Bird Flu created a terror in the whole world. Not only that, the strain killed many people. All over the world, a mutated form of virus made world news. There were also no antibiotics or vaccines to cope with the menance, thats the reason, I though of giving you the details about the Avian Flu and also about its origin and it’s history. This will definitly help you to gain knowledge about the deadly virus.
Bird Flu is a subtype of the Influenza A virus. Its Influenza A Virus subtype H5N1, also known as A(H5N1) or H5N1. It is endemic in many bird populations, especuially in South East Asia. One strain of HPAI A (H5N1) spread globally after first appearing in Asia.
Before going into the details; let us define a virus. A virus is an microscopic particle that can infect the cells of a biological organisms. Viruses can only replicate themselves by infecting a host cell and therefore can not reproduce on their own. At the most basic level, viruses consist of genetic material contained within a protective protein coat called a capsid. They infect a wide variety of organisms; both eukaryotes(animals, yeasts, fungi and plants) and prokaryotes (Bacteria). Viruses are so small that it do infect the bacteria’s too and its during that time; we call it Bacteriophage; often shortage to phage. Many microbiologist through out the world; consider the viruses as non-living entities; as they donot generally accepted definition of LIFE. They lack self-reproduction outside a host cell, bu unlike parasites, viruses are generally not considered to be true living organisms.
Viruses are made of proteins; One such protein is HEMAGGLUTININ and the other is NEURAMINIDASE. H5 stands for the fifth of several known types of the protein Hemagglutinin. N1 stands for the first of several known types of the protein Neuraminidase. ‘A’ stands for the species of Infuenza (A,B or C). Together they make the term H5N1 strain. Asian lineage HPAI A(H5N1) is divided into antigenic clades. “Clade 1” includes human and bird isolates from Vietnam, Thailand and Cambodia and bird isolates from Laos and Malaysia. “Clade 2” viruses were first identified in bird isolates from China, Indonesia, Japan and South Korea before spreading wetsward to the Middle East, Europe and Africa. The “Clade 2” viruses have been primarily responsible for the hman H5N1 infections that have occurred during late 2005 and 2006, according to WHO. Genetic analysis has identified six subclades of clade 2, three of which have a distinct geographic distribution and have been implicated in human infections.
The distribution map is given below:
1. Subclade 1, Indonesia
2. Subclade 2, Middle East, Europe and Africa
3. Subclade 3, China
Now lets discuss about the term HPAI A(H5N1); Just like other Bird Flu viruses; H5N1 strains are called “highly pathogenic” (HP) and “low-pathogenic” (LP). Avian Influenza viruses that cause HPAI are highly virulent and mortality rates in infected flocks often approach 100%. LPAI viruses have negligible virulence, but these viruses can serve as progenitors to HPAI. The current strain of H5N1 responsible for the deaths of birds across the world is an HPAI strain; all other current strains of H5N1, including a North America strain that causes no diseases at all in any species, are LAPI strain. All HPAI strains identified to date have involved H5 and H7 subtypes. In general a highly pathogenic avian virus is not highly pathogenic to either humans or non-poultry birds.
Influenza A viruses are significant for their potential for diseases and deaths in humans and other animals. H5N1 is easily transmissible between birds facilitating a potential. While H5N1 undergoes specific mutations and reassorting creating variations which can infect species not previously known to carry the virus, not all of these variant forms can infect humans. H5N1 as an avain virus preferentially binds to a type of galactose receptors that populate the avain respiratory tract from the nose to the lungs and are virtually absent in humans, occuring only in and around the alveoli, structures deep in the lungs where oxygen is passed to the blood. As a result of which the virus can not be expelled by coughing and sneezng, the usual route of transmission. H5N1 is mainly spread by domestic and poultry, but through the movements of infected birds and poultry products and through the use of infected poultry manures as fertilizer or feed. Humans with H5N1 have typiclly caught it from chickens, which were in turn infected by other poultry or waterfowl. Migrating waterfowl, geese and sawns etc carry H5N1, often without becoming sick. Many species of birds and mammals can be infected with HPAI A (H5N1), but the role of animal;s other than poltry and waterfowl as disease – spreading hosts is unknown.
H5N1 strain has the ability to mutate and the mutated form becomes; extremely dangerous. Each specific known genetic variation is traceable to a virus isolate of a specific case of infection. THROUGH ANTIGENIC DRIFT, H5N1 has mutated into dozens of highly pathogenic varieties divided into genetic clades which are known from specific isolates, but all currently belonging to genotype Z of avian influenza virus H5N1, now the dominant genotype.
Infected birds transmit H5N1 through their saliva, nasal secretions, faeces and blood. Other animals may become infected with the virus through direct contact with these bodily fluids or through contact with surfaces contanminated with them. H5N1 remain infectitious after over 30 days at 0 degree centigrade (32 Fahrenheit; over one month at freezing temperature) or 6 days at 37 degree (98 Fahrenheit; one week at human body temperature) so at ordinary temperatures it lasts in the environment for weeks.
It was in October 2004, researchers discovered that H5N1 is far more dangerous than was previously believed. WaterFowl were revealed to be directly spreading the highly pathogenic strain of H5N1 to chickens, crows, pigeons and other birds and the virus was increasing its ability to infect mamamals as well.
In general, humans who catch a humanized Infuenza A Virus (a human flu virus of type A) usually have symptoms that include Fever, Cough, Sore throat, muscle aches, conjunctivities and in severe cases, severe breathing problems and pneumonia that may be fatal. The severity of the infection depends to a large part on the state of the infected person and whether the particular starin has been exposed to the strain before.
Researches are on the way to make a effective vaccines for stopping this “BIOLOGICAL DISASTER” Hope it is made soon and we can stop another person getting affected by it; and lets join hands to make a better, safer, stonger and a disaster free world for all of us.
Mr. Mainak Majumdar
Disaster Management Specialist and Consultant