I. Introduction:
1. Bird Flu:
Infectious disease of birds caused by type A (H5N1) strains of influenza virus. Bird flu is also referred to as avian (bird) influenza (flu). The H5N1 virus spreads rapidly among birds destroying their internal organs and has a mortality that could reach 100% within 48 hours.
2. Migratory Water Fowl the Carriers of the Disease:
Migratory water fowl carry the virus. These infected birds shed the virus through their droppings, saliva and nasal secretions. Domestic poultry become infected from contact through contaminated water, feed, and soil or by inhaling the airborne virus..
3. Spread of the Disease to Humans:
A strain of the virus, the H5N1 is responsible for the current incidence of disease in humans. Found in the intestine of birds, the virus is excreted through faeces. It spreads through contaminated nasal, respiratory and faecal material from infected birds. The World Health Organisation has not found proof to suggest that the virus is transmitted through food..
4. Human Deaths due to the Disease:
Since the outbreak of bird flu in 2003, the H5N1 virus has infected 388 people in 15 countries resulting in the death of 246 of them, according to the World Health Organisation (WHO)..
5. Fear of a Pandemic:
The avian influenza virus H5N1 could mutate and evolve into a form that is easily spread between people resulting in an influenza pandemic which could sweep across the globe in a matter of months, killing millions and causing economic and social havoc..
6. No Proof of Human-to-Human Transmission:
No human-to-human transmission has been confirmed in the current outbreak..
7. Symptoms in Humans:
Typical influenza-like symptoms such as fever, cough, sore throat and muscle aches. Other symptoms include, eye infection, acute respiratory distress, viral pneumonia, and kidney failure..
8. Treatment:
Antiviral drugs are effective against influenza A virus strains but have some limitations. Two drugs oseltamivir (commercially called Tamiflu) and zanamivir (commercially called Relenza) are effective in treating seasonal influenza. The drugs have to be administered early. Tamiflu is costly and in limited supply and fears have been expressed that the virus may develop resistance to it..
9. First Pre-Pandemic Vaccine Against Bird Flu:
In May 2008 the European Commission granted licence to market the world’s first pre-pandemic vaccine against bird flu, intended to be used in the first stages of a bird flu pandemic. Developed by the British pharmaceutical firm GlaxoSmithKline, the Prepandrix vaccine targets the most virulent strain of the virus that can be fatal to humans. The vaccine is seen as a significant step to cope with the influenza pandemic.
10. Precautions to be Taken:
II. Background:
1. Influenza:
Influenza is the result of a viral infection of the respiratory tract. It spreads through tiny airborne droplets of respiratory fluids from an infected person. These droplets can be released into the air when such person coughs and sneezes.
2. Types of Influenza Virus:
Influenza viruses are divided into three types:
A, B and C. The type A influenza viruses which infect humans, birds and animals such as pig and horse are of particular concern as they are capable of swapping genes and creating new varieties of the virus. The new varieties are not detected and stopped by the immune system.
3. Mutations of the Influenza Virus:
Experts believe that mutations commonly occur in the influenza virus and could produce a highly infectious form of new strain. Once such a strain appears, a flu pandemic can easily occur as people would have no immunity to the H5 type of haemagglutinin.
4. A H5N1 Strain:
After closely examining the cases of influenza from the new H5N1 strain, health experts believe that multiple infections of the new strain might have occurred and that both the source and mode of transmission are still uncertain.
5. History Flu Pandemic:
Most lethal influenza pandemic ever, killed 20 million people; caused by H1N1 subtype virus.
Started in China and resulted in the death of more than 750,000 people worldwide; caused by H2N2 virus.
In 1968 Hong Kong flu pandemic (world-wide epidemic) killed 700,000 people world-wide; caused by H3N2 virus.
The “bird flu” in Hong Kong represents the first documented human infections with the avian influenza A(H5N1) virus. The virus infected 18 people killing
6. In order to curb the spread of the disease, the authorities in Hong Kong slaughtered the region’s 1.2 million chicken in December 1997.
H5N1 virus strain affects humans in Asia, Europe and other parts of the globe. The WHO warned that the virus could mutate and kill up to 150 million people.
III. Current Global Concern Over the Spread of Bird Flu:
1. Global Spread of the Disease - More than 65 Countries Affected:
Since the outbreak of the disease in December 2003 in East Asia, it has spread globally. More than 65 countries across Asia, Europe, Africa, and the Middle East have been affected by bird flu. The spread across continents is attributed to migratory birds, movement of live birds and poultry products.
2. Human cases have been reported from 14 countries of which seven are in Asia.
3. Millions of Chicken Killed Across Asia:
Following the outbreak of bird flu in December 2003 tens of millions of chicken and ducks across Asia had been killed to prevent the avian influenza virus spreading to humans.
4. Recent Outbreaks in Many Asian Countries - Concern over the Risk of Igniting an Influenza Pandemic:
Outbreaks of bird flu have been reported in recent months from a number countries in Asia including China, India, Indonesia, Myanmar, Thailand and Vietnam. There is growing concern that that the H5N1 virus could mutate by mixing with other seasonal influenza strains which could ignite an influenza pandemic.
5. WHO Feels that the Bird Flu is the Most Serious Global Health Threat:
The World Health Organisation (WHO) has warned about the risk to the global community from the bird flu. It has observed that avian influenza is the most serious health threat facing the global community.
6. H5N1 Virus has Become More Lethal:
Scientists point out that the H5N1 virus has become more lethal with time. In May 2005, over a thousand migratory water-birds were killed by the H5N1 virus in China. The virus has gained the ability to infect more species, including cats and tigers.
7 Genetic Evidence of Evolution of the H5N1 Virus:
Reports from China suggest that pigs in China were found to be carrying H5N1 virus. There were similar reports from Indonesia. Avian and human flu viruses can both infect pigs and exchange genes. Thus, pigs could act as mixing vessels that produce flu strains dangerous to humans. This suggests that the H5N1 virus has become more infectious to humans. There is also genetic evidence to prove the evolution of the H5N1 virus.
8 Equitable Access to Bird Flu Vaccines:
In June 2007, member-states of the WHO agreed to address the question of putting in place an equitable arrangement for sharing bird flu samples and benefits of research. Indonesia which bore the brunt of bird flu outbreaks, had stopped sending samples to the WHO in protest against the absence of any guarantee of access, in the event of a pandemic outbreak, to vaccines that might be developed using its samples.
9. Prevention of Pandemic - Containing the Virus at Source:
Experts point out that the best method of preventing a pandemic is containing the virus at source which is the animal sector. Among the important control measures are practising bio-security, culling of poultry along with adequate compensation to farmers, and vaccination of poultry.
IV. Threat of Bird Flu in India:
1. Background:
The Avian influenza or bird flu disease is under control in India after the outbreak of the disease in Maharashtra and Gujarat in February 2006, according to officials of the Animal Husbandry Department.
A regular countrywide surveillance mechanism is on to check any possible outbreak of the disease in future. Samples were regularly being drawn on a countrywide scale and were being tested for H5N1 virus. Since the initial outbreak in February 2006, only 50 samples out of 2,00,000 samples had tested positive, according to officials. Zoning surveillance mechanism as part of a long-term strategy is also being considered by the Centre.
After the outbreak of bird flu in India about 10 lakh birds had been culled. Poultry farmers got compensation on a 50:50 basis from both the Central and State Governments.
The loss to the domestic poultry industry after the outbreak of bird flu in India is estimated to be Rs. 22,000 crore.
According to the High Security Animal Disease Laboratory (HSADL) the bird flu virus in India came through migratory birds from China which carried the virus via Europe and West Asia.
In July 2007 an outbreak of the highly pathogenic H5 avian influenza was noticed in a village near Imphal in Manipur after samples of affected birds tested positive on July 25, 2007, at the High Security Animal Disease Laboratory in Bhopal and the National Institute of Virology in Pune. Over 132 infected birds of a total flock of 144 from a single poultry unit died in six days from July 7, 2007.
About 1.5 lakh birds within a 5-km radius of the affected village would be culled in the next ten days from July 26, 2007. The Rapid Response Teams (RRTs), comprising of animal husbandry and community health personnel, started the operations. The Government would compensate the farmers for the destruction of the birds.
No case of human infection had been reported. The 21 family members in a cluster of three houses handling poultry and nine veterinary staff, who got exposed to the infected birds, were provided prophylactic cover and were reported to be healthy.
In mid-January 2008 cases of bird flu outbreak were reported from some districts in West Bengal. The disease soon spread to 13 of the 19 districts of West Bengal. About 29 lakh birds were culled in the 13 districts till February 2008.
2. November-December 2008 - Outbreak of Bird Flu in North-East and West Bengal:
In the last week of November 2008 outbreak of bird flu was reported from Assam and in December 2008 parts of Meghalaya and West Bengal were also affected by the disease.
3. Bird Flu Under Control in India:
On December 19, 2008, the Department of Animal Husbandry said that there was no further report of unusual mortality of poultry in any part of the country. The High Security Animal Disease Laboratory in Bhopal did not report of any poultry sample testing positive for bird flu in any part of the country, including Assam and West Bengal.
V. Conclusion:
1. Suggested Measures to Combat the Spread of the Avian Influenza:
The following measures have been suggested by officials in Europe to combat the spread of the Avian Influenza:
A. Reducing the Chances of Human Infection:
Controlling the spread of the disease in poultry through culling and changes in the farming system. Increase in collaboration between the animal and public health sectors. Strengthening communication to rural areas and improving the environmental detection of the virus.
B. Strengthening the Early Warning System:
C. Containing the Spread at the Source:
Establishing an international stockpile of antiviral drugs and developing mass delivery systems.
D. Reducing Deaths and Social Disruption:
2. Bio-Security Measures:
Under the proposed bio-security measures steps are to be taken to break the link between the migratory birds and domestic water fowl (ducks and chicken). This is done through "netting" i.e. separating migratory birds, their implements and feed from domestic water fowl. About 20 million migratory birds arrive in India between February and March and June-July from North and Northwest countries.
3. WHO Advised Countries to put in Place National Preparedness Plans to Contain the Spread of Avian Influenza:
The World Health Organisation (WHO) urged all countries to put in place national preparedness plans to prevent avian influenza and to contain its spread.
Sakshi Education
Published date : 10 Aug 2009 01:57PM
