The first identified human case in the United States of the H5N1 virus, known as the avian flu and typically transmitted among poultry and wild birds, has been found in a Colorado man who works on a Western Slope poultry farm.
The Colorado Department of Public Health and Environment has been monitoring and testing people exposed to poultry and wild birds infected with avian flu, according to a news release.
Earlier this week, a test revealed the presence of the influenza virus in a single nasal specimen of a man who was working on a farm with infected poultry, the news release said.
On Wednesday, the Centers for Disease Control and Prevention confirmed the test. Repeat testing on the man, however, has been negative.
Health officials said it’s possible that the virus may have been present in the person’s nose without causing infection.
“We might never know if this individual was truly infected, meaning the virus was replicating in his body, or if the virus was just transiently present in his nose and picked up by the nasal swab test,” said Dr. Rachel Herlihy, Colorado state epidemiologist.
Both the CDC and the state consider the discovery a “confirmed case,” Herlihy said. “He is the first person in the U.S. for this virus.”
Public health officials in the United Kingdom confirmed the H5N1 virus in January 2022 in a person who was asymptomatic and had direct contact with infected birds, according to the news release.
Earlier this month, the Denver Zoo shut down its outdoor bird exhibits and brought the animals inside in an effort to prevent the transmission of the highly contagious avian flu, which has been detected in Denver and other parts of Colorado.
Also in April, inspectors with the U.S. Department of Agriculture confirmed the first case of avian flu in a backyard chicken flock in Colorado, in Pitkin County.
The Colorado man, who is under age 40, is largely asymptomatic, reporting only fatigue, the state health department said. He is in isolation and receiving the influenza antiviral drug oseltamivir (tamiflu), per CDC guidance.
“Scientists believe that the risk to people is low as H5 flu viruses spread among wild birds and poultry,” the release said. “They do not normally infect humans nor spread from person to person. There are currently no known cases of this H5 flu virus spreading among people. There are no other confirmed human cases in Colorado or the United States at this time.”
The positive result is connected to a commercial farm in Montrose County. The affected flock has been euthanized and disposed of under the guidance of the Colorado Department of Agriculture and the USDA.
“We want to reassure Coloradans that the risk to them is low,” Herlihy said.
While human infections of the H5 viruses are rare, direct exposure to infected birds increases that risk. Infected birds shed flu viruses in their saliva, mucous, and feces, according to the release. People should avoid contact with poultry that appear ill or are dead, and avoid contact with surfaces that appear to be contaminated with feces from wild or domestic birds.
“We know that in general the risk to the general public is very low,” Herlihy said. “That risk is elevated in individuals who do have close contact or prolonged contact with infected birds.”
People who handle sick or dead poultry should wear gloves and wash your hands with soap and water afterwards, the release said. If possible, wear respiratory protection such as a medical facemask and eye protection such as goggles.