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1-3-5-7-9 (H7N9 map 地圖)

(updated on 2014/01/09)

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In Hong Kong, the first case of H7N9 was reported in an Indonesian domestic helper who visited Shenzhen in Guangdong in the last week of November 2013. What is H7N9? Influenza A virus exists in various forms, as differentiated by the specificities of their H and N antigens on the virus surface. These are denoted by numbers 1, 2, 3, 4…. Influenza A circulates widely amongst birds, for which the name "avian influenza" is derived. Avian influenza is classified into 2 categories by their propensity for severe disease in the host - low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (LPAI). H5N1 has long been known as a cause of HPAI, which has led to deaths in poultry, and occasionally in human.

On 31 March 2013, the Chinese Government reported the first human cases of influenza A H7N9, an avian influenza virus. Most cases could be dated back to the first half of the year 2013, as illustrated in the map. A significant proportion of the reported cases developed severe diseases and some had died, a pattern not unlike that for H5N1. While H7N9 has not been previously reported in human, the H7 family has long been known to be associated with LPAI. Human infections with H7 (not H7N9) have been reported: In the Netherlands there was a cluster of 89 H7N7 cases in 2003, while sporadic cases have been reported in UK, Canada and USA over the years. There were scientific studies suggesting that H7N9 has originated from a reassortment of 3 virus strains that have infected birds. Generally speaking, the Influenza A family is a much more common cause of seasonal influenza than avian influenza in human population. In the winter season in 2012-2013, both H3 and H1N1(2009) were circulating in USA, while H1N1(2009) was the main influenza A virus detected in Hong Kong. For now, H7N9 is a new addition to our influenza world. Data for the H7N9 map were extracted from media reports.

香港首宗人類感染H7N9呈報病例發生在一名印藉家庭傭工身上，她2013年11月底曾經到過深圳。H7N9是什麼？它是甲型流感病毒多種亞型之一，病毒以表面的H和N特徵蛋白的號碼1, 2, 3, 4…命名。甲型流感病毒在禽鳥之間傳播，故此又稱『禽流感』。禽流感病毒一般分兩大類：高致病型和低致病型。H5N1是高致病禽流感病毒的一個例子，令家禽因病而死，偶爾感染人類並且引發嚴重疾病。

2013年3月31日，中國政府宣佈首次發現人類甲型H7N9流感，屬新禽流感個案，最早發病的追溯至同年2月中。地圖顯示確診者分佈華東一帶，不少人患重病甚至死亡，情況和過往的H5N1人類感染禽流感相似。雖然H7N9以前從未發生在人類身上，H7組別是已知的低致病型禽流感病毒。2003年，荷蘭發生89例人類H7N7感染群集，而英國、美國和加拿大等地方曾出現人類H7零星個案。最新科研結果顯示，H7N9可能源自三種不同的禽流感病毒基因重組。整體而言，甲型流感病毒引起的季節性流感比人類禽流感更為普遍。剛過去的冬季（2012-2013），H3和H1N1(2009) 都在美國廣泛傳播，而H1N1(2009) 則是香港的主流病毒。H7N9為流感病毒世界帶來又一新成員。地圖資料取材自不同的媒體報導。

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。