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Topic: 香港觀鳥會就最近禽流感蔓延的意見及建議(二) HKBWS's View 2 (Read 765 times) |
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香港觀鳥會就最近禽流感蔓延的意見及建議(二) HKBWS's View 2
« on: Nov 5th, 2005, 4:19pm » |
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香港觀鳥會就最近禽流感蔓延的意見及建議(二) 2005年10月25日
容易感染病毒的高危鳥種
1. 蒼鷺：H5N1病毒與蒼鷺的關聯較高，每年都有一千只蒼鷺在香港渡冬，大部份都在 米埔及后海灣出沒，在泰國，牠們是頗常見的冬候鳥。
雀鳥遷徙與禽流感病毒散播的關係
1. 分析雀鳥的遷徙路線，我們可以推斷東南亞的禽流感病毒其實可以擴散至全球，當 印尼的候鳥北遷至西伯利亞，便有可能把病毒傳給飛往歐洲的候鳥，這可能是歐洲 爆發禽流感的原因。基於此，我們甚至可以預期未來一至三年，禽流感將會在美國 出現。
2. 其實，以上分析並非新知，所有禽流感專家均瞭如指掌。
3. 社會亦不時傳出控制（減少）候鳥以遏止禽流感蔓延的說法，我們強調這是一個不 切實際的想法。首先，沒有人知道人為減少雀鳥所導致的生態失衡的真正後果，但 選擇性地消滅雀鳥肯定只會製造另一個更大的問題。第二，選擇性地消滅雀鳥並不 合乎成本效益，甚至根本不可行。假如我們不停地圍剿雀鳥，較弱的雀鳥將會更容 易受病毒感染。
感染禽流感病毒的機會
1. 根據禽流感病毒的測試，香港七千個樣本中，只有三個樣本發現病毒，而三個樣本 均是已死去的雀鳥（包括一只游隼、一只蒼鷺）
2. 即使雀鳥帶有病毒，但仍然沒有實質證據支持雀鳥會直接感染人，即使理論上有機 會，但機會也是極微，事實上有很多例子顯示，很多人即使接觸帶病毒的野鳥或飼 養雀鳥也沒有受感染。
3. 約一百宗禽流感個案中，有少量跡象顯示一至兩個個案是由雀鳥直接感染，大部份 都是由飼養的家禽所傳染。即使在高濃度病毒的家禽飼養場，並非所有接觸這些家 禽的人都受到感染，醫學界專家可以提供更具體的數據。
4. 病毒從雀鳥傳播到家禽的機會似乎更高。
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HKBWS information and comments on Avian Flu (2)25 October 2005
Bird species that are considered high risk on transmitting H5N1
1. Grey Heron: H5N1 has been more frequently associated with Heron species than other species. There were over 1000 Grey Herons in Hong Kong in Winter. Most of them are in the Mai Po – Deep Bay area. They are “fairly common winter visitor” in Thailand.
The effect of bird migration on the spread of Avian Flu
1. The implication from the migratory route analysis is that Avian Flu in SE Asia can be transmitted to all over the world. Migratory birds in Indonesia will move north to Siberia and pass the virus to birds that migrate through Europe. This explains the outbreak in Europe. Based on this concept, we should expect virus outbreak in America too, may be in 1-3 year’s time.
2. There is nothing new in the above analysis. The result is already known to all Avian Flu specialists.
3. From time to time, there are calls to stop Avian Flu by controlling (reducing) the migratory birds. We must say this is not realistic at all. First of all, we do not know the exact consequence of upsetting the balance of nature by eliminating the birds. By eliminating the birds indiscriminately, it is very likely a big problem will result from our action. Secondly, it is not cost effective or even possible to eliminate all birds. If one keeps on chasing the birds, we have to face the danger that birds that are less healthy may have greater change of being infected by the virus.
Some figures on probabilities of contracting Avian Flu
1. Based on Avian Flu tests on wild birds in Hong Kong, out of about 7000 samples, the number birds having the flu virus is about 3. In all cases, the virus was found in dead birds (1 dead Peregrine Falcon, 1 dead Grey Heron, and may be a third bird?)
2. Even when there are wild birds carrying the virus, the chance of human getting the virus directly from wild bird is virtually unknown. Even though this is theoretical possible, the chance is extremely low. There are many examples of human in direct contact with wild birds or captive birds carrying the virus but none seems to have contracted the disease.
3. Out of may be about 100 cases of Avian Flu, there are minor evidences that may be 1-2 cases due to direct contact with wild birds. Most of the cases are due to direct contact with poultry birds from farms. Even in situations that there are high concentration of H5N1 such as in poultry farm outbreaks, not everybody in contact with the virus will be infected. Medical experts may be able to supply more concrete figures on this.
4. The spread of virus from bird to poultry birds seems to be high.
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| « Last Edit: Nov 5th, 2005, 11:23pm by Webcreeper » |
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香港觀鳥會 經理(項目及傳訊)
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