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Health authorities in Colorado reported the first U.S. case of a human infected with the bird flu H5 virus this week as the country as a whole faces a huge bird flu outbreak across poultry farms.
The person infected, described as an adult male younger than 40 who was working at a farm with infected poultry, is said to be largely asymptomatic and experiencing only fatigue, the Colorado Department of Public Health & Environment (CDPHE) said on Thursday.
The man's reported infection was detected in a single nasal sample. The CDPHE noted it is possible that the virus may have been present in the man's nose without causing infection simply due to his close proximity with infected birds. Still, he is now isolating and is receiving an antiviral flu drug. The affected bird flock was killed.
What is H5 bird flu?
The H5 bird flu virus is also known as Highly Pathogenic Avian Influenza (HPAI) A H5 and a few different subtypes have been reported in the U.S., known as H5N1, H5N2, and H5N8.
H5 bird flu can be highly infectious, spreading through flocks of birds and infecting their respiratory and gastrointestinal tracts. The virus has a high mortality rate in infected poultry, though outbreaks often result in millions of birds being killed anyway by farmers to prevent it from spreading.
In birds, symptoms of HPAI infections may include sudden death; lack of energy, appetite, and coordination; purple discoloration or swelling of various body parts; diarrhea; nasal discharge; coughing; sneezing; and reduced egg production, or soft-shelled or misshapen eggs, according to the U.S. Centers for Disease Control and Prevention (CDC).
Can humans catch it and is it dangerous?
Bird flu infections in humans have ranged in severity from no symptoms or mild illness to severe disease that resulted in death.
Yes, it is possible for humans to catch H5 bird flu, though this is rare and the Colorado case is the first reported infection in the U.S., according to the CDC.
In other countries, humans infected with the virus have displayed symptoms similar to seasonal influenza, but their disease may progress to lower respiratory tract illness and even severe pneumonia, multi-organ failure, and septic shock, the CDC states.
Most human infections with H5 bird flu viruses have occurred in people not using appropriate personal protective equipment who were either in direct physical contact with infected birds or contaminated surfaces; were in close proximity to infected birds; or visiting a live poultry market.
Otherwise, the CDC states that the public health risk of bird-to-human transmission of H5 bird flu viruses "is thought to be low" and preliminary lab studies suggest the viruses "are not well-adapted to humans". Risk of infection may increase with exposure to infected birds.
Human-to-human transmission of bird flu in general is described by the CDC as "very rare", though it has happened. Due to the possibility that the viruses could evolve to better spread between people, the agency states that monitoring for person-to-person spread is "extremely important for public health."
The current U.S. bird flu epidemic
The U.S. is currently experiencing a large outbreak of HPAI bird flu that has been confirmed in 29 states and affected more than 33 million birds, according to the U.S. Department of Agriculture on April 27.
"Highly pathogenic avian influenza is a serious concern for our nation's poultry industry, and we need to continue our nationwide response to minimize the impact," said USDA Under Secretary for Marketing and Regulatory Programs Jenny Lester Moffitt in an agency press release.
