Bird Flu

Bird Flu overview and Definition

Bird flu is also called as Avian(bird) influenza.Also called as Lambordian virus.Incubation period of bird flu h5N1 is two to five days. And for H7N9 the average incubation period is five days can last upto 10 days.

Structure of Bird Flu


It is an spherical shaped RNA viruses.They belongs to Orthomyxoviridae family and this family viruses are subdivided in type A,type B, type C based on their nuclear and matrix proteins. the Avain viruses belongs to the family Orthomyxoviridae. They consisted of segmented genome. They are roughly spherical with glycoprotein spikes on surfaces and genome consisting of eight RNA fragments that encode 10 proteins. The M1 protein which is the major determinant of virion morphology.The nucleoprotein (NP) associates with each RNA segment to form the ribonucleoprotein.The major proteins includes (HA) haemaglutinin,(NA) neuraminidase and matrix(M).The surface protein such as HA and NA are critical for the biology  of influenza virus.There are 16 haemagluttinin subtypes, 9 neuraminadase subtypes of influenza virus A. All viruses which causes the respiratory problems is mostly of H5 and H7.


The virus is concerned with the respiratory system and causes illness in it and decreases the immune activity of the cell.The HA plays an vital role in causing the disease.The pathophysiology mainly includes lung inflammation caused by immune responses.This inflammation can spread systemically and manifest as a multiorgan failure and results in severe respiratory distress.It also triggers Acute Respiratory distress syndrome.Gas exchange is obstructed.The soft palate is enriched in alpha 2,6 linked sialic acid which are preferably by the haemagglutinin proteins currently found in circulating human influenza viruses

Routes of Transmission

Avian influenza is most often spread by contact between infected and healthy birds, though can also be spread indirectly through contaminated equipment. The virus is found in secretions from the nostrils, mouth, and eyes of infected birds as well as their droppings. HPAI infection is spread to people often through direct contact with infected poultry, such as during slaughter or plucking. Though the virus can spread through airborne secretions, the disease itself is not an airborne disease. Highly pathogenic strains spread quickly among flocks and can destroy a flock within 28 hours; the less pathogenic strains may affect egg production but are much less deadly.

Although it is possible for humans to contract the avian influenza virus from birds, human-to-human contact is much more difficult without prolonged contact. However, public health officials are concerned that strains of avian flu may mutate to become easily transmissible between humans. Some strains of avian influenza are present in the intestinal tract of large numbers of shore birds and water birds, but these strains rarely cause human infection.

Five manmade ecosystems have contributed to modern avian influenza virus ecology: integrated indoor commercial poultry, range-raised commercial poultry, live poultry markets, backyard and hobby flocks, and bird collection and trading systems including cockfighting. Indoor commercial poultry has had the largest impact on the spread of HPAI, with the increase in HPAI outbreaks largely the result of increased commercial production since the 1990s.

Village poultry:

 the early days of the HPAI H5N1 pandemic, village poultry and their owners were frequently implicated in disease transmission. Village poultry, also known as backyard and hobby flocks, are small flocks raised under extensive conditions and often allowed free range between multiple households. However, research has shown that these flocks pose less of a threat than  raised commercial poultry intensively with homogenous genetic stock and poor biosecurity. Backyard and village poultry also do not travel great distances compared to transport of intensively raised poultry and contribute less to the spread of HPAI. This initial implication of Asian poultry farmers as one broad category presented challenges to prevention recommendations as commercial strategies did not necessarily apply to backyard poultry flocks.  

The following viruses plays a vital role in causing the infections in recent years:





Clinical signs & symptoms

  • cough
  • diarrheoa
  • respiratory difficulties
  • fever (over 100.4°F or 38°C)
  • headache
  • muscle aches
  • malaise
  • runny nose
  • sore throat

Differential Diagnosis

Specimen required:

The specimen is taken from the bird which is sick or dead from the cloacal region and  trachea and they are stored in transport medium. For dead birds 3 organs such as trachea,brain and digestive organs.Transport medium can be prepared with isotonic phosphare buffered saline and gentamicin sulphate.

The ELIZA and PCR test are used to detect the viral antigen.

For critically ill patients, collection and testing of lower respiratory tract specimens also may lead to diagnosis of avian influenza virus infection. However for some patients who are no longer very sick or who have fully recovered, it may be difficult to detect the avian influenza A virus in the specimen. Sometimes it may still be possible to diagnose avian influenza A virus infection by looking for evidence of antibodies the body has produced in response to the virus. This is not always an option because it requires two blood specimens (one taken during the first week of illness and another taken 3-4 weeks later). Also, it can take several weeks to verify the results, and testing must be performed in a special laboratory, such as at CDC.


The symptoms might seen mild but severe cases of bird flu results in dead.

For those patients hospitallized with avian flu the mortality rate is more than 50%

The mortality rate of H5N1 has been estimated to be 60% and H7N9 is around 40%



Several vaccines against different strains of avian H5N1 have been developed, but continual mutation of the virus means these are now ineffective. Some of these vaccines, however, can provide cross-protection against related flu strains but the only way to provide full protection is to develop a vaccine protective against a future pandemic strain. As there is currently no pandemic, no pandemic vaccine can be developed. Only pre-pandemic vaccines can be developed, tested and refined in the hope that they will help prepare for the next pandemic. Vaccine manufacturing companies have been encouraged to expand their capacity to enable quick production of large amounts of vaccine, should a new pandemic arises.

  • Hand washing, especially after going to the toilet and before handling food
  • Covering the mouth while coughing or sneezing
  • Disposing of tissues after use
  • Avoiding public places if you are ill
  • Ensuring a good level of general health and attending any vaccination appointments that have been recommended such as a seasonal flu jab.
  • Washing the hands after any contact made with wild birds when feeding them, for example.
  • Avoiding live animal markets or poultry farms if visiting an area where a bird flu outbreak has occurred.