Bird flu has spread in recent years around the world, causing many right and wrong fears. So what is this disease that massively kills breeding birds and incidentally causes scent of poultry farmers?
Viral bird disease ...
Avian influenza is a viral infectious disease of birds caused by certain strains of influenza A virus. It may be mild or abrupt and highly contagious. The mass incidence and mortality of birds depends on the type of virus that has infected the herd. The strain of influenza type A, designated H5N1, is particularly dangerous. All species of birds are susceptible to it, although some may be more resistant. Infection with this virus causes characteristic symptoms in the domestic birds, of which we write below, including a highly contagious and lethal form of the disease causing massive epidemics and the fall of birds in broilers and chicken houses. The latter form is known as "highly pathogenic avian influenza". The course of the disease depends on whether the birds were attacked by the avian flu virus with low virulence so-called LPAI causing disease with less severe symptoms and giving lower losses in breeding, or by the virus of high virulence so-called. HPAI causing the death of nearly 100% of infected birds.
H5N1 virus - a killer of birds
Let's introduce the most dangerous bird flu virus, marked H5N1. This virus is characterized by high virulence, i.e. the ability to kill infected organisms. Its original reservoir is wild birds - wild ducks, peregrine falcons, quail, pheasant, etc. The H5N1 virus can spread to domestic fowl through feces, as well as wild bird secretions. It attacks cyclically every several - several years, most often in Asia, which is its backwoods. The virus is infected by direct contact between birds, which is why the infection spreads very quickly on poultry farms, where the high density of birds is particularly conducive to the transmission of viruses. The epidemic usually affects popular species of domestic fowl - mainly hens and ducks, but also geese, turkeys and guinea fowl. Influenza viruses that develop in breeding birds are slightly different and may - albeit not - be highly pathogenic and toxic to humans (virulent).
Symptoms of bird flu in birds
The first symptoms of the disease in poultry are diarrhea, reduced mobility and apathy. Later, you have breathing difficulties, swelling of the head and neck, and loss of consciousness. Sometimes birds start to fall suddenly without any previous symptoms of the disease, which indicates the spread of "highly pathogenic avian influenza" probably caused by the H5N1 virus. It's good to know that the symptoms of bird flu mainly depend on the strain of the virus that attacked the birds. In addition, they depend on the species of breeding bird, and above all on the type of breeding birds and their individual immunity. The least resistant to infection by the virus are birds bred in industrial methods, especially broilers that lack almost natural immunological immunity. The incubation time of the disease in a farm of breeding birds is from three days to a week.
Fight against the spread of bird infections
Highly pathogenic avian influenza viruses are quite resistant to external factors and can survive for a long time in the environment, especially at low temperatures. The H5N1 virus is killed only at temperatures above 70oC. The main measures preventing the spread of avian influenza is quarantine of birds on farms and aseptic for the surroundings, liquidation of infected or potentially infected domestic birds.
It threatens people's lives
H5N1 virus - the killer of birds is highly dangerous for humans, as it occasionally shifts to a man threatening his life seriously. The most endangered are people who are in direct contact with an infected bird - they are mainly poultry farmers. But the virus can also infect workers transporting sick poultry, vendors, cooks, hunters, etc. The first documented loss of human infection with the H5N1 avian influenza virus occurred in Hong Kong in 1997. At that time, 18 people fell ill, 6 of whom died. This coincided with the H5N1 bird flu epidemic among domestic fowls. It was found that the cause of disease in humans was close contact with live, infected poultry and infection with the avian virus. A quick liquidation of approximately 1.5 million poultry prevented the spread of the disease. In recent years, several new cases have been reported among Thailand and Vietnam. Unfortunately, there are now more and more cases of bird flu among birds throughout the world, including Russia and Europe (Turkey, Romania and Greece). Getting the bird flu to Poland seems only a matter of time.
How does a bird virus infect people?
Man is infected with avian influenza virus through direct contact with domestic fowl. A particular place of risk of infection are chicken farms and bazaars where live birds are traded. The avian influenza virus is transmitted to humans through direct contact with birds, their feces, meat, etc. Other ways of spreading are: infected equipment, vehicles, food or cages. Sometimes the virus can spread from wild birds, mainly to hunters. Although in the area where the birds are already infected, city pigeons are also at risk.
What is the mechanism of virus attack on the body
When any virus gets inside the human cell - it activates its aggressive genetic apparatus encoded in the structure of nucleic acids. Regardless of whether it is a "human" or "bird flu" virus - its nucleic acids subordinate to itself the genetic apparatus of the host cell. As a result of many transformations, new virus particles multiply (so-called replication) while destroying human cells. Infection in the body does more or less damage depending on the virulence of the virus and individual immunity. Not every human being infected with the bird flu virus will fall ill because some of us have a highly efficient immune defense.
Symptoms of bird flu in humans
Symptoms partly resemble "ordinary" human influenza, but they are much more violent. They are characterized by very high fever, muscle pain, coughing. In the case of H5N1 infection, more serious complications occur - pneumonia, as well as acute respiratory failure, which can lead to death. Statistically, about half of the documented cases of human disease ended up in the patient's death. Warning! The greatest threat is bird flu infection in children, the elderly and people with reduced immunity. Mortality approaches 100 percent in these groups.
Are Polish laboratories capable of detecting a bird flu virus?
Yes. According to Andrzej Trybusz - Chief Sanitary Inspector - the virology laboratories at the sanitary and epidemiological stations are well prepared to examine every sample of patients with symptoms of influenza. Isolated influenza viruses are sent to the National Influenza Center at the National Institute of Hygiene, where specialists are able to decide whether the infection has caused a human or a bird virus.
Is the epidemic of bird virus infection threatening the world and Poles?
There is no such threat for now. Until the virus has mutated, i.e. it did not acquire the property of easy transfer from one sick person to another - causing this disease to be life-threatening - WE WILL FEEL HIMSELF? RELIABLE SAFE! The epidemic of mass infections affects only birds. Since 1997, when the bird flu virus first attacked people in Asia, only a hundred tens of people have actually fallen ill. This proves that the bird virus type H5N1 has a small ability to move from birds to humans. No less individual illnesses are possible.Medical authorities believe that the danger of a massive outbreak of bird flu among humans is scarce, but it does exist! The bird virus may in fact become a deadly epidemiological threat when it mutates and will be able to move rapidly through the droplet from an infected person to a healthy person. And that can not be ruled out, and what's more, you have to prepare for it.
Can a vaccine against traditional flu protect against avian influenza?
No. Experts believe that the vaccine against traditional flu does not provide protection against avian influenza. Some of them believe that vaccination increases the chances of a milder course of infection and recovery.
Treatment of bird flu
In bird flu, the treatment is partly similar to the "normal" flu treatment. First, we treat the symptoms of the disease - inflammation, high fever, sore throat - the same anti-inflammatory and antipyretic drugs (ibuprofen, paracetamol, naproxen, acetylsalicylic acid, etc.) as the usual flu. Secondly, antiviral preparations are used to fight the virus.
Antiviral drugs
For a long time now, drugs known to have a virus-like effect have been known - inhibiting the reproduction (replication) of the influenza virus in the body. Some of them - eg for people allergic to traditional influenza vaccines - are effective against the avian influenza virus. For example, with the help of antibiotics containing amantadine and rimantadine, known for years, you can block intracellular metabolism. This blocks the first step in subordinating the genetic mechanism of cells to the virus. Stopping the multiplication of the virus in the host cells means stopping the flu infection or significantly reducing its severity. The problem is that viruses have the ability to change their structure and immunize against such drugs.
Warning! Amantadine does not fight the bird flu virus anymore ...
Amantadine has been recognized until recently as a drug capable of stopping (or significantly alleviating) the development of avian influenza virus type A - already after infection with a human being. Unfortunately, it turned out that the bird flu virus can be immune to this type of medicine. These fears were confirmed by Dr. Yi Guan from the University of Hong Kong who has been investigating the bird virus H5N1 in Asia since 1997. According to this researcher, when the bird flu invaded people in Hong Kong for the first time in 1997, it was amantadine that made it possible to control the epidemic quickly. However, a few years later, in 2003, when the virus hit again, this drug was already ineffective.
Hope in anti-viral drugs of the new generation
The preparations of zanamivir and oseltamivir are already available in Poland, these drugs that inhibit the development of influenza viruses in the body. They effectively destroy both A, B and avian influenza viruses. The condition for the effectiveness of treatment is to start therapy in the early phase of infection, ie within the first 48 hours from the onset of symptoms and continue it for 5 days. At the same time, these drugs can not be abused. Because scientists from the American Centers for Disease Control and Prevention in Atlanta warn that inappropriate and too frequent use of antivirals - for example oseltamivir - can make the influenza virus immune. Therefore, these medicines should not be substituted for influenza vaccines. The more so that the latest generation of antiviral drugs are many times more expensive than the vaccines. For example, one packet (10 tablets) now has to be paid over PLN 150. (Note: oseltamivir is only available on prescription)
Can the bird flu virus mutate in the future and be able to spread between people?
Such a risk always exists. All influenza viruses have the ability to quickly mutate. It is more likely to replace the genes of the avian virus in a triangle: birds, mammals, humans, which has already taken place and was the documented cause of the deadly pandemic. Perhaps, however, as a result of the mixing of human genes and avian viruses, a pathogen of avian influenza will arise that is capable of spreading rapidly between people and causing a pandemic. This is a scenario that sleeps with epidemiologists and ... us all. Fortunately, this is not a threat on a scale of weeks, but a risk spread over long months or years. In the meantime, it is a race against time to produce a human immunization vaccine for the most dangerous bird flu virus.
Is it possible to develop a vaccine against bird flu in humans?
Yes. Currently, many countries are working on several variants of immunizations against the H5N1 virus.There is high hopes (in molecular studies) that the ability of the bird flu virus to multiply in a human cell results from the presence of polybasic amino acids in its genome - in the so-called molecule. hemagglutinin. Substitution of H5N1 hemagglutinin virus molecular fragment with the gene transferred from the harmless H6N1 influenza virus (and connection with the rest of the microbial structure) - allows to obtain a modified virus that is non-infectious to chicken embryos and experimental animals. A big problem is the unusual variability of the genetic code of the H5N1 virus of avian influenza, which quickly obsoletes the effectiveness of the vaccine so obtained. However, the hitherto technological success - obtaining a modified virus particle within 4 weeks - brings closer the chance of preparing an effective vaccine against bird flu. The proof of this is the Hungarian pharmaceutical industry producing the first such vaccine that can protect birds against an epidemic, as well as people against the bird virus. One can hope that soon the next vaccines will appear and prove effective enough.
