Conditions Bird flu (avian influenza)

Bird flu is a viral infection that primarily affects birds. Specialists also refer to the disease as avian influenza. The pathogens are certain influenza A viruses, which can also be transmitted to humans in rare cases. Those affected tend to have close contact with poultry, for example due to working on poultry farms, breeding and fattening farms or in slaughterhouses.

There are two variants of bird flu that differ in terms of the level of disease they cause in poultry. Infections with the mild variant only cause mild symptoms, especially in domestic poultry such as ducks or geese. The highly pathogenic variant, on the other hand, causes serious illness in poultry and many wild bird species coupled with mass deaths. As a result, this severe form is also known as fowl plague. Both virus variants can be transmitted to humans and other mammals.

Influenza viruses affect several animal species, such as pigs and horses. They can also cause seasonal flu in humans. Normally, viruses are only transmitted within a single species. If a human contracts a flu virus that has its origins in the animal kingdom, this is known as a zoonotic influenza. Bird flu viruses can cause very serious illness in humans.

Bird flu in humans is a notifiable disease: even suspected cases have to be reported to the public health authorities. The genetic information of influenza viruses is able to mutate and new variants can emerge that can sometimes trigger a worldwide influenza pandemic. 

The outlook of bird flu can differ greatly: both asymptomatic and fatal forms exist. The initial symptoms generally appear 1 to 5 days after infection, but sometimes only 14 days later.

People who have been infected usually develop a high temperature and respiratory issues such as coughing and a shortness of breath. Nausea, vomiting and diarrhea are also possible. Other flu-like symptoms such as a sore throat, headache and achy limbs are rarer with bird flu than with seasonal flu.

Bird flu is caused by influenza A viruses, various subtypes of which are found in both animals and humans. Influenza viruses are classified based on two groups of proteins: hemagglutinin (H proteins) and neuraminidase (N proteins). Bird flu viruses that can currently be transmitted to humans largely fall into subtypes H5N1, H5N6, H7N9 and H9N2.

In nature, influenza A viruses are primarily found in wild waterfowl. As birds become infected via droppings, the viruses can also be transmitted to domestic poultry. Mildly pathogenic virus types spread rapidly without the birds developing clear symptoms of an infection. However, there are also highly pathogenic variants within the subtypes H5 and H7, which can lead to mass deaths, especially of chickens and turkeys but also of certain wild bird species.

Both virus variants can cause serious illness in humans. Other mammals can also contract the viruses. For example, pigs, cows, dogs, cats, foxes, otters and seals. Infections are primarily caused by close contact with infected birds and their droppings. It is also possible to contract the viruses through close contact with infected dairy cows. Transmission occurs through the inhalation of dust particles that contain the virus or as a smear infection via the hands. In the case of infected dairy cows, unpasteurized milk is the main transmission medium. Most cases affect people outside Europe who work on poultry farms, in poultry markets, on dairy farms or in slaughterhouses. Very few cases of human-to-human transmission have been recorded to date.

To date, there have been no recorded cases of bird flu in humans in Germany. Despite this, repeated cases of highly pathogenic, subtype H5 influenza A viruses have been recorded in poultry and wild birds in recent years. Accordingly, infection is also possible in Germany as wild birds can carry the viruses year-round. 

There is also an increased risk of contracting bird flu when coming into contact with poultry while traveling. Bird flu is found in many countries around the world. Recently, there have been ongoing outbreaks of bird flu among dairy cows in the USA. There have also been isolated cases of people becoming infected although they only experienced mild cases of the condition.

As people with mild flu symptoms are not usually closely examined, the actual number of people who contracted bird flu may actually be higher than that recorded.

For up-to-date information about the various infectious diseases occurring in countries outside Germany, see the Federal Foreign Office (Auswärtiges Amt) website.

A bird flu infection with the subtypes H5N1 and H7N9 may cause serious symptoms in humans. About half of the people who are hospitalized with the condition die. This is often as a result of multiple organ failure. In addition, the viral infection damages patients’ immune systems so much that bacteria can cause additional infections (superinfections) and further weaken the body. 

People who survive bird flu often suffer from permanent lung damage. Long-term kidney damage is also possible.

To prevent bird flu, people should avoid direct contact with diseased birds (dead or alive). Anyone who finds a dead wild bird should report it to the responsible veterinary office and not touch it.

People who work with poultry should observe the applicable occupational health and safety measures and implement appropriate hygiene measures. Any suspected bird flu infection in poultry must be reported to the competent veterinary office without delay.

Several vaccines for the prevention of bird flu have been approved for use in Germany. As the risk of infection within the general population is currently (as at 2025) low, these vaccines are only used for people whose profession puts them at risk, for example those who work in research institutions.

Anyone planning a trip abroad can contact the Federal Foreign Office to find out exactly where and in what situations there is a heightened risk of infection. Whether in high-risk areas or not, it is sensible:

• not to visit animal and poultry markets
• only to eat well-cooked poultry and eggs
• to thoroughly wash the hands with warm water and soap after preparing poultry
• not to consume unpasteurized milk or unpasteurized dairy products

A high temperature and respiratory symptoms are not definitive indications of flu or bird flu. To make a definitive diagnosis, evidence of the viruses is required. In the case of respiratory symptoms, having returned from high-risk areas or come into contact with poultry in a professional capacity may indicate bird flu. 

To diagnose the condition, a doctor takes a nasopharyngeal swab (a swab of the throat and nose). In practice, this material can be directly used to perform a rapid test. However, this will only provide evidence of a general infection with influenza viruses and is relatively insensitive. To determine the existence of bird flu, a lab test must be performed to assess whether the sample material contains the virus’s genetic material (PCR test).

Bird flu in humans can be a serious condition. It is therefore useful to prescribe medication that specifically combats the viruses. Treatment with antiviral medication such as oseltamivir or zanamivir should be initiated at an early stage, ideally within the first 48 hours of the suspected contact with the pathogen. 

It also helps to take antipyretic (fever-reducing) painkillers and drink plenty of fluids. Patients who are hospitalized are often given fluid intravenously. 

If pneumonia develops, patients are given additional oxygen. Mechanical ventilation is sometimes necessary. Seriously ill patients must then be monitored in an intensive care unit.

The Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung – BfR) provides information about recommended food hygiene measures and how consumers can protect themselves against bird flu.