March 21, 2025, 8:56 pm | Read time: 9 minutes
The “bird flu virus” H5N1 has been an issue for years. This is because it has the potential to trigger a new global pandemic. To date, there has been no known case of the virus being transmitted from person to person. However, new indications suggest that the virus is mutating and can be transmitted from humans to animals. This has alarmed American researchers. When asked by FITBOOK, an expert from Germany also considers the situation to be serious.
The rapid spread of the highly infectious avian influenza virus H5N1, also known as “bird flu,” has reached “unprecedented” levels, killing hundreds of millions of birds worldwide and increasingly spreading to mammals, warns the UN Food and Agriculture Organization (FAO) in a recent statement.1 In the first months of 2025 alone, around 166 million birds (mainly laying hens) had to be slaughtered worldwide. This also caused shortages in the supply of eggs. However, it is more important to protect people who could be infected with the virus.
According to the World Health Organization (WHO), more than 2,600 cases and 1,100 deaths from H5N1 have been confirmed worldwide since 2003, as reported by the Robert Koch Institute (RKI).2 And the number of unreported cases is likely to be much higher. Due to new mutations and the transmission of the bird flu virus from humans to animals, the probability of a new pandemic is growing, as reported by American researchers. How immunologist Prof. Dr. Carsten Watzl assesses the current situation is also revealed below.
Overview
What Is “Bird Flu”?
The H5N1 virus is known by several names, the most common being “bird flu” or “avian influenza.” It is caused by type A influenza viruses, which is why it is also known as “avian influenza.” Birds are usually the carriers, which leads to the corresponding name. The viruses, which are not very contagious, are usually found in the gastrointestinal tract or respiratory tract. The affected birds themselves contract the disease only mildly or not at all. It is assumed that if domestic poultry (not just wild birds) become infected, the viruses mutate more aggressively. This can, therefore, spread more widely.
How Do the Animals Become Infected?
It is assumed that transmission to domestic poultry occurs when animals come into contact with the droppings of infected birds or when the viruses can settle in the animals via their mucous membranes.3 Mammals can also become infected with H5N1 after coming into contact with infected birds, poultry, or their droppings. So far, it has mainly affected carnivorous wild animals, which presumably became infected from dead wild birds. In 2024, however, there were also outbreaks in dairy cow herds for the first time, as reported by the RKI.
How Do Humans Become Infected?
Transmission from animals to humans also occurs through direct contact with infected animals or their excrement, as explained by the Austrian Federal Ministry of Social Affairs, Health, Care and Consumer Protection.4 This mainly happens when the viruses get into the eyes, nose, or mouth. Inhalation can also lead to infection.
It has not yet been clarified whether the virus, found in raw foods such as eggs, raw milk cheese, and fresh milk, is contagious through consumption. However, a March 2025 study (not yet independently verified) detected the virus at least in raw milk cheese and provided evidence that H5N1 may be able to survive the cheese-making process.5 A CNN report states that there have been no confirmed reports of people falling ill from eating food contaminated with bird flu, including raw milk cheese. However, dairy workers have become infected by getting raw milk on their faces or in their eyes. Apparently, it also depends on the dose, i.e., the number of viruses that people are exposed to. The more contaminated a food is, the higher the probability that it can still be infectious.
Therefore, to prevent infection with H5N1, consuming pasteurized dairy products and avoiding raw eggs or raw milk products is generally safer.
What Are the Symptoms in Humans?
The first symptoms usually appear in humans within seven days of infection. Avian influenza can have a mild or severe course and, in the worst case, can lead to death.
Mild Course:
- flu-like symptoms
- fever
- sore throat
- shortness of breath
- cough
Severe Course:
- Inflammation of the lower respiratory tract (e.g. pneumonia)
- conjunctivitis
- Bleeding from the nose or gums
- Diarrhea, vomiting and abdominal pain
- Inflammation of the brain
How Likely Is a Bird Flu Pandemic?
Opinions on a potential bird flu pandemic vary widely. Unlike the coronavirus pandemic, there is no evidence to date that the H5N1 virus is transmitted from person to person. A current assessment by the US Centers for Disease Control and Prevention (CDC) states that the risk of infection for the general population is low.6 However, people who work with potentially infected animals, such as in dairy or poultry farms, are at a moderate to high risk of becoming infected, according to the CDC. In general, however, the probability of becoming infected with the bird flu virus is very low.
The World Health Organization (WHO) is of a similar opinion.7 According to a statement from November 2024 and based on the information available, the global risk to public health from H5N1 viruses is low. The risk of infection for occupationally exposed persons is classified as low to moderate. Although human infections are to be expected due to contact with infected animals or contaminated environments, the impact of such infections on public health at a global level is currently low.
The Robert Koch Institute also reports that there is currently no evidence of continued human-to-human transmission of avian influenza viruses worldwide. According to the RKI, no human cases of H5N1 viruses have been reported in Germany to date. This is despite the fact that birds with H5 viruses are also circulating in this country.
Why Are Some Researchers Alarmed?
So far, the WHO has not raised the alarm that the virus can spread among humans. However, there are now over 2000 cases of humans contracting the virus from infected animals. What is dangerous is that such infections are very often fatal. The mortality rate is around 50 percent. This means that around one out of two infected people die.
Taking into account the current avian flu developments, the American Harvard Medical School asked scientists from the Massachusetts Consortium on Pathogen Readiness (MassCPR) about their pandemic assessment.8 The big question was: Are we on the cusp of a major outbreak of avian flu?
“With H5N1, some factors point to an increasingly risky and uncertain situation,” says Jacob Lemieux, an infectious disease specialist at Massachusetts General Hospital. Increased activity has continued for over a year. The infection is spreading via domestic and wild animals and is spreading more frequently to humans. “The number of human cases has risen sharply since last year, when the first outbreak occurred in cows,” explains Lemieux. Although there are no signs of human-to-human transmission so far, he sees the need to step up efforts to track the spread of infection at the national, state, and local levels.
“I Think We Are Living Next to a Volcano, …”
“I think we are living next to a volcano that may or may not erupt. But we need to prepare for the possibility of a pandemic,” warns researcher Jacob Lemieux. His colleague Jeremy Luban, Professor of Molecular Medicine, Biochemistry, and Molecular Biotechnology at the UMass Chan Medical School, is also concerned. “Last year, I surveyed influenza experts, and there was a huge range of responses. Some said that H5N1 has been circulating since the 1990s, so they don’t think there will be a pandemic. Others are extremely concerned that the virus has changed a lot and is spreading in new ways, which may give it new characteristics,” says Prof. Luban.
Assessment by Immunologist Prof. Dr. Carsten Watzl
So there are certainly experts in the USA who are concerned that bird flu could pose a greater threat — possibly even developing into a pandemic. What is the German view of the H5N1 situation? When asked by FITBOOK, Prof. Dr. Watzl gave the following assessment: “The bird flu virus is on the WHO list of possible pathogens that have the potential for a new pandemic. The current spread of bird flu must, therefore, be taken seriously. However, the risk to humans is currently still low. This is because the virus has not yet managed to spread from person to person. The bird flu virus in chickens and wild birds can be dangerous for humans (with sometimes fatal infections). However, if you stay away from sick or dead wild birds and do not work directly with farmed animals, there is no risk of infection.”
However, he is also keeping a close eye on the situation in the USA: “In my opinion, the spread in dairy cows in the USA should be better contained. Although this virus is less dangerous for humans — previous infections have mostly been mild — the fact that the virus multiplies in mammals also increases the risk that it will adapt more to humans and that human-to-human transmission could be possible at some point.”
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Would Germany Be Prepared With Vaccines?
Even though there have not yet been any human cases of bird flu in Germany, caution is still called for. It is advisable to take protective measures, especially if you work in close contact with poultry or farm animals that may be infected. This can minimize the risk of transmission to humans. After all, the global community is keeping an eye on the spread of the bird flu virus.
Prof. Dr. Watzl is pinning his hopes on vaccinations and better preparation for a possible bird flu pandemic than was or could be the case with the coronavirus pandemic. “Influenza viruses are not as new as SARS-CoV-2. There are already vaccines against H5N1, but these would probably need adaptation if the virus becomes a pandemic. There is also hope that there is some cross-immunity from previous influenza infections and vaccinations. However, here, too, we need to see how much this could protect against a pandemic virus. But in terms of spread and protective measures, we are probably better prepared than we were for SARS-CoV-2, although there is certainly room for improvement,” says the immunologist.
According to the Association of Research-Based Pharmaceutical Companies in Germany (vfa), the first vaccines against H5N1 have already been developed. Further vaccines, including mRNA-based vaccines, are in development, reports the Deutsches Ärzteblatt.9 However, Germany has not yet ordered any of these vaccines. This is only done “in the case of an existing or imminent threatening communicable disease,” explained the Federal Ministry of Health. As the risk of an avian flu pandemic is currently low, no vaccines are currently being stockpiled.