Lurking danger of a pandemic flu
The term, influenza, from the Italian word meaning "influence," was coined in 1357. Popular belief, at that time, blamed the development of flu on the influence of the stars. Influenza is commonly a respiratory tract disease whose severity varies from milder to lethal form depending on nature of the organism with its mutation capacity and susceptibility of the host influenced by immunity status.
All influenza viruses are divided into three types -- A, B or C -- depending on the virus' structure. Type A is responsible for lethal influenza pandemics, whereas type B causes smaller, localised outbreaks. Less common and more stable than other strains, type C has milder symptoms.
Nevertheless, type A influenza infects both human and animals, including birds, pigs, horses, whales and seals. Numerous influenza A sub-types exist, and they can combine to form even more sub-types. At least 15 flu subtypes affect birds, the most virulent of which is H5N1.
"Human influenza virus" usually refers to those subtypes that spread widely among humans. There are only three known A sub-types of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among humans. In the current epidemic, two influenza sub-types have proved especially dangerous -- H7N7, which sickened poultry workers in the Netherlands, and H5N1, which has been responsible for the majority of human and avian deaths in Asia.
Domestic poultry is very susceptible to H5N1 and can spread to people. Most people who had the virus worked directly with poultry, or had close contact with birds. Scientists are increasingly convinced that at least some migratory waterfowl are now carrying the H5N1 virus in its highly pathogenic form, sometimes over long distances, and introducing the virus to poultry flocks in areas that lie along their migratory routes.
Influenza A viruses undergoes constant stepwise changes in their genetic make-up. This strategy, known as antigenic drift, works well as a short-term survival tactic for the virus: the speed with which slight variations develop keeps populations susceptible to infection.
Pandemics occur when an entirely new subtype of influenza A virus emerges (antigenic shift) through recombination of human and animal antigens (swine or avian) for which people have little or no immunity, and for which there is no vaccine.
Flu pandemics in history
In 412 BC, Hippocrates, the father of medicine described a flu-like disease for the first time at Perinthus in North Greece. Diodorus Siculus recorded an epidemic that swept through the Athenian army in Sicily. Some historians have speculated that influenza may have contributed to the demise of Athens in 404 BC. In 1485, the "sweating sickness," a flu-like malady, sickened hundreds of thousands of people in Britain. The Lord Mayor of London, his successor, and six aldermen died. The first recorded global spread of flu swept across Asia in 1580, then infected Africa, Europe, and ultimately America, where over 90 per cent of the populace was afflicted. During the 18th century, at least three pandemics occurred (1729-1730, 1732-1733, and 1781-1782). The 1781 pandemic was a major outbreak that spread across Russia from Asia. Four major influenza epidemics were recorded between 1830 and 1848. The 1830-1831 epidemic may have originated in China; and in 1833 influenza advanced westward out of Russia into Europe. In 1836-1837, influenza diffusion was largely north to south, and in 1847-1848 the disease swept through the Mediterranean to southern France and then elsewhere in Western Europe. The Spanish Flu of 1918 is considered the most severe of all influenza outbreaks to date, which killed more people than World War I, at somewhere between 20 and 40 million people. More people died of influenza in a single year than in four-years of the Black Death (bubonic plague) from 1347 to 1351. Known as "Spanish Flu" or "La Grippe" the influenza of 1918-1919 was a global disaster. In February 1957, the Asian influenza pandemic was first identified in the Far East, which was a much milder illness; the global death toll was estimated to be around 2 million. The most recent influenza pandemic occurred in 1968 with the Hong Kong Flu (H3N2) outbreak, caused around 1 million deaths worldwide. Countries affected
The most recent epidemics are thought to have arisen in China. To date, the countries with reported outbreaks are Korea, Vietnam, Japan, Thailand, Cambodia, Laos, Indonesia, China, and Malaysia. In late July 2005, the virus spread geographically beyond Asia to affect poultry and wild birds in the Russian Federation and adjacent parts of Kazakhstan and Mongolia. In October 2005, the virus was reported in Turkey, Romania, Croatia, Ghana, Togo, Czech Republic, Germany, and Ukraine. The first officially announced bird flu outbreak in Bangladesh occurred in February 2007 and spread to 11 out of its 64 districts. A fresh outbreak of bird flu cropped up in Bangladesh since January 2008 affecting 48 upazilas in 29 districts and six metropolitan areas, having estimated 325,000 infected birds in 93 poultry farms with renewed fear of a possible spread. There are reports that hundreds of crows and other birds along with poultry were dying every day across the country due to bird flu. Because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus one day could be able to infect humans and spread easily from one person to another. If H5N1 virus were to gain the capacity to spread easily from person to person, an influenza pandemic could begin. WHO has made a conservative estimate from 2 million to 7.4 million deaths if it takes a pandemic turn. For many countries, it would also bring economic challenges because of the costly preventative measures and the loss of business. Currently, the poultry industry has sustained an estimated $10 billion in losses globally. More than 140 million birds were affected, either by having the virus or through culling as a preventative measure to contain the disease. In a worst case scenario involving future outbreaks, experts predict that a global influenza could drop the global GDP by 2%, which would mean a loss of about $800 billion a year. In order to be able to stop the virus in its tracks and limit the spread of infection to a small area once an outbreak is reported, quick and effective intervention is the key. A mixture of vaccination, quarantine measures, bird culling, antiviral drugs, door-to-door surveillance, cleanliness of poultry farms and clean handling, cooking of chicken at appropriate temperature, using masks and gloves, ban on susceptible poultry import are the measures to ensure that infection is confined to a small area once an outbreak is reported. However, the flu will still go out of control if measures are taken to stop the flu only after the virus has already spread to a large area. Thus, nothing is more important than effective communication between poultry farmers and scientists to quickly intervene upon any signs of flu infection. There is little point in having so many methods of prevention, if no one knew about them. People must know the basic hows, whats and whys about avian flu, and most importantly, how they can prevent the risk of ever contracting it for greater public safety.
In 412 BC, Hippocrates, the father of medicine described a flu-like disease for the first time at Perinthus in North Greece. Diodorus Siculus recorded an epidemic that swept through the Athenian army in Sicily. Some historians have speculated that influenza may have contributed to the demise of Athens in 404 BC. In 1485, the "sweating sickness," a flu-like malady, sickened hundreds of thousands of people in Britain. The Lord Mayor of London, his successor, and six aldermen died. The first recorded global spread of flu swept across Asia in 1580, then infected Africa, Europe, and ultimately America, where over 90 per cent of the populace was afflicted. During the 18th century, at least three pandemics occurred (1729-1730, 1732-1733, and 1781-1782). The 1781 pandemic was a major outbreak that spread across Russia from Asia. Four major influenza epidemics were recorded between 1830 and 1848. The 1830-1831 epidemic may have originated in China; and in 1833 influenza advanced westward out of Russia into Europe. In 1836-1837, influenza diffusion was largely north to south, and in 1847-1848 the disease swept through the Mediterranean to southern France and then elsewhere in Western Europe. The Spanish Flu of 1918 is considered the most severe of all influenza outbreaks to date, which killed more people than World War I, at somewhere between 20 and 40 million people. More people died of influenza in a single year than in four-years of the Black Death (bubonic plague) from 1347 to 1351. Known as "Spanish Flu" or "La Grippe" the influenza of 1918-1919 was a global disaster. In February 1957, the Asian influenza pandemic was first identified in the Far East, which was a much milder illness; the global death toll was estimated to be around 2 million. The most recent influenza pandemic occurred in 1968 with the Hong Kong Flu (H3N2) outbreak, caused around 1 million deaths worldwide. Countries affected
The most recent epidemics are thought to have arisen in China. To date, the countries with reported outbreaks are Korea, Vietnam, Japan, Thailand, Cambodia, Laos, Indonesia, China, and Malaysia. In late July 2005, the virus spread geographically beyond Asia to affect poultry and wild birds in the Russian Federation and adjacent parts of Kazakhstan and Mongolia. In October 2005, the virus was reported in Turkey, Romania, Croatia, Ghana, Togo, Czech Republic, Germany, and Ukraine. The first officially announced bird flu outbreak in Bangladesh occurred in February 2007 and spread to 11 out of its 64 districts. A fresh outbreak of bird flu cropped up in Bangladesh since January 2008 affecting 48 upazilas in 29 districts and six metropolitan areas, having estimated 325,000 infected birds in 93 poultry farms with renewed fear of a possible spread. There are reports that hundreds of crows and other birds along with poultry were dying every day across the country due to bird flu. Because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus one day could be able to infect humans and spread easily from one person to another. If H5N1 virus were to gain the capacity to spread easily from person to person, an influenza pandemic could begin. WHO has made a conservative estimate from 2 million to 7.4 million deaths if it takes a pandemic turn. For many countries, it would also bring economic challenges because of the costly preventative measures and the loss of business. Currently, the poultry industry has sustained an estimated $10 billion in losses globally. More than 140 million birds were affected, either by having the virus or through culling as a preventative measure to contain the disease. In a worst case scenario involving future outbreaks, experts predict that a global influenza could drop the global GDP by 2%, which would mean a loss of about $800 billion a year. In order to be able to stop the virus in its tracks and limit the spread of infection to a small area once an outbreak is reported, quick and effective intervention is the key. A mixture of vaccination, quarantine measures, bird culling, antiviral drugs, door-to-door surveillance, cleanliness of poultry farms and clean handling, cooking of chicken at appropriate temperature, using masks and gloves, ban on susceptible poultry import are the measures to ensure that infection is confined to a small area once an outbreak is reported. However, the flu will still go out of control if measures are taken to stop the flu only after the virus has already spread to a large area. Thus, nothing is more important than effective communication between poultry farmers and scientists to quickly intervene upon any signs of flu infection. There is little point in having so many methods of prevention, if no one knew about them. People must know the basic hows, whats and whys about avian flu, and most importantly, how they can prevent the risk of ever contracting it for greater public safety.
For all latest news, follow The Daily Star's Google News channel.
Comments