Avian influenza is also known informally as bird flu or avian flu. In simple words, Avian influenza means influenza caused by viruses adapted to birds. The virus which is also called an Influenza A or Type A mostly lives in the birds but sometimes human beings or mammals are also infected with it. When it is transmitted to humans then it is called influenza. Generally, Aquatic wild birds have been a natural reservoir for a wide range of influenza A avian influenzas and they are the most common cause of influenza viruses in humans. These viruses are divided into several types, high and low pathogenicity, depending on what kind of impact they have on infected avian species. There has been a reported outbreak of avian influenza many times in different places around the world. Millions of birds have died as a result of infection or from slaughtering undertaken to control the infection. There have been rare incidents of an outbreak among humans.
The first reported case of Avian Influenza was recorded in a bird in Italy in 1878. Spanish flu, a type of bird flu killed 50 to 100 million people in 1918-20. Flu called Asian flu killed one million in 1957. Similarly, Hong Kong Flu had killed one million people in 1968. A subtype known as H5N1 killed six people in Hong Kong in 1997. It was found in the south-east of Asia and also spread to Africa and Europe until 2005. Influenza A is adapted to birds specifically but there is the possibility of it adapting to transmission from person to person. The recent Spanish flu virus research showed that it had genetic components adapted from both human and avian strains. So basically, there are two forms of risk to the health of humans from this virus. The first risk is that there is a possibility of infection by the native form of the avian influenza virus. The second risk is that there are chances of emergence of new pandemic strains directly from avian viruses. Recombination with human or other animal viruses is also possible which can also be very threatening. Even though there have been rare cases of H5N1 affecting humans but the most serious thing about it is that, it is evolving at a very fast speed and soon it may become a worldwide threat causing millions of human death.
Some avian viruses cause only mild symptoms like mild fever and they do not cause serious threat on humans. But avian viruses like H5N1 can be very dangerous causing serious diseases. During regular surveillance, if avian influenza viruses of the H5 and H7 subtype is detected in poultry farms, then it should be reported immediately. In that case, immediate steps, including precaution is applied to stop Avian to human transmission. Avian influenza viruses are of many subtypes but 5 subtypes including H5N1, H7N3, H7N7, H7N9, and H9N2 have been known to affect humans so far.
Transmission of Avian Influenza A Virus
In most cases of human transmission, it has happened because of handling dead infected birds or from direct contact with infected fluids. It can also transmit through contaminated surfaces and droppings of the birds. The virus can easily transmit from birds to birds and major threat so far is on the poultry industry around the world but the transmission from bird to human is also possible. If the virus keeps on evolving and mutating in the same way it is doing so far then human to human transmission is not impossible in the future. Avian influenza is spread by contact with the infected birds and it is also spread through contaminated equipments. The virus lives in the secretions from the nostrils, mouth, and eyes of infected birds. It is also found in the bird droppings. The disease is not a airborne disease in itself though it is spread through airborne secretions.
Signs and Symptoms of Avian Influenza A Virus
There are various signs and symptoms related with Avian Influenza virus. The major symptoms are as follows:
- Low pathogenic avian influenza may cause symptoms like conjunctivitis, and influenza like conditions like fever, cough, sore throat, muscle aches. It may also cause lower respiratory disease or Pneumonia.
- Highly pathogenic avian influenza virus can cause symptoms like conjunctivitis only, influenza like illness, severe respiratory illness, pneumonia, acute respiratory distress, viral pneumonia, respiratory failure and multi-organ disease. Sometimes, there can also be problems like abdominal pain, diarrhea, nausea and vomiting and sometimes neurologic changes including altered mental status and seizures.
Diagnosis of Avian Influenza A Virus
Laboratory testing is necessary to diagnose Avian Influenza A Virus. It is not possible just with clinical signs. A swab from the nose or throat of the sick person during the first few days of illness is collected to diagnose the illness. The sample is tested in a lab to find the avian influenza A virus by a molecular test or by attempting to grow the virus. Collection and testing of lower respiratory tract specimens is done in case of critical patients. But it may be difficult to diagnose the virus in people who are no longer sick with these methods. Evidence of the body’s immune response to the virus infection can be checked by detecting specific antibodies the body has produced in response to the virus. But two different blood samples are required for this including one in the initial stages and one after 3-4 weeks.
Treatment in Humans
Oseltamivir, peramivir, or zanamivir are prescribed for the treatment of human infection with avian influenza A viruses. Antiviral resistance has been reported in some HPAI Asian H5N1 viruses and influenza A H7N9 viruses. Regular monitoring and studies related to anti viral treatment is going on. Different Governments and research institutes are spending millions of dollars to find out solutions to this potential threat to the world. They are trying to study about H5N1, creating vaccines, conducting pandemic practice exercises, stockpiling useful flu medication, and also many other important activities.
Preventive measures of Avian Influenza A Virus
There are many preventive measure related to Avian Influenza A Virus which can keep us safe from it. It should be specially noted and followed in our daily lives then only we can be protected from this illness. The most reliable way is to stay away from possible sources of this virus. Most cases of infections has been reported from infected poultry so it is advised to stay away from infected poultry to stay safe. People who work in poultry farms in close contact with the poultry and chicken have to be extra cautious when dealing with the birds. During times of outbreak of Avian influenza among the birds, the workers in poultry farms and people living in close proximity of that area should be extra careful. They must adopt an additional preventive measure to stay safe from undesirable conditions as a viral infection. Influenza antiviral drugs are administered to anyone who comes in contact with infected birds. Those anti viral drugs are used for treatment and also to prevent seasonal influenza. The antiviral drugs are 70% to 90% effective. Seasonal Influenza vaccine will reduce the risks of co-infection with human and avian influenza A viruses. The vaccine against Avian Influenza can also be made. The US government is reported to maintain a stock of vaccine which can be used if the H5N1 virus starts transmitting from person to person.