Bird Flu: First Human Case Reported in US, but Public Threat Remains Low

A man in Colorado tested positive for a bird flu virus, also called avian influenza, the Colorado Department of Public Health and Environment reported Thursday, marking the first human case in the US of an H5 virus. He was working directly with infected birds at a commercial farm and is largely asymptomatic, state health officials said. 

The man is an inmate at a correctional facility and was working on the farm as part of a pre-release employment program. He’s now isolating and being treated with a common influenza drug (Tamiflu). No other human cases of an H5 virus — a group of viruses including H5N1 that have devastated millions of US birds and continue to impact the poultry industry — have been reported in the US. 

While human cases of bird flu are rare, working directly with birds increases a person’s risk of illness. The public health threat in the US is low, and this single detected case doesn’t change that, the US Centers for Disease Control and Prevention said in a statement. The CDC said it’s monitored over 2,500 people with exposure to sick birds and this has been the only case to date. 

The CDC said it’s also possible this human case was a result of “surface contamination of the nasal membrane,” rather than an actual avian influenza infection, since the affected man was working directly with sick birds and reported mild to no symptoms. 

In December 2021, the UK reported one asymptomatic human case of bird flu caused by an H5 virus in a person who had exposure to infected birds. China reported the first case of H3N8 bird flu on Tuesday, but that is a different strain than the currently circulating H5N1 strain responsible for the deaths of millions of US animals. The case in China, also, was in a young child who had direct contact with birds and officials believe risk of further spread between humans remains low.

As long as animals and humans live, work and flock around each other, there will be a risk of viruses mutating enough to make the jump from species to species. The risk of bird flu is higher for people who work directly with birds, such as poultry workers or even hunters. But the current group of H5 viruses, specifically the current H5N1 circulating among birds, aren’t thought to have the necessary mutations needed to spread easily between humans and pose a public health risk, the CDC said. 

So far, the CDC says, the current bird flu H5N1 virus lacks the mutations necessary to spread to people easily, and it may also lack the changes that have caused severe illness in people in the past. But the CDC said Thursday it will continue to monitor for genetic changes that could change the public health risk.

Here’s what to know about bird flu, or avian influenza. 

What is the bird flu?

The bird flu, aka avian influenza, is the disease caused by infection with influenza type A viruses. These viruses can circulate among birds around the world and have infected humans in rare cases, mostly those who work directly with infected birds. If the viruses mutate enough, the public health fear is that they might make the jump to spread among humans. The bird flu was first detected and controlled in 1997, but reemerged in 2003 and started spreading widely among birds.

The predominant bird flu virus in the world is H5N1, according to the CDC. Since 2003, more than 880 human cases of earlier strains of H5N1 have been reported in humans. 

Influenza viruses that cause the bird flu are either “low pathogenic” or “highly pathogenic.” Highly pathogenic bird flu can cause severe disease or death in poultry, and it’s those cases that the USDA is reporting.

The World Health Organization reports four types of influenza viruses: A, B, C and D. Type A viruses, which occur in both humans and different kinds of animals, are the biggest threat to public health and can cause pandemics, the WHO says. The “swine flu” of 2009’s pandemic was caused by a type A virus. Seasonal flu viruses in humans are caused by type A and type B viruses. 

Is it deadly? 

While human cases remain rare, about half of previous H5N1 human infections have resulted in death, the CDC said. But, as the agency noted Thursday, the current H5N1 appears different than earlier strains. Importantly, the only two reported human cases linked to the current H5N1 strain (one in the UK, and now one in the US) have been mild or asymptomatic.

But because of the potential for a serious health threat, the WHO, CDC and US Department of Agriculture are closely monitoring outbreaks in the US and in other countries. The CDC has said it has “produced a candidate vaccine virus,” if it’s needed, in response to a potential public health threat. 

“This one H5-positive human case does not change the human health risk assessment. CDC will continue to watch this situation closely for signs that the risk to human health has changed,” the CDC said Thursday. 

“Signals that could raise the public health risk might include multiple reports of H5N1 virus infections in people from exposure to birds, or identification of spread from one infected person to a close contact.” 

Where is it in the US? How is it being monitored?

The bird flu has been detected and reported by the USDA in wild and domestic birds in more than half of US states. Most outbreaks in flocks of birds have occurred on the East Coast and in the Midwest.

Henry Niman, a biochemist in Pittsburgh, has been tracking the outbreak (as reported by The New York Times), and his map offers a visual representation of the outbreak across the country.

The first case was in a wild bird in South Carolina. Other cases were reported in some backyard flocks as well as some poultry farms, where animals are raised commercially for food. Any birds of the flocks that have cases of avian flu will not enter the food system, the USDA said.

How do you catch it? 

Birds can shed avian influenza virus in their saliva, feces and mucus, according to the CDC. Humans can get sick by breathing in the virus, or by touching their eyes, nose or mouth. Most human bird flu cases have been reported in people who work directly with birds.

To avoid getting sick, avoid contact with wild birds, don’t touch dead or sick birds you see, and avoid visiting bird markets or farms if you’re traveling to another country, according to the CDC. 

Extra precautions or monitoring may be taken if you work directly with birds, if you hunt birds or if you’re a health care worker. If you have contact with an infected bird, contact your local or state health department. Here’s a directory of local health departments in the US.

To avoid contamination from poultry of any kind, make sure to properly handle your poultry and eggs, and thoroughly cook them to 165 degrees Fahrenheit, the USDA says, to kill bacteria and viruses. 

You can also report a dead bird to your local health department or wildlife agency, which will help public health officials track not only the bird flu but also viruses such as West Nile virus. Reporting dead birds could be especially important if you see more than one of them. 

So long as humans eat birds and other animal products, as well as live and work among them, there might be a risk for viruses to jump from species to species. And the threat of bird flu causing an outbreak among people isn’t new to 2022. 

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.