A deadly outbreak of psittacosis, also known as parrot fever, is spreading across Europe, prompting a warning from the World Health Organization (WHO).

The WHO announced on Tuesday that parrot fever cases have been on the rise in several European countries since November 2023, resulting in five reported deaths to date.

In a disease outbreak notification, the global health agency highlighted recent cases in Austria, Denmark, Germany, Sweden and the Netherlands. In most cases, the infected people had been in contact with either a domestic or wild bird.

“This is one of those things where people who own pet birds should just be aware that this is a potential pathogen you can get from your pet bird,” infectious diseases specialist Dr. Isaac Bogoch told Global News. “But for the general community at this point in time, there’s really nothing to be concerned about.”

He mentioned that while there have been cases of psittacosis in Canada, they are exceedingly rare. And, if someone does contract it, the likelihood of death from the illness is also low.

“It’s something that’s being monitored and this was picked up because there are more robust surveillance systems in many parts of the world,” he said.

Parrot fever is a respiratory infection caused by the bacteria Chlamydia psittaci, commonly found in birds, according to Health Canada.

“It’s a distant relative to the chlamydia, the sexually-transmitted infection, but this is not a sexually-transmitted infection,” Bogoch said. “But from a genetic relative standpoint, it’s a cousin.”

It is a zoonotic disease, meaning although it primarily affects birds, can also infect humans who come into contact with them, their droppings, feathers, or respiratory secretions. This risk is particularly high for people in occupations involving birds, such as pet bird owners, poultry workers, veterinarians and gardeners.

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The bacteria, according to the WHO, is known to affect more than 450 bird species (with parrots being the most common carriers) and can also spread to other animals like dogs, cats, horses, cattle and reptiles.

Parrot fever is considered a rare disease, and its exact prevalence is not well-documented. However, according to Health Canada, human cases often happen sporadically.

It is also not a nationally notifiable disease in Canada, the health agency told Global News in an email sent on Wednesday.

If a bird is infected with psittacosis, common symptoms include poor appetite or weight loss, inflamed or runny eyes or nose, breathing difficulties and diarrhea.

Birds with latent infections may seem fine at first but could show symptoms later on, according to the Canadian Centre for Occupational Health and Safety (CCOHS).  Those carrying the bacteria also may intermittently shed it for weeks or even months.

In humans, it can cause pneumonia, Bogoch said.

“And like any other pneumonia, it can be serious. It’s kind of challenging to diagnose in terms of honing in that this is actually psittacosis, as a pathogen,” he said.

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If infected, the signs and symptoms appear within four to 15 days after exposure but commonly occur after 10 days. The most common symptoms in humans include fever and chills, headache, muscle aches and dry cough.

Parrot fever mainly affects the lungs but can also impact various organs, the CCOHS said. While uncommon, inflammation of the liver, pericardium (lining of the heart cavity), myocardium (heart muscle), and brain have been reported.

The disease’s progression varies, and while death is possible, it is rare. In mild cases, fever may persist for three weeks or longer.

While birds that carry this disease could be crossing international borders, there is currently no indication of this disease being spread by humans nationally or internationally, the WHO said.

Generally, people do not spread the bacteria that causes psittacosis to other people, so there is a low likelihood of further human-to-human transmission of the disease.

“It would be unusual to do that,” Bogoch said. “There’s so few cases of this and this is something that we look for from time to time. And then when there’s an appropriate epidemiologic exposure, but we rarely find it.” 

The disease is also not spread by eating infected animals, the CCOHS said.

Bogoch explained that the treatment approach for someone infected with psittacosis is largely similar to that for pneumonia, which is typically antibiotics.

“The conventional antibiotics are used to treat this that we typically treat community-acquired pneumonia,” he explained.

“So when someone comes into the hospital and they’re sick with pneumonia, we rarely make a microbiological diagnosis. When we treat pneumonia, we treat it as a syndrome.“

A health-care provider may sometimes send a sample to a lab to confirm a diagnosis of psittacosis, especially if the patient has a pet bird, he noted.

“So (psittacosis) may be more common than we know because we don’t look for it. And when we want to look for it, it takes a long time to get those diagnostic tests back,” Bogoch said.

While the cases are still incredibly rare, the WHO said the concerned countries have implemented epidemiological investigations to identify potential exposures and clusters of cases.

The increase in reported psittacosis cases across all countries “requires additional investigation to determine whether it is a true increase in cases or an increase due to more sensitive surveillance or diagnostic techniques,” the WHO added.

In Austria, 14 confirmed cases of parrot fever were reported in 2023, compared to the average of two cases per year in the previous eight years, according to the WHO.  In 2024, the country has reported four cases of the disease as of March 4.

Denmark reported an increase in parrot fever cases from late 2023 to mid-January 2024, the WHO said. As of Feb. 27, 23 individuals tested positive for the disease. Seventeen cases were hospitalized, of whom 15 had pneumonia and four died.

The National Health Institute of Denmark suspects that infections are primarily associated with wild birds through the inhalation of airborne particles from the dried droppings of infected birds.

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“It is assumed that the actual number of individuals infected with C. psittaci is much higher than reported,” the WHO said in the statement.

Germany reported an increase in individuals who tested positive for the bacteria in December 2023 with five confirmed cases, making a total of 14 confirmed cases in 2023. In 2024, as of Feb. 20,, another five confirmed cases of psittacosis were reported.

Sweden reported an unusually high number of cases of psittacosis in late November 2023 and early December 2023, with seven cases reported in November 2023 and 19 cases reported in December 2023. This represents a doubling of the number of cases compared to respective months in the previous five years, the WHO said. 

The WHO said it is continuing to monitor rising cases in Europe, though it deemed “the risk posed by this event as low.”