting of human cases in U.S. agricultural communities. 

To date, 13 human cases of H5N1 avian influenza A, commonly known as “bird flu,” have been reported since March across Colorado, Michigan and Texas, per the Centers for Disease Control and Prevention (CDC), with four cases associated with exposure to sick dairy cows and nine with exposure to infected poultry. What’s more, some 230 people have been tested after exposure to infected animals. That’s enough for the CDC to assess a “low public health risk” for human infections, yet bird flu’s escalating toll in poultry and livestock fuels concern that human cases may be happening—yet going underreported.  

Current CDC and U.S. Department of Agriculture data show that: 

• Over 100 million aquatic birds, commercial poultry and personal/”hobbyist” flocks have been affected by H5N1 in 48 states.
• 177 dairy herds have been affected by H5N1 across 13 states. 

Testing for bird flu among the most at-risk populations—farmworkers—remains scant for various reasons, which is why a recent preprint study garnered national attention. 

Per the study posted to medRxiv on July 31, infectious disease researchers with the University of Texas Medical Branch detected signs of prior bird flu infection in workers from a pair of Texas dairy farms that experienced outbreaks earlier this year. Of 14 farmworkers who had not previously been blood-tested for the virus, researchers found two to already have antibodies. For its part, the CDC also recently published a case report on four human infections in Colorado poultry and dairy farmworkers. 

Despite the relatively small-scale nature of the study and case reports, public health officials express unease over the potential for underreporting of human bird flu cases. The concern being that a coinfection of bird flu and seasonal flu may provide a genetic reassortment allowing for an even more pathogenic flu strain, especially given how the H5N1 strain has evolved to become more infectious to mammals in recent years. 

While evidence suggests this genetic exchange isn’t happening presently, limited surveillance means officials have a slower capability to identify and intervene should a novel influenza virus appear. 

“In theory, reassortment could lead to a new influenza virus that could pose a significant public health concern: a virus that has the transmissibility of seasonal influenza and the severity of H5N1,” Nirav Shah, CDC principal deputy director, told reporters in a media update on July 30. That possibility isn’t too far off, given that the 2009 pandemic H1N1 virus is thought to have emerged from a genetic reassortment of influenza A in pigs. 

H5N1 bird flu symptoms: Why conjunctivitis? 

Human bird flu cases do appear to be mild, adding to monitoring woes, with case reports identifying a range of likely symptoms, including: 

• Conjunctivitis 
• Teary eyes 
• Fever 
• Chills 
• Coughing 
• Sore throat 
• Runny nose 
• Headache 
• Fatigue 

Of note, conjunctivitis was the only symptom in two positive bird flu cases this year while teary eyes and discomfort, in addition to cold symptoms, were present in a third. The two ocular maladies appear to be key symptomology of human bird flu. 

Conjunctivitis is a commonly reported ocular symptom of respiratory illnesses, such as flu, respiratory syncytial virus (RSV) and potentially SARS-CoV-2, the virus causing COVID-19. Andrew Morgenstern, O.D., AOA staff consultant to the AOA Evidence-Based Optometry Committee, notes that conjunctivitis is a hallmark of many ocular diseases and systemic conditions. 

“The eyes are a very strong barometer for the overall health of the human body,” Dr. Morgenstern says. “If conjunctivitis is present, that should tip off eye doctors that something is wrong, not only with the eye but also potentially systemically. That could be a sign of a communicable community disease.” 

It’s important for patients to contact their doctor if they develop conjunctivitis, especially after exposure to farm animals at the crux of the bird flu situation. A comprehensive, dilated eye examination can detect the full extent of the cause of the conjunctivitis, but it’s equally important to note that not all conjunctivitis cases should be suspected for bird flu. 

CDC issues interim recommendations on H5N1 bird flu 

That said, the CDC has issued interim recommendations for prevention, monitoring and public health investigations. These recommendations call on clinicians to consider the possibility of bird flu infection in patients with acute respiratory illness and recent exposure (within 10 days) to the virus. Exposure is defined as: 

• Close exposure (within six feet) to birds or other animals with confirmed infection, including the handling or preparation process for consumption, or consuming uncooked food products, including unpasteurized milk.
  
• Direct contact with surfaces contaminated by bird or other animal byproducts, or unpasteurized milk.
• Visiting a live bird market with confirmed bird infections or associated cases of human bird flu infections.
• Contact with a confirmed, probable or symptomatic case of human bird-flu infection without respiratory or eye protection. 

Should clinicians suspect a bird flu infection they are to contact their state public health department and encourage the patient to isolate at home away from household members, as well as not go to work or school until they are determined not to have an infection. 

Follow the CDC’s Weekly U.S. Influenza Surveillance Report for a week-by-week assessment of seasonal flu activity nationally.