Until recent outbreaks of highly pathogenic H5N1 strain of bird flu virus, many people thought the virus has gone away. But it has not really; it is still around. Experts say it was largely "dormant" in recent months. Now the virus returns with more strength and has become more widespread.
Ninety nine commercial and backyard poultry farms in 31 out of our 64 districts have reportedly been infected with the deadly virus so far and it continues to spread. Everyday new areas are found infected raising concern amongst government officials, farmers, scientists and the general people. Over 364000 chickens have been culled after detection of the virus in the country. Experts urged to take immediate steps to tackle the situation.
Last year, for the first time H5N1strain emerged as a threat. Experts urged to be prepared for an epidemic that could kill millions of the population and damage our poultry farms. But very few initiatives were taken since that time to prevent further outbreak and handle the emergency.
The virus is known to have infected nearly 335 people in 12 countries and killed 206 since 2003 worldwide, according to the World Health Organisation (WHO). Most of the human cases were linked with close contacts with sick birds. So far, no humans have tested positive in the country. But the people are at great risk as human cases of bird flu have generally been linked to the contact with infected poultry.
Bangladesh has 125,000 small and large poultry firms producing 250 million broilers and 6 billion eggs annually. About 4 million Bangladeshis are directly or indirectly associated with poultry farming.
Health experts fear that the H5N1 virus, if given enough opportunities, may develop the characteristics it needs to start another influenza pandemic. The virus has already met all prerequisites for the outbreak of a pandemic and gradually increases its ability to spread efficiently and sustainably among humans.
The virus can improve its transmissibility among humans through two principal mechanisms. The first is a “reassortment” event, in which genetic material is exchanged between human and avian viruses during co-infection of a human or pig. Reassortment could result in a fully transmissible pandemic virus, announced by a sudden surge of cases with explosive spread.
The second mechanism is a more gradual process of adaptive mutation, whereby the capability of the virus to bind to human cells increases during subsequent infections of humans. Adaptive mutation, expressed initially as small clusters of human cases with some evidence of human-to-human transmission, would probably give the world some time to take defensive action, if detected sufficiently early. The virus may mutate or change into a form that passes easily from human to human, causing an epidemic that could spread very rapidly in our densely populated country.
“In many places dead chickens are discarded in open air rather than culled or burred and faeces of the infected birds loaded with the H5N1 virus are not disposed of properly and dumped in public places. It poses a great threat for the spread of the virus along with the migratory routes of wild waterfowl. If this continues, the outbreaks will also continue,” warned Dr Vidyut Kumar, Convener of Bird Flu Control Room. “It is the backyard farms that pose a real danger more than the commercial ones. Proper awareness at individual level is very essential” he added.
Director of Instituted of Epidemiology, Disease control & Research (IEDCR), Mahmudur Rahman expressed that consumers should be aware of the risk of cross-contamination. When handling raw poultry or raw poultry products, persons involved in food preparation should wash their hands thoroughly and clean and disinfect surfaces in contact with the poultry products. Hand washing after handling any bird or sick chicken is very important and simply soap and hot water are sufficient for this purpose.
Consumers need to be sure that all parts of the poultry are fully cooked (no "pink" parts). Eggs also should be properly cooked (no "runny" yolks). The H5N1 virus is sensitive to heat. Normal temperatures used for cooking (700C in all parts of the food) will kill the virus.
Domestic ducks can now excrete large quantities of highly pathogenic virus without showing signs of illness, and are now acting as a "silent" reservoir of the virus, perpetuating transmission to other birds. This adds yet another layer of complexity to control efforts and removes the warning signal for humans to avoid risky behaviours.
In many places, poultry farms are placed over pond or lake and fish farming in same pond goes simultaneously. If these poultry are infected, it could spread the virus in the water by shedding the virus loaded faeces in underneath pond. It could devastate our entire bio-security, informed Mr Rahman.
However, fears of a new pandemic, which could claim millions of lives, have not been realised so far, even though the mortality rate of the disease among humans has risen above 60 percent.
Altogether, more than half of the laboratory-confirmed cases have been fatal. H5N1 avian influenza in humans is still a rare disease, but a severe one that must be closely watched and studied, particularly because of the potential of this virus to evolve in ways that could start a pandemic.