世界卫生组织（WHO）28日做好准备，拟将猪流感大流行警戒等级由第四级升高为第五级。这显示病毒极有可能已在人与人之间广泛传播。同时，世卫公布的对6个不同“流感大流行级数”的定义如下：
第一级：病毒在动物间传染，但没有传出人类感染病例。
第二级：已知一种动物流感病毒在人类造成感染，因此被视为潜在大流行威胁。
第三级：有动物流感病毒或动物与人类流感重组病毒造成零星或小规模的人类传染，但这种人与人之间传染还不足以造成社区感染。
第四级：动物流感病毒或动物与人类流感重组病毒造成的人与人间传染，足以造成社区传染。大流行风险骤升。本级重点在于控制病毒蔓延。
第五级：人与人之间传染在同一地区蔓延到至少两国。强烈显示即将发生大流行。
第六级：大流行级。人与人之间病毒传染，在同一地理区至少在两国传播，并扩散到同一区的另一个国家。
猪流感疫情：世卫警告全球作最坏准备
世卫组织发言人4月29日说，猪流感发展不可预测，大流感可以由轻微爆发开始，造成大量死亡，所有国家应作最坏准备。截止4月28日为止，至少有19个国家出现确定或疑似病例，世卫拟调高警戒至第五级。
法新社报导，世卫助理总干事福田敬二说，目前的猪流感疫情会如何发展仍是不可预测，但必须提出警告，在1918年西班牙的大流感疫情，也是由轻微爆发开始，结果造成数以千万人死亡。他提醒各国要作好最坏打算，特别是发展中国家。福田敬二又说，现阶段来说，流感大流行不是不能避免，但也不可以掉以轻心。
4月28日晚，世卫发言人哈特尔说，如果美国证实猪流感病毒已在人与人之间广泛传播，这也就是该病毒已经在两个国家的人群中传染，那么世卫就会进一步将全球流感疫情警戒等级提高到第五级。
世界卫生组织28日说，从墨西哥回来的猪流感病患，可能已经将这一病毒传给其他美国人。在美国，有一些学校停课，好些人开始戴上口罩，不过，大体而言，美国人的生活没有多大改变。欧洲医疗专家也担心，同猪流感病患接触的一些欧洲人可能已经受感染，这些人可能在未来几天显现出猪流感的症状来。
根据世卫定义，第四级的情况是：动物流感病毒或动物与人类流感重组病毒造成的人与人间传染，足以造成社区传染。28日晚些时候，世卫发言人哈特尔在日内瓦记者会上说，如果美国证实猪流感病毒已在人与人之间广泛传播，这也就是该病毒已经在两个国家的人群中传染，那么世卫就会进一步将全球流感疫情警戒等级提高到第五级。
在这同时，俄罗斯科学院病毒学院院长利沃夫和香港大学微生物学系系主任袁国勇异口同声的警告，这次的猪流感疫情演变成全球大疫情的可能性非常高。利沃夫说，这股疫情可能在一个星期内袭击俄罗斯。
Outbreaks and pandemics: a timeline
See how swine flu compares
TAGS: AVIAN FLU, BIRD FLU, BLACK DEATH, BUBONIC PLAGUE — ‘THE BLACK DEATH’, HONG KONG INFLUENZA, RUSSIAN FLU PANDEMIC, SARS, SWINE FLU, THE SPANISH FLU PANDEMIC
Swine flu, which has killed about 150 and sickened another 1,900 in Mexico since April 13, is spreading fast. Cases have now been confirmed in the U.S., Canada, New Zealand, Scotland and Spain, prompting governments to issue travel warnings and to declare public health emergencies. The swine flu has also stoked plenty of fear among the general public. For a little perspective, here’s a brief history of global outbreaks and pandemics:
Severe Acute Respiratory Syndrome (SARS)2002-2003
Death toll: Almost 800
Symptoms: High fever, headache and an overall feeling of discomfort. Some sufferers develop mild respiratory symptoms and a dry cough. About 10 to 20 per cent experience diarrhea. Most develop pneumonia.
How it spread: When a person touched a contaminated surface and then touched his or her mouth, nose, or eyes. Or person-to-person contact (coughing, sneezing). Chinese health officials in Guangdong province initially listed the first case of SARS as “atypical pneumonia.” It only went public when Dr. Carlo Urbani, who was working in Vietnam, reported it to the WHO (Urbani later died of SARS). Starting in early 2003, the virus spread to more than 30 countries, infecting 8,000 people, in a few months.
Avian flu (1997- )
Death toll: 257
Symptoms: Typical flu-like symptoms (fever, cough, sore throat, and muscle aches).
How it spread: Most commonly passed along through contact with infected poultry, or surfaces contaminated with secretion/excretions from infected birds. Person-to-person transmission is very rare. The first major outbreak occured in Hong Kong in 1997, with 18 cases (six died). The most recent outbreak began in December 2003. Avian flu has killed more than 60 per cent of those who have contracted the virus.
Hong Kong influenza (1968-1969)
Death toll: About one million
Symptoms: It’s often confused with the common cold. But the symptoms (high fever, joint pain, lack of energy) worsen and last longer. Symptoms normally cause a victim to become bedridden for up to two weeks.
How it spread: Human to human (coughing, sneezing). Named after the city where it was first detected in 1968, the virus returned in 1970 and 1972. The elderly were hardest hit. In the U.S., 34,000 fell victim to the Hong Kong influenza between September 1968 and March 1969.
The Asian flu pandemic (1957-1958)
Death toll: About four million
Symptoms: Fatigue, aches and pains and fever that can last two weeks.
How it spread: From person-to-person contact. The pandemic was first identified in the Far East in February 1957, and was detected in wild ducks in Southern China before mutating with the existing human flu strain. The virus first made its way to the U.S. in the summer of 1957 (in all, it would be blamed for 70,000 deaths in the U.S.). Although infection rates were highest among children and pregnant women, the elderly suffered the highest rates of death.
The Spanish flu pandemic (1918)
Death toll: 20 to 100 million
Symptoms: The flu was initially misdiagnosed as cholera, dengue or typhoid since (unlike other flu strains) victims experienced hemorrhaging from the nose, stomach, and intestine, or bled from the ears. Most deaths were caused by bacterial pneumonia caused by the influenza.
How it spread: Some researchers say it began in Tibet but moved towards Europe along trade/shipping routes. It was deadliest in young adults between 25 and 30, killing more men than women. By some estimates, as much as 40 per cent of the world’s population became ill.
Russian flu pandemic (1889)
Death toll: 1 million
Symptoms: Fever, pneumonia and traditional flu-like symptoms.
How it spread: The ‘Russian flu’ is believed to have originated in China, but spread rapidly throughout Europe before landing in North America, Japan and Latin America.
Bubonic plague —‘The black death’ (14th to 17th century)
Death toll: 25 million — the disease originated in Asia but some say it killed 50 per cent of Europe’s population, having spread by fleas.
Symptoms: Vomiting, diarrhea, respiratory failure, headache and swollen lymph glands. Other symptoms included spots on the skin that are red and then turn black, heavy breathing, vomiting blood, and pain caused by the decaying of the skin.
How it spread: Bites from infected fleas, rodents, and lice. There are still between 1,000 to 3,000 cases reported annually, but antibiotics can be used to treat the disease if caught early.
人类大流感回顾
随着猪流感疫情的进一步蔓延，世界卫生组织已经将猪流感的警戒级别调高至第四级，该组织总干事陈冯富珍表示，猪流感病毒有在全球广泛爆发的可能性。专家指出，当一种新型的病毒广泛传播，而大多数人还不具备抵抗这种新病毒的自然免疫力时，全球性的瘟疫就会爆发。至少从16世纪起，各种流感瘟疫就一直在以不规律的间歇不断爆发。
世界卫生组织宣布，北美爆发的猪流感疫情构成了国际关注的突发公共卫生事件，并将目前人类大流感警戒级别从第三级调高到第四级，即出现病毒在人与人之间持续传播的阶段。人类大流感警戒级别共分为六级，世界卫生组织表示，把警戒级别调高到第四级意味着出现人类大流感的可能性增加了，但并不是不可避免。
在过去的一个世纪里，全球性的流感瘟疫，也就是世界卫生组织所说的人类大流感，一共出现过至少五次。1918年至1919年爆发了被称为“史上最恐怖的流感”–西班牙流感，这种病毒也是H1N1型病毒的一个种类，主要袭击青壮年，当时造成了全球大约20%到40%的人口感染，死亡人数至少有4千万到5千万，是一战死亡人数的差不多五倍。这种病毒最早是在美国发现的，但是之所以得名“西班牙病毒”，是因为当时的西班牙媒体对这种瘟疫投入了大量的精力报道，而在第一次世界大战期间，许多其它国家的媒体处于严密的监控之下，无法进行自由报道。
20世纪的第二次大型全球性流感，是1957年爆发的所谓亚洲流感。这种流感病毒属于H2N2型病毒，最早在中国发现。该流感病毒早期感染的是儿童，后来则主要袭击老年人。这一波亚洲流感造成全球大约2百万人死亡。
1968年爆发的香港流感是上世纪疫情最轻的一次人类大流感。这种H3N2型流感病毒最早出现于香港，之后在接下来的两年中扩散到全世界。患病者主要是老年人，全球死亡人数大约为一百万。
进入21世纪之后短短的不到十年里，世界上已经出现了数次流感瘟疫，但是它们的严重性和死亡人数已经比20世纪时大大降低。2002年11月，在中国广东省出现了首例非典型性肺炎感染者。这种高危险性的肺炎简称萨斯，由于在2003年上半年在中国大部分地区以极快的速度广泛传播，加上中国有关卫生部门和政府机构在疫情出现的初期采取隐瞒的做法，导致了许多人的恐慌。据统计，全世界一共有8000人左右感染萨斯病毒，死亡人数约为800人，其中中国有将近 350人。
2003年，H5N1型高致病性禽流感病毒由越南蔓延到东南亚其它国家，中国也受到了一定程度的波及。禽流感病毒至今一共造成250多人死亡。与这次在墨西哥爆发的猪流感不同，禽流感病毒只能通过禽类向人类传播，而不会在人与人之间直接传播。
几乎年年都有不同程度的流感疫情出现。正是因为流感病毒变异的速度十分迅猛，所以也对医学界研制治疗药物和疫苗提出了很大的挑战。据世界卫生组织公布，全球每年都有300万到500万人感染严重的流感，其中大约有25万到50万人因流感而死亡。（德国之声）
