What Diseases Can Humans Get From Chickens?

Chickens transmit a surprisingly wide range of infections to people, from common foodborne bacteria like Salmonella and Campylobacter to rarer threats like avian influenza and psittacosis. Some of these diseases come from eating undercooked meat or eggs, others from breathing contaminated dust in a coop, and still others from handling live birds or their droppings. The risks look different depending on whether you raise backyard chickens, work in a poultry facility, or simply cook chicken at home.

Salmonella and Contaminated Eggs

Salmonella is probably the first pathogen people associate with chickens, and for good reason. One particular strain, Salmonella Enteritidis, is especially adept at colonizing the reproductive tract of laying hens and depositing itself inside the edible portions of developing eggs before the shell even forms.¹ That means even eggs with intact, uncracked shells can carry the bacteria internally. Research into how S. Enteritidis pulls this off has shown that specific features of its outer surface are essential for surviving inside the egg’s albumin and colonizing the hen’s oviduct in the first place.²

In practical terms, the contamination rate from any individual hen is low, but because a single infected bird in a flock can keep shedding the bacteria for weeks, the cumulative risk across a large egg operation adds up. Symptoms of salmonellosis in people range from a few days of diarrhea, cramps, and fever to severe dehydration that requires hospitalization, especially in young children, older adults, and people with weakened immune systems. Thorough cooking kills the organism, which is why runny eggs and undercooked poultry remain the classic risk factors.

Campylobacter and Gut Infections

Campylobacter is actually a more common cause of bacterial foodborne illness than Salmonella in many countries, and chicken is its primary vehicle. Most people who pick it up experience gastroenteritis with diarrhea, abdominal pain, and fever. In a genomic study of human campylobacteriosis cases, gastroenteritis accounted for the overwhelming majority of clinical presentations, but certain genetic types of the bacterium were linked to Guillain-Barré syndrome, a rare but serious autoimmune condition that attacks the nerves.³ The connection between a common chicken pathogen and a potentially paralyzing neurological disorder tends to surprise people, but it is well-documented.

Campylobacter spreads mainly through undercooked chicken and cross-contamination in the kitchen. Unlike Salmonella, it does not typically multiply in food because it needs very specific growth conditions, but even a small dose can cause infection. Reducing colonization at the farm level has proven challenging. Competitive exclusion, where protective gut bacteria are given to young chicks to crowd out pathogens, can reduce both Salmonella and Campylobacter levels in the birds’ intestines, though the results under real-world farm conditions are more variable than in the lab.⁴⁵

E. coli and Urinary Tract Infections

This one catches most people off guard. When you think of E. coli from poultry, you probably think of food poisoning. But a growing body of research points to chickens as a reservoir for the types of E. coli that cause urinary tract infections, bloodstream infections, and even neonatal meningitis in humans. These strains are called extraintestinal pathogenic E. coli, and genetic studies have found striking overlaps between the strains that cause disease in poultry and those isolated from human UTIs.⁶

Multiple research groups have found that chicken and human E. coli strains share the same genetic lineages and virulence factors. Studies in both Canada and Brazil have identified overlapping genetic types circulating in poultry and in human clinical infections.⁷ One prominent genetic lineage found in both poultry and humans has been linked to UTIs, neonatal meningitis, and sepsis, and researchers have concluded that its virulence features are essentially indistinguishable between bird and human isolates.⁸ The exact transmission route from chicken to human UTI is still debated, but the genetic evidence is strong enough that some researchers advocate for a “One Health” approach treating poultry E. coli as a direct public health threat.

Psittacosis From Breathing Poultry Dust

Psittacosis is a respiratory infection caused by Chlamydia psittaci, a bacterium shed in the droppings, feathers, and respiratory secretions of infected birds. The name comes from parrots (psittacines), but chickens, turkeys, and ducks carry it too. You catch it by inhaling dried, aerosolized bird droppings or dust contaminated with the organism.⁹ Symptoms usually start like a bad flu, with fever, headache, and a dry cough, and can progress to pneumonia if untreated.

Poultry workers are the group at highest risk, and historical outbreaks in processing plants have underscored the need for better workplace controls and awareness.¹⁰ Psittacosis responds well to antibiotics when caught early, but it is often misdiagnosed as community-acquired pneumonia because doctors do not always ask about bird exposure. If you develop pneumonia-like symptoms and you work around poultry or keep backyard chickens, mentioning the bird contact to your doctor can make a real difference in how quickly you get the right treatment.

Avian Influenza and Why It Worries Public Health Officials

Avian influenza, particularly the H5N1 subtype, has been on public health radar for decades. The virus circulates widely in poultry flocks around the world and occasionally jumps to humans, usually through direct contact with infected birds or their environments. The reason it does not spread easily between people comes down to how avian flu viruses attach to cells: bird-adapted viruses preferentially latch onto receptors found deep in the human lung rather than the upper airway, making person-to-person transmission inefficient.¹¹

The worry is that this could change. Some H5N6 viruses have already acquired the ability to bind to receptors in human upper airway cells.¹² And when avian and human flu viruses co-infect the same host, particularly pigs, they can swap gene segments and produce hybrid viruses. Laboratory experiments have shown that reassortment between avian H5N1 and human H3N2 viruses can produce hybrids with dramatically increased virulence in mice.¹³ Mutations in a single protein subunit of the viral copying machinery can be enough to overcome the species barrier and allow an avian polymerase to work efficiently in human cells.¹⁴

The situation is made more dangerous by the co-circulation of multiple avian flu subtypes on the same farms. In Egypt, for instance, the simultaneous presence of H5N1 and H9N2 viruses in poultry populations has already led to the emergence of novel reassortant viruses carrying gene segments from both, some with mutations associated with increased virulence and adaptation to mammals.¹⁵ This is why global surveillance of avian influenza in poultry populations is considered one of the most important pandemic preparedness activities. There are proposals to expand existing surveillance networks into full One Health frameworks that link human clinical data with animal-health and environmental monitoring programs.¹⁶

Newcastle Disease Virus and Eye Infections

Newcastle disease is devastating to poultry flocks but generally poses only a minor risk to human health. It spreads readily among birds through respiratory droplets, and transmission risk increases with flock density.¹⁷ In people, the main documented illness is conjunctivitis, an eye infection that causes redness, tearing, and swelling. Outbreaks have been recorded among workers in chicken-broiler factories, typically affecting those who handle live birds or work near them without eye protection.¹⁸ The infection is self-limiting and resolves without treatment in most cases, but it is unpleasant enough to be worth knowing about if you handle poultry regularly.

Histoplasmosis From Chicken Manure

Histoplasmosis is a fungal lung infection caused by Histoplasma capsulatum, an organism that thrives in soil enriched with bird droppings. Chicken manure is an ideal growth medium because of its high nitrogen and phosphorus content.¹⁹ You do not catch it from the chickens themselves but from inhaling fungal spores kicked up when you disturb accumulated droppings, clean out a coop, or spread composted chicken litter.

Most infections are mild or go unnoticed entirely, producing flu-like symptoms that resolve on their own. But in people with compromised immune systems, histoplasmosis can disseminate throughout the body and become life-threatening. If you are cleaning a coop that has had chickens for years and the litter is dry and dusty, wetting it down before disturbing it and wearing a respirator are simple precautions that reduce spore inhalation considerably.

Toxoplasma in Undercooked Chicken

Toxoplasma gondii is usually associated with cats, which are the parasite’s definitive host. But chickens, especially free-range and backyard birds that forage on the ground, pick up the parasite from soil contaminated with cat feces and carry tissue cysts in their muscles. A Spanish study detected T. gondii DNA in retail meat from free-range chickens, confirming that eating undercooked poultry from these birds is a potential route of infection.²⁰

The difference between indoor and outdoor birds is stark. A Romanian seroprevalence study found that backyard chickens had roughly twice the exposure rate of intensively raised broilers, and at higher antibody levels the difference was more than tenfold.²¹ For most healthy adults, toxoplasmosis is either asymptomatic or causes mild, flu-like illness. The serious concern is for pregnant women, where primary infection can cause birth defects, and for immunocompromised individuals. Cooking chicken to a safe internal temperature eliminates the parasite.

Backyard Chickens and Pet-Like Contact

The rise of backyard poultry keeping has created a new exposure pattern that public health agencies are still catching up with. In a Massachusetts survey, over three-quarters of owners reported considering their backyard chickens pets, and their behavior reflected it: cuddling, kissing, and allowing birds inside the home.²² This kind of close contact increases the chance of picking up Salmonella, Campylobacter, E. coli, and other pathogens that healthy-looking birds can shed without showing any symptoms.

Children are at particular risk because they are more likely to put their hands in their mouths after handling birds and less likely to wash them thoroughly. Basic hygiene measures go a long way: wash your hands immediately after handling chickens or anything in their environment, keep birds out of the kitchen and living spaces, do not eat or drink in the coop area, and supervise young children around the flock. None of this means you cannot enjoy keeping chickens, but treating them like indoor pets carries real risk.

Occupational Respiratory Disease in Poultry Workers

People who work in poultry barns face a less obvious category of health risk: chronic exposure to organic dust. The air inside a chicken house is a cocktail of dried fecal particles, feather fragments, feed dust, and microbial compounds. A study of poultry farms found that workers had high rates of both asthmatic symptoms (about 43%) and nasal symptoms (about 51%), and that the duration of exposure predicted the severity of obstructive lung disorders regardless of whether the person smoked.²³

One specific condition to know about is organic dust toxic syndrome, which occurs when a person inhales a large dose of organic dust and develops an acute inflammatory response with fever, malaise, and chest tightness, somewhat like a sudden flu.²⁴ Unlike psittacosis, which is caused by a specific bacterium, organic dust toxic syndrome is triggered by the dust itself and the mix of bacterial toxins it carries. It does not require sensitization, meaning it can hit even first-time workers. Proper ventilation, dust reduction, and respiratory protection are the main defenses.

Antibiotic Resistance Traveling From Farm to Clinic

Beyond the diseases themselves, chickens are part of a broader public health concern around antibiotic resistance. The routine use of antibiotics in poultry production has accelerated the evolution of resistant bacteria, and those resistance genes do not stay on the farm. A metagenomic study of chicken gut bacteria in China detected genes conferring resistance to antibiotics considered last resorts in human medicine, including those effective against some of the most dangerous hospital-acquired infections.²⁵ Colistin-resistance genes, which compromise one of the final options for treating multidrug-resistant infections, have been found at high prevalence in E. coli from diseased chickens.²⁶

This matters because resistant bacteria from poultry can reach humans through direct contact, through the food supply, or through environmental pathways like manure runoff. When a person gets a UTI or bloodstream infection with a resistant strain, treatment options narrow and outcomes worsen. The connection is not hypothetical: the genetic lineages that link chicken and human E. coli, discussed earlier, carry resistance genes alongside their virulence factors. Reducing unnecessary antibiotic use in poultry production is one of the most actionable steps for slowing this cycle.

Kitchen Cross-Contamination

Even if you never set foot on a farm, you interact with potential chicken-borne pathogens every time you prepare raw poultry. The most common mistake is washing raw chicken before cooking it. The FDA recommends against this, and experimental work has confirmed the reason: water splashing off raw chicken can launch bacteria-carrying droplets across kitchen surfaces.²⁷ Changing the water pressure or the angle of the stream can make this better or worse, but none of the conditions tested eliminated the risk entirely.

Cross-contamination during preparation is the other major pathway. When researchers simulated a typical home cooking scenario, Salmonella from raw chicken transferred to cutting boards, knives, and hands, and then onward to a vegetable that was prepared on the same surface afterward.²⁸ The contamination level on the vegetable was low, but Salmonella’s infectious dose is also low, particularly for vulnerable people. The fix is straightforward: use separate cutting boards for raw meat and ready-to-eat foods, wash hands and utensils with soap between tasks, and cook chicken to an internal temperature high enough to kill pathogens (generally 74°C / 165°F throughout).

Sentinel Chickens and Mosquito-Borne Disease

In an interesting twist, chickens play a role in protecting human health from diseases they do not actually transmit. In parts of the United States, public health agencies keep flocks of “sentinel chickens” at strategic outdoor locations and regularly test their blood for antibodies to mosquito-borne viruses like West Nile virus and Eastern equine encephalitis virus. When a sentinel chicken tests positive, it signals that the virus is circulating locally, giving mosquito control programs an early warning to ramp up targeted spraying before human cases appear.²⁹ Chickens are useful for this because mosquitoes readily feed on them, the birds develop detectable antibodies without getting sick, and they do not produce enough virus to infect other mosquitoes and confuse the surveillance data. Florida’s sentinel chicken program has been refined over the years using spatial modeling to identify optimal coop locations where virus detection is most likely.³⁰ It is one of those quiet public health tools that most people never hear about.