The pathogens causing avian influenza belong to the influenza virus strain and some of them can also be dangerous to humans. The disease was first observed as “European avian influenza” in Italy in 1878. After major waves of infection in Germany in 2006 and 2009, isolated cases of a new virus type (H5N5) have been detected since November 2016, particularly in Lower Saxony.
What is bird flu, anyway?
Avian influenza, also known as bird flu or, in technical terms, avian influenza, is a worldwide infection transmitted by viruses that primarily affects chickens, turkeys and ducks, but less commonly wild birds, pheasants and guinea fowl. In common parlance, “avian influenza” refers to the subtypes of the virus that are transmissible from animals to humans. The disease can be transmitted from animal to animal, through feces and, especially in wild birds, through the respiratory air, and is fatal for 80 to 100 percent of affected animals. The disease breaks out in poultry about three to 14 days after infection. Symptoms in affected birds include:
- High fever
- Breathing problems
- Reluctance to eat and dullness
- Diarrhea
- Discharge from eyes and beak
If an animal is sick, it can die within a few hours to days. The risk of infection for other animals in the group is high.
Bird flu: danger for humans?
For humans, most types of avian influenza viruses are generally not dangerous. However, mutations, as in the case of virus subtypes H5N1, H7N9 or the H5N5 pathogen, can cause humans to become infected in animals. Once infected, such a virus can cause severe illness similar to pneumonia. In some cases, such an infection with the avian influenza virus can even take a fatal course.
Transmission of avian influenza to humans
Because virus types H5N1 as well as H7N9 are particularly aggressive, infection is more likely with these pathogens than with others. Worldwide, around 600 deaths related to the H7N9 subtype alone occurred between 2013 and 20118. So far, experts assume that transmission occurs directly from infected poultry to humans via feces and blood splatter, but most likely not through the consumption of infected meat. Nevertheless, meat and eggs should only be eaten well-done or cooked to be on the safe side. Dead wild birds should not be touched, also for hygienic reasons. The former also explains that transmissions to humans occurred primarily in Asia: On the one hand, people there often live very closely together with poultry, and on the other hand, it is common to offer and prepare chickens very fresh shortly after slaughter on the market. According to the WHO, in Southeast Asia it was mainly people who had contact with the animals during slaughter, plucking or cooking who became ill. Human-to-human transmission has only been suspected in isolated cases, but this has not been scientifically proven. Cats can become ill by eating an infected bird, but transmission of the virus from cats to humans has not been reported.
What are the symptoms of infected humans?
Infection with avian influenza can manifest in humans in a variety of ways. The spectrum ranges from cases with no signs of illness to a fatal course, often due to pneumonia triggered by the virus. Symptoms such as fever, cough, and chills are similar to those of a normal flu or severe cold. If infection with avian flu is suspected, a doctor should be sought immediately and contact with other people should be avoided for their protection. Possible symptoms of avian flu include:
- High fever
- Cough (until shortness of breath)
- Sore throat
- Diarrhea
- Less frequently vomiting and stomach pain
Diagnosis of avian influenza
The symptoms of avian flu are similar to those of influenza or a strong flu-like infection. So in the conversation, you should point out to the doctor if there has been close contact with possibly infected animals or their feces, respectively, or if undercooked meat has been consumed. To determine the pathogen, nasal and throat secretions or bronchial secretions are examined for pathogens using a real-time PCR method.A blood test can also provide information. This often reveals a deficiency of white and red blood cells as well as platelets.
Treatment of avian influenza in humans
If infected with one of the virus types, flu medications may be given to relieve symptoms. Pain medications may also help. Antivirals, or virus-killing drugs, are used against the viruses themselves.
Preventing an infection with bird flu
Anyone who wants to be completely safe during an outbreak should avoid poultry markets and poultry farms. Also, anyone who finds sick or dead birds should never touch them, but should immediately inform the appropriate veterinary office. There is no need to be afraid of pigeons in public areas, they are extremely rarely affected by avian influenza. In contrast to normal influenza, the incubation period for avian influenza is only two to eight days, but can also be up to 14 days. Therefore, it is imperative to avoid contact with infected individuals to prevent infection. After detecting an infection with the avian influenza virus, it should be clarified with a physician whether the infected person should observe a quarantine.
Hygiene rules when handling poultry meat.
Food that has been cooked or otherwise heated is considered free of disease-causing virus. However, freezing does not inactivate the virus. In this context, it is therefore worth pointing out the most important hygiene rules when handling poultry meat:
- Poultry meat should always be well cooked (above 70 degrees Celsius).
- All work surfaces and kitchen utensils that have come into contact with raw meat must be rinsed well – preferably under running water.
- Wiping and rinsing cloths that have come into contact with raw meat, it is best to always replace directly.
Spread of avian influenza among domestic poultry.
The probability of transmission of the highly pathogenic virus species by migratory birds to domestic poultry by direct route is considered rather low. More likely is natural, slow virus spread through overlapping breeding areas of ducks. However, during disease outbreaks, it is especially important to raise public awareness of the risk of virus introduction. Attempted illegal poultry imports, smuggling of songbirds, or unknowing introduction of the virus pose the greatest risks for spread.
Poultry farmers on alert
In the event of an outbreak of avian influenza among poultry, all measures specified in the Avian Influenza Ordinance will be initiated. These include in case of disease outbreak:
- Entry bans
- Movement bans
- Immediate killing and destruction of the poultry
- The establishment of restricted areas and observation areas
Vaccine against avian influenza?
Vaccination for poultry to protect against avian influenza exists, but is controversial. While live vaccines carry the risk of mutation of the viruses, inactivated vaccines pose the risk that vaccinated animals may not show symptoms, but still spread the virus. No vaccine currently exists for humans. Influenza vaccination may be useful to avoid simultaneous infection with the normal influenza virus and avian influenza.
Mutation of viruses – the big concern
Of concern is the possibility that bird flu viruses could combine with a conventional flu virus to form a new pathogen. Such a pathogen – directly dangerous to humans (“human pathogenic”) – could be transmitted from person to person, posing the risk of a major epidemic. Pigs and horses could also be hosts in which new virus strains could develop. Currently, however, this risk does not exist.
Conclusion: dangers from avian influenza to humans rather low
Sufficient safety precautions are currently in place in Germany to prevent or contain any waves of avian influenza that may occur. The risk of transmission of the virus from birds to humans is generally very low. Nevertheless, if someone is infected with one of the various avian flu pathogens, this can usually be treated well today.
