For the Birds

By Peter Galvin, MD

As you may know, the sky-high price of eggs that was seen earlier this year was directly related to bird flu, which is a highly contagious form of influenza. Yes, the same influenza virus that infects humans, but there are some differences. Influenza has four subtypes – A, B, C, and D. Most human flu cases are caused by type A, with type B responsible for a small percentage of human cases. Types C and D almost exclusively infect animals. Influenza A has multiple variants, which are classified based on the proteins found on the outer coat of the virus particle. There are 16 H, for haemagglutinin, and 11 N, for neuraminidase, proteins. Thus, type A influenza is typed using H and N proteins, for example H1N1.

Bird flu infection is widespread among birds and poultry, has been seen in dairy cows, and is spread by viral particles from fluids and secretions of infected animals (saliva, mucus, feces, and milk). Bird flu spreads easily among birds and human infections, although rare, can occur when these bird secretions are inhaled or get into a person’s eyes, nose, or mouth. Bird flu spread from human to human is extremely rare and usually occurs after prolonged contact with sick individuals in the same family. Most bird flu infections are caused by the H5N1 and H7N9 variants.

Symptoms of bird flu in humans, which typically develop two to seven days after exposure to the virus, are similar to seasonal influenza and may include fever, cough, sore throat, runny nose, eye redness (conjunctivitis), muscle aches, headaches, and fatigue. Complications of severe avian influenza, while rare, include pneumonia, respiratory failure, and inflammation of the brain (meningoencephalitis). An outbreak of H5N1 in the US began in April 2024. As of January 6, 2025, there have been 66 reported confirmed cases of bird flu in humans, with most cases among people exposed to sick animals (e.g., poultry and dairy workers). In the current U.S. outbreak, most cases have been mild, but the first human death was reported on January 6, 2025. Eye redness has been the most common symptom, although respiratory symptoms and fever have been reported. No human-to-human transmission has been reported in the current outbreak.

Anyone with flu symptoms who has been exposed to animals or a human with a confirmed or probable bird flu infection should be tested using a nasal-oral swab. For those with isolated eye symptoms, an eyelid swab cab be performed. Bird flu can be prevented by avoiding direct contact with sick or dead wild or domestic birds or dairy cows, and by not consuming raw milk. Sick or dead birds should be reported to local agencies for further investigation. Seasonal flu vaccines do not protect against bird flu. Prophylaxis with the antiviral medication oseltamivir (Tamiflu) may be considered for those with a confirmed exposure to bird flu, depending on the type and duration of exposure, time since exposure, and whether the exposed person has a high risk of complications. Oseltamivir is also recommended for treatment of those with confirmed bird flu. As with seasonal flu, early treatment (within 24 to 48 hours after illness onset) helps to prevent severe illness.

For more information go to: www.cdc.gov/bird-flu/site.html

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