美疾控中心通过检测血液样本中的抗体发现，美国超半数的人已经感染过新冠病毒，其中儿童感染率高达75%。研究人员发现，感染病毒人数在12月至2月期间也就是奥密克戎感染高峰期增加得最快。

 

More than half of Americans show signs of a previous Covid-19 infection, including three out of every four children, according to a new report released on Tuesday.

美国疾病控制和预防中心4月26日发布的一份新报告称，超半数美国人表现出曾感染新冠病毒的迹象，其中包括四分之三的美国儿童。

 

The findings from the Centers for Disease Control and Prevention (CDC) come after researchers examined blood samples from more than 200,000 Americans and looked for virus-fighting antibodies made from infections, not vaccines¹. They found that signs of past infection rose dramatically between December and February, when the more contagious² Omicron variant³ surged through the US.

研究人员检测了超20万美国人的血样，从中寻找感染病毒而非接种疫苗产生的抗击病毒的抗体。他们发现，曾感染病毒的迹象在12月至2月期间急剧增多，这段时间也是传染性更强的奥密克戎毒株在美国各地肆虐的时期。

 

For Americans of all ages, about 34% had signs of prior infection in December. Just two months later, 58% did.

在所有年龄段的美国人当中，约有34%在12月表现出曾感染病毒的迹象。仅仅两个月之后，就有58%表现出曾感染病毒的迹象。

 

"I did expect it to increase. I did not expect it to increase quite this much,” said Dr Kristie Clarke, co-leader of a CDC team that tracks the extent of coronavirus infections.

追踪新冠病毒感染范围的美疾控中心团队的共同负责人克里斯蒂·克拉克博士称：“我预期感染人数会增多。但我没想到会增加这么多。”

 

In the CDC report, the most striking increase was in children. The percentage of those 17 and under with antibodies rose from about 45% in December to about 75% in February.

在美疾控中心的这份报告中，感染人数增加最多的是儿童。17岁以下人群（含17岁）携带（感染病毒产生的）抗体的比例从12月的45%左右增加到了2月的75%左右。

 

The older people were, the less likely they had evidence of past infections. That may be because older adults have higher vaccination⁴ rates and they may be more likely to take other Covid-19 precautions, such as wearing masks and avoiding crowds, Clarke said.

年龄越大，出现曾感染病毒迹象的可能性越低。克拉克说，这可能是因为年龄大的成年人疫苗接种率更高，也更可能采取佩戴口罩和避免聚集等其他新冠预防措施。

 

Reported cases had a huge surge in December and January, then fell almost as dramatically as they had risen. But daily case counts have been trending up again in recent weeks.

美国报告的病例在12月和1月激增，之后又以几乎同样的速度剧减。但是单日新增病例数在最近几周又开始有上升趋势。

 

The case numbers are believed to be an undercount, but officials do think recent increases reflect a true rise in infections. Many Covid-19 infections are mild enough that patients do not seek care or confirmatory lab tests. CDC officials say they plan to release a study soon that estimates that in recent months there were three infections for every reported case.

实际病例数据信被低估，但是官员认为最近增加的病例数真实反映出感染人数的上升趋势。许多新冠感染病例症状都很轻微，因此患者没有就医或做核酸检测。美疾控中心官员表示，他们计划在近期发布一项研究结果，据该研究估算，近几个月以来每报告1例新增病例，实际新增感染人数为3人。

 

Another recent trend: US health officials say they have seen two weeks of increases in Covid-19 hospitalizations, though the numbers remain relatively⁵ low. Hospital admissions number about 1,600 per day, a 9% increase in the prior week, the CDC reported.

近期还有另一个趋势：美国卫生部官员称，新冠住院人数已经连续两周呈增长趋势，尽管住院人数依然相对较低。美疾控中心报告称，目前新增住院人数约为每天1600人，相比前一周增加了9%。

 

Available evidence nevertheless offers reason to be hopeful about how the pandemic is going, officials suggested.

不过，美疾控官员指出，就现有的迹象来看，他们有理由对新冠疫情的走向抱有希望。

 

"We are not anticipating more severe disease from some of these subvariants, but we are actively⁶ studying them,” said Dr Rochelle Walensky, CDC director, on Tuesday.

 

美疾控中心主任罗谢尔·瓦伦斯基博士4月26日表示：“我们认为新冠病毒目前的几个变种应该不会导致更严重的疾病，但是我们正在积极对其进行研究。”

 

The study looked for any detectable⁷ level of antibodies; it did not distinguish how many people had antibody levels that might be protective. Scientists are still trying to understand what role these kinds of antibodies play in protection from future virus exposures.

这项研究只是寻找任何可检测到的抗体水平，但没有分辨出多少人的抗体水平可能具有保护作用。科学家仍在试图理解这些抗体对于防范未来被病毒感染所发挥的作用。

 

Officials continue to urge Americans to get vaccines and boosters, which offer additional protection against Covid-19 for all, including those who were previously⁸ infected.

美疾控中心官员仍在继续敦促美国人接种疫苗和加强针，疫苗能为所有人提供针对新冠病毒的额外防护作用，包括那些感染过病毒的人。

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