Yes, sparrows can get bird flu, and they are highly susceptible to it. House sparrows and Eurasian tree sparrows infected with the H5N1 strain of highly pathogenic avian influenza (HPAI) die at rates between 66% and 100%, often within just four to seven days. Their small size and close contact with both wild waterfowl and backyard poultry make them a notable link in how the virus moves through the environment.
How Easily Sparrows Get Infected
Sparrows require only a very small amount of virus to become infected. Laboratory studies have found that the infectious dose for house sparrows is remarkably low, around 500 viral particles for some H5N1 strains. For context, that is far less than what many other bird species need to develop an active infection. Once exposed, sparrows begin shedding the virus from both their mouth and their digestive tract within a day, sometimes several days before they show any visible signs of illness.
Not every strain hits sparrows equally hard. In one CDC-supported study, certain H5N1 isolates killed 100% of inoculated sparrows, while a different isolate from the same virus family replicated poorly and caused no deaths at all. The outcome depends heavily on which genetic variant of the virus a sparrow encounters.
Symptoms and How Quickly They Progress
Infected sparrows can show a range of signs: respiratory distress, gastrointestinal problems, eye swelling, and neurological symptoms like tremors and seizures. They also become depressed and lethargic, often huddling on the ground with ruffled feathers. In practice, though, many sparrows die so quickly that observers never notice symptoms at all. One study in the Journal of Virology found that sparrows died an average of 4.1 days after infection, and death often came overnight without any prior visible illness.
This rapid timeline makes it difficult to identify sick sparrows in the wild. A sparrow that looks healthy one afternoon may be dead the next morning, which is part of why surveillance in songbird populations is so challenging.
Can Sparrows Spread Bird Flu?
Sparrows shed high levels of virus from their throat and, to a lesser extent, their cloaca (the opening birds use for both digestion and reproduction). Virus has also been detected at high concentrations in the organs of dead sparrows and in contaminated drinking water and fecal samples in their environment. In a study of Eurasian tree sparrows exposed to infected ducks, 67% picked up the virus, and half of those birds died.
Here’s the surprising part: despite shedding plenty of virus, sparrows appear to be poor at spreading it to other sparrows. In multiple experiments, infected sparrows did not transmit the virus to healthy sentinel birds housed alongside them. Researchers believe the virus kills sparrows so quickly that there isn’t enough time for sustained bird-to-bird spread within a flock. This means sparrows function more as intermediate hosts than as long-term reservoirs. They can pick up the virus from infected waterfowl or poultry, carry it briefly, and potentially pass it to other species, but they don’t maintain circulating infections the way ducks do.
Why Sparrows Matter for Poultry and Wildlife
Sparrows mingle freely with both wild waterfowl and domestic poultry. They visit backyard chicken coops, feed alongside ducks at ponds, and forage in agricultural settings. This behavior creates a bridge between wild bird populations where H5N1 circulates naturally and the farm environments where outbreaks cause the most economic damage. Since 2002, H5N1 viruses have been isolated from dead tree sparrows in the wild, and some of those isolates turned out to be highly pathogenic to chickens.
From an ecological standpoint, large-scale outbreaks could also threaten local sparrow populations directly. With fatality rates approaching 97% to 100% in some experimental infections, a severe outbreak moving through a dense sparrow population could cause significant die-offs, though this has not been widely documented in the field at a population level.
Risk to People From Infected Sparrows
The CDC lists sparrows among the common backyard birds in which avian influenza A viruses have been found. However, human infections from any wild bird remain rare and almost always involve prolonged, close, unprotected contact with infected animals. The general public risk from bird flu remains low. Most documented human cases worldwide have been linked to direct handling of infected poultry or visits to live poultry markets, not casual exposure to songbirds at a backyard feeder.
If you find a dead or visibly sick sparrow, avoid handling it with bare hands. Use gloves or a plastic bag to pick it up, and report clusters of dead birds to your state wildlife agency, which tracks potential avian influenza activity in wild bird populations.