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    奧密克戎雙亞型正在肆虐美國,其中一種傳染性最強

    奧密克戎雙亞型正在肆虐美國,其中一種傳染性最強

    Erin Prater 2022-06-30
    新病毒大幅降低了疫苗對重癥的防護能力。

    2022年6月21日,美國總統喬·拜登在華盛頓特區的圣餐教堂新冠病毒疫苗接種診所里與孩子們打招呼。圖片來源:NICHOLAS KAMM / AFP VIA GETTY IMAGES

    根據6月28日公布的聯邦健康數據,兩種能夠逃避免疫系統的奧密克戎亞型變異株目前在美國占據主導地位,在短短幾周內就超過了所謂的“隱形奧密克戎”和相近的亞型變異株BA.2.12.1。

    美國疾病控制和預防中心(U.S. Centers for Disease Control and Prevention)的新數據顯示,今年春天,BA.4和BA.5因為其逃避免疫系統的能力而席卷南非,據估計,上周在美國造成了略多于一半(52%)的人感染新冠病毒。

    斯克利普斯研究所(Scripps Research)的分子醫學教授、斯克里普斯研究轉化研究所(Scripps Research Translational Institute)的創始人及所長埃里克·托波爾博士于6月27日在預期病毒會肆虐時寫道:“奧密克戎亞型變異株BA.5是我們見過的傳染性最強的毒株?!?/p>

    他說:“它將已經廣泛的免疫逃逸提升到新水平,增強了傳播能力?!边h遠超出我們以前所看到的情況?!澳憧梢哉f,情況沒有那么糟糕,因為住院和死亡人數不像我們看到的奧密克戎感染病例那樣顯著上升,但那只是因為奧密克戎毒株帶來了嚴重影響,而且至少有一些交叉免疫的情況出現?!?/p>

    BA.2.12.1是另一個在BA.4和BA.5出現之前占據主導地位的奧密克戎亞型變異株,占確診病例數的42%。所謂的隱形奧密克戎, BA.2,因為其逃避核酸檢測的能力而得名,排在第三位,占確診病例數的近6%。隱形奧密克戎此前一直在美國占據主導地位,直到今年5月BA.2.12.1超過了它,在美國占據主導地位。

    目前的疫苗是否能夠抵抗BA.5尚無定論。但考慮到從德爾塔毒株到奧密克戎毒株,疫苗對重癥的防護能力下降了大約15%,“看到疫苗對住院和死亡病例的防護能力進一步下降,我一點也不驚訝?!蓖胁枌懙?。

    正如《財富》雜志先前報道的那樣,今年3月底,美國首次發現了BA.4和BA.5。在南非發現的這兩種變異株于4月和5月迅速席卷南非,盡管當時幾乎所有南非人都接種了疫苗或之前感染過新冠病毒。

    這兩種變異株迅速席卷全球。但托波爾寫道,這兩種變異株感染病例的上升往往被掩蓋,因為在許多國家,這兩種變異株感染病例的上升與BA.2感染病例的下降同時發生。這可能會導致出現持續的疫情浪潮,而在現實中,出現的是兩波疫情潮——第一波來自較老版本的奧密克戎,第二波來自BA.4/BA.5。

    南非最近的一項研究發現,那些之前感染過奧密克戎但沒有接種疫苗的人,在感染BA.4和BA.5時,中和抗體下降了近八倍。那些接種過疫苗并在之前感染過奧密克戎的人,中和抗體下降幅度較小,下降了三倍。

    今年5月,南非非洲衛生研究所(African Health Research Institute)教授亞歷克斯·西加爾告訴《財富》雜志,感染新亞型變異株的癥狀與感染奧密克戎毒株的典型癥狀類似,包括發燒、嗅覺喪失和身體不適。

    他說:“我沒有看到呼吸困難的早期癥狀,這是讓這種疾病如此危險的新冠肺炎主要特異性癥狀。雖然感染后身體感覺不適,但死亡的幾率更小了?!保ㄘ敻恢形木W)

    譯者:中慧言-王芳

    根據6月28日公布的聯邦健康數據,兩種能夠逃避免疫系統的奧密克戎亞型變異株目前在美國占據主導地位,在短短幾周內就超過了所謂的“隱形奧密克戎”和相近的亞型變異株BA.2.12.1。

    美國疾病控制和預防中心(U.S. Centers for Disease Control and Prevention)的新數據顯示,今年春天,BA.4和BA.5因為其逃避免疫系統的能力而席卷南非,據估計,上周在美國造成了略多于一半(52%)的人感染新冠病毒。

    斯克利普斯研究所(Scripps Research)的分子醫學教授、斯克里普斯研究轉化研究所(Scripps Research Translational Institute)的創始人及所長埃里克·托波爾博士于6月27日在預期病毒會肆虐時寫道:“奧密克戎亞型變異株BA.5是我們見過的傳染性最強的毒株?!?/p>

    他說:“它將已經廣泛的免疫逃逸提升到新水平,增強了傳播能力?!边h遠超出我們以前所看到的情況?!澳憧梢哉f,情況沒有那么糟糕,因為住院和死亡人數不像我們看到的奧密克戎感染病例那樣顯著上升,但那只是因為奧密克戎毒株帶來了嚴重影響,而且至少有一些交叉免疫的情況出現?!?/p>

    BA.2.12.1是另一個在BA.4和BA.5出現之前占據主導地位的奧密克戎亞型變異株,占確診病例數的42%。所謂的隱形奧密克戎, BA.2,因為其逃避核酸檢測的能力而得名,排在第三位,占確診病例數的近6%。隱形奧密克戎此前一直在美國占據主導地位,直到今年5月BA.2.12.1超過了它,在美國占據主導地位。

    目前的疫苗是否能夠抵抗BA.5尚無定論。但考慮到從德爾塔毒株到奧密克戎毒株,疫苗對重癥的防護能力下降了大約15%,“看到疫苗對住院和死亡病例的防護能力進一步下降,我一點也不驚訝?!蓖胁枌懙?。

    正如《財富》雜志先前報道的那樣,今年3月底,美國首次發現了BA.4和BA.5。在南非發現的這兩種變異株于4月和5月迅速席卷南非,盡管當時幾乎所有南非人都接種了疫苗或之前感染過新冠病毒。

    這兩種變異株迅速席卷全球。但托波爾寫道,這兩種變異株感染病例的上升往往被掩蓋,因為在許多國家,這兩種變異株感染病例的上升與BA.2感染病例的下降同時發生。這可能會導致出現持續的疫情浪潮,而在現實中,出現的是兩波疫情潮——第一波來自較老版本的奧密克戎,第二波來自BA.4/BA.5。

    南非最近的一項研究發現,那些之前感染過奧密克戎但沒有接種疫苗的人,在感染BA.4和BA.5時,中和抗體下降了近八倍。那些接種過疫苗并在之前感染過奧密克戎的人,中和抗體下降幅度較小,下降了三倍。

    今年5月,南非非洲衛生研究所(African Health Research Institute)教授亞歷克斯·西加爾告訴《財富》雜志,感染新亞型變異株的癥狀與感染奧密克戎毒株的典型癥狀類似,包括發燒、嗅覺喪失和身體不適。

    他說:“我沒有看到呼吸困難的早期癥狀,這是讓這種疾病如此危險的新冠肺炎主要特異性癥狀。雖然感染后身體感覺不適,但死亡的幾率更小了?!保ㄘ敻恢形木W)

    譯者:中慧言-王芳

    A pair of immune-evading Omicron subvariants are now dominant in the U.S., having overtaken so-called "stealth Omicron" and close relative BA.2.12.1 in mere weeks, according to federal health data released on June 28.

    BA.4 and BA.5, which swept South Africa this spring along thanks to their ability to evade immunity, were estimated to have caused slightly more than half (52%) of COVID infections in the U.S. last week, according to new data from the U.S. Centers for Disease Control and Prevention.

    “The Omicron subvariant BA.5 is the worst version of the virus that we’ve seen,” Dr. Eric Topol, a professor of molecular medicine at Scripps Research and founder and director of the Scripps Research Translational Institute, wrote on June 27 in anticipation of the viral coup.

    "It takes immune escape, already extensive, to the next level, and, as a function of that, enhanced transmissibility," well beyond what has been seen before, he wrote. "You could say it’s not so bad because there hasn’t been a marked rise in hospitalizations and deaths as we saw with Omicron, but that’s only because we had such a striking adverse impact from Omicron, for which there is at least some cross-immunity."

    BA.2.12.1, another Omicron subvariant dominant before the advent of BA.4 and BA.5, was responsible for 42% of cases. So-called stealth Omicron, BA.2, nicknamed for its ability to evade detection on PCR tests, came in third, comprising nearly 6% of cases. It had been dominant in the U.S. until BA.2.12.1 overtook it in May.

    The jury is still out on whether current vaccines hold up against BA.5. But given that vaccines experienced an approximate 15% drop in protection against severe disease from Delta to Omicron, "it would not be at all surprising to me to see further decline of protection against hospitalizations and deaths," Topol wrote.

    BA.4 and BA.5 were first detected in the U.S. in late March, as Fortune previously reported. The variants, discovered in South Africa, quickly took hold in the country in April and May despite the fact that almost all South Africans had been vaccinated or previously had COVID by that point.

    The pair of variants are quickly taking hold globally. But their rise is often masked because in many countries, it's occurring at the same time as a decline in BA.2 infections, Topol wrote. This can lead to the appearance of a sustained wave when, in reality, dual waves are present—the first from an older version of Omicron, and the second from BA.4/BA.5.

    A recent study out of South Africa found that those who had been previously infected with Omicron but not vaccinated experienced a nearly eightfold drop in neutralizing antibodies when exposed to BA.4 and BA.5. Those who had been vaccinated and previously infected with Omicron saw a milder threefold decrease.

    Alex Sigal, a professor at the Africa Health Research Institute in South Africa, told Fortune in May that symptoms of the new subvariants are similar to typical Omicron symptoms, which include fever, loss of smell, and malaise.

    “I haven’t seen early symptoms of respiratory distress, the major COVID-specific symptom that makes this disease so dangerous,” he said. “It doesn’t feel nice, but there’s less chance of dying.”

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