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H7N9 in Hong Kong 禽流感鬧香江

(updated on 2015/01/12)

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As of the end of December 2014, 11 human cases of avian influenza H7N9 have been reported in Hong Kong. All were imported cases from China, as the patients had history of travelling to Mainland China and some had possible exposure to poultry. The map shows the locations of the 11 cases in China and Hong Kong. Around the world the first human case was reported in China almost 2 full year ago, back in March 2013. The inset map shows the geographic distribution of all cumulative cases in China (as of 31 December 2014). The spatiotemporal relationship between H7N9 cases in Hong Kong and Guangdong is a cause for concern. This also suggests that the future occurrence of H7N9 in Hong Kong would depend largely on the control of outbreaks in poultry in Guangdong province. Data for the map were obtained from multiple media sources derived from reports in different health authorities.

截至2014年12月，香港報告了11例人類感染H7N9禽流感個案，全部曾經到過內地及部份可能接觸家禽，屬非本地感染。地圖顯示11名病者在香港和中國城鎮的大概位置。回顧H7N9歷史，全球首宗人類感染病例發生在兩年前的中國，現時累積總數四百多人。小圖顯示2014年12月31日全國的累積個案地理分佈。香港鄰近廣東，發生的11例H7N9在時間上也和廣東一樣，這點也是最令人擔憂。相信香港未來情況將會取決於廣東省的禽流感疫情的控制。地圖數據源自不同的媒體根據衛生部門發放資料所作的報導。

Avian influenza 禽流感

What is avian influenza? 什麼是禽流感?

Avian influenza (“bird flu”) is an infectious disease of birds caused by type A strains of the influenza virus. The infection can cause a wide spectrum of signs and symptoms in birds, ranging from mild illness, which may be passed unnoticed, to a rapidly fatal disease. Avian influenza has caused widespread epidemics in bird population in many parts of the world.
禽流感是一種由甲型流感病毒所引起的禽鳥傳染病。受感染的禽鳥可能呈現輕度癥狀，部份或會出現急性致命的疾病。禽流感已逐漸演變成在全球各地禽鳥中散播的疫症。

Is human susceptible? 人會感染禽流感嗎?

Avian influenza has remained a disease of the bird populations. So far there is no solid proof of efficient human to human transmission. A majority of the infected persons have a history of close contact with infected birds through, for example, slaughtering.
到目前為止，禽流感仍主要是禽鳥的疾病，並未有實證顯示病毒經人傳人快速擴散。在已知的人類感染禽流感個案當中，大部份曾經與受感染禽鳥有緊密接觸，例如屠宰等。

Vaccine? Prevention? 如何預防？

Currently effective vaccine against avian influenza is not available. Preventive measures include maintaining good personal hygiene, proper slaughtering procedures and handling of poultries, avoiding handling of wild birds. Suspected cases of infected birds should be promptly reported to the authorities.
現時還沒有有效的預防禽流感疫苗。預防措施主要包括保持個人衛生、採取適當屠宰程序及處理家禽程序和避免接觸野生雀鳥等。假使發現疑似感染H5N1或已死的雀鳥，應盡快告知有關當局。

Human influenza 人類流感

Influenza is a respiratory infection caused by the influenza virus, different forms of which are normally circulating in not just human beings but pigs and birds. All influenza viruses are divided into A, B and C, and further distinguished by their H and N antigens. There are currently 18 H (standing for haemagglutinin) and 11 N (standing for neuraminidase) antigens. Epidemics occurred when novel viruses are introduced to the human population. Pandemic influenza A (H1N1), previously referred as Swine flu, was an example causing worldwide outbreaks in 2009. The genetic structure of this influenza virus contains segments from pig, bird and human, reflecting the occurrence of reassortment. Studies suggested a case fatality rate of 0.4% for the novel infection, and a higher tendency for causing disease in young people compared to other forms of seasonal flu. Since 2009, the same virus has continued to cause outbreaks in different populations at different timepoints.

流感是指『流感病毒』引起的呼吸道傳染病，所影響的不單是人，也包括豬和禽鳥。『流感病毒』分甲、乙、丙三個主要類型，又以H（血凝素）和N（神經氨酸酶）基因作更仔細的分類，而現時已知的共有十八種H和十一種N基因。新類型流感病毒的出現，往往為人群帶來大爆發。二零零九年新發現的人類甲型H1N1流感病毒，初時被稱為豬流感。該病毒包含了人、豬和禽鳥的流感病毒基因，反映了基因重組現象。研究顯示，該流感的死亡率約百份之零點四。而相對於其他季節性流感，H1N1對年青人的致病機會相對較高。自2009年起，人類甲型H1N1流感病毒繼續在不同地點和時間在人群中爆發。

Preventive measures against avian influenza 禽流感防控措施

Hong Kong Government has implemented a number of preventive measures to reduce the risk of avian influenza outbreaks in the territory. For example, backyard poultry keeping is prohibited and local poultry farms are inspected on a regular basis. For chickens in local farms and imported chickens, vaccination is required and virological testing for H5 antigen is enhanced. At retail level, live poultry is not allowed to be kept overnight, and two 'rest days' per month have been introduced to all poultry stalls in public markets and fresh provision shops selling live poultry for thorough cleansing.

In addition, poultry workers and cullers are also invited to be vaccinated against seasonal influenza, so the chance of genetic reassortment between human and avian influenza viruses can be minimized.

香港政府已採取一連串的措施以減低香港爆發禽流感的風險，如禁止散養家禽及定期巡查本地家禽農場等。本地飼養場的雞隻及輸港雞隻均必須注射疫苗，並加強對其的病毒測試。至於零售層面，所有公眾街市的家禽檔位和售賣活家禽的新鮮糧食店不可把活家禽存留過夜，並須於每月兩次的休市清潔日中徹底清洗雞檔。

此外，政府亦有安排家禽從業員及禽鳥銷毀人員接種流感疫苗，從而減少人類流感病毒與禽流感病毒之間出現基因重組的機會。