第2249期:Scientists Study Why Bird Flu Kills Some Animals, Not Others

Researchers are seeking to learn why bird flu kills some animals quickly but causes only moderate illness in others.
研究人员正在寻求了解为什么禽流感会迅速杀死某些动物，而对其他动物只造成轻度疾病。

In recent years, bird flu is believed to have killed millions of wild and domestic birds worldwide. Other animals such as seals, cats, dogs, and cows have also been infected.
近年来，据信禽流感已经在全球范围内杀死了数百万只野生和家禽。其他动物如海豹、猫、狗和牛也被感染。

The virus is officially known as H5N1. It has largely stayed out of the human population. However, the World Health Organization (WHO) reported that as of April 1, 2024, H5N1 had caused nearly 900 human infections and 463 deaths since 2003.
该病毒正式名称为H5N1。它主要未进入人类群体。然而，世界卫生组织（WHO）报告称，截至2024年4月1日，自2003年以来，H5N1已导致近900例人类感染和463例死亡。

Most of the human cases involved direct contact between people and infected birds. In cases of the virus spreading between humans, individuals involved were found to have had close and extended contact within households.
大多数人类病例涉及人与感染鸟类之间的直接接触。在病毒在人类之间传播的情况下，涉及的个人被发现曾在家庭内有密切和长期接触。

The currently spreading version of bird flu was first identified in 1959. But the illness did not start to cause concern among health officials until a bird flu outbreak hit Hong Kong in 1997. That outbreak caused severe sickness and deaths in some humans.
目前传播的禽流感版本于1959年首次被发现。但直到1997年禽流感在香港爆发，卫生官员才开始关注这种疾病。那次爆发导致一些人类出现严重疾病和死亡。

Scientists are still studying possible reasons the H5N1 virus has not heavily affected human populations. But some researchers fear the situation may change.
科学家们仍在研究H5N1病毒尚未对人类群体造成重大影响的可能原因。但一些研究人员担心这种情况可能会改变。

Like other viruses, H5N1 has mutated over time. During the last few years, one particular bird flu version has been spreading quickly and widely.
像其他病毒一样，H5N1随着时间的推移发生了变异。在过去的几年里，一种特定的禽流感版本迅速广泛传播。

Dr. Tom Frieden is a former director of the U.S. Centers for Disease Control and Prevention (CDC). He told The Associated Press about the ongoing outbreaks, “There's a lot we don't understand.”
Tom Frieden博士是美国疾病控制与预防中心（CDC）的前任主任。他在接受美联社采访时谈到持续的疫情时说：“还有很多我们不了解的情况。”

Frieden also heads the non-profit group Resolve to Save Lives. He added, “I think we have to get over the 'hope for the best and bury our head in the sand' approach."
Frieden还领导着非营利组织“决心拯救生命”。他补充说：“我认为我们必须克服‘希望最好并掩耳盗铃’的做法。”

Some researchers have theorized flu viruses that started in birds caused severe human pandemics. For example, pandemics that took place in 1918 and 1957 quickly spread among animals and people.
一些研究人员提出了理论，认为始于鸟类的流感病毒导致了严重的人类大流行。例如，1918年和1957年发生的大流行迅速在人类和动物之间传播。

Many experts think it would be unlikely the currently spreading virus will become a deadly, worldwide pandemic.
许多专家认为，目前传播的病毒不太可能成为致命的全球大流行。

But to prepare for that possibility, U.S. health officials are developing vaccines that might be needed. At this time, they are not planning other measures. This is because the virus is not causing severe disease in humans and there is no strong evidence it is spreading from person to person.
但为了应对这种可能性，美国卫生官员正在开发可能需要的疫苗。目前，他们没有计划采取其他措施。这是因为该病毒未在人类中引起严重疾病，并且没有强有力的证据表明它在人与人之间传播。

The U.S. Department of Agriculture has said U.S. animal outbreaks have been reported at numerous dairy cow farms and among more than 1,000 groups of poultry. At least four human infections have been reported among hundreds of thousands of people working at U.S. poultry and dairy farms.
美国农业部表示，美国的动物疫情已在众多奶牛场和1000多个家禽群体中报告。至少有四例人类感染报告涉及数十万在美国家禽和奶牛场工作的人员。

Worldwide, doctors have so far identified 15 human infections caused by the current version. That count includes one death, a 38-year-old woman in southern China in 2022. But officials said most of the identified people had either no signs of disease or only mild ones.
全球范围内，医生迄今已确认由当前版本引起的15例人类感染。这些病例中包括一例死亡病例，即2022年中国南方的一名38岁女性。但官员们表示，绝大多数被确认的感染者要么没有疾病迹象，要么只有轻微症状。

Some experts have wondered whether humans have built up some level of immunity after being infected by other virus forms or because of vaccination. But a study involving human blood samples suggested there was little to no existing immunity to this version of the bird flu virus.
一些专家怀疑人类是否在被其他病毒形式感染或因接种疫苗后建立了一定程度的免疫力。但一项涉及人类血液样本的研究表明，对这种禽流感病毒版本几乎没有现有的免疫力。