世界衛生組織使用「X疾病」一詞來指稱有可能引發下一次流行病或新的全球大流行病的感染
克萊爾.威爾遜 / 2024 年 1 月 17 日 / 健康 / 新科學家
病毒的微觀視圖 圖片來源：cokada/Getty Images
什麼是疾病 X？
請勿恐慌! X 疾病目前還不存在——但有一天可能會出現。 X 病是世界衛生組織用來指稱某些目前未知的傳染病的標誌，這些傳染病可能引起流行病，或者如果它在多個國家傳播，則可能導致大流行。 該術語於 2017 年創造，可用於指新發現的病原體或任何具有新獲得大流行潛力的已知病原體。 根據後者定義，covid-19 是第一種 X 疾病。但未來可能還會出現另一種疾病。
為什麼現在人們都在談論它？
世界衛生組織在本週於瑞士達沃斯舉行的世界經濟論壇年會上一直就未來流行病的風險向全球領導人發出警告。 世衛組織總幹事譚德塞表示：「有些人說這可能會造成恐慌」。 「不。 最好預測可能發生的事情——因為它在我們的歷史上已經發生過很多次——並做好準備」。
下一個疾病 X 可能是什麼？
我們不知道——這就是為什麼它被稱為「X 病」。冠狀病毒是一大類病毒，甚至在 covid-19 爆發之前就一直被視為引發新的大流行的主要競爭者。 這是因為新型冠狀病毒並不是該群體中第一個危險的病原體。 2002年，另一種冠狀病毒開始在中國傳播。 它引發了一種名為「SARS」的肺炎，在嚴格的感染控制措施阻止其傳播之前，大約十分之一的感染者因此死亡。 另一種更致命的冠狀病毒偶爾會爆發，稱為中東呼吸道症候群（MERS），引起肺炎，導致三分之一的感染者死亡。 然而，最近的研究顯示，SARS 和MERS 很難引發新的大流行，因為現在世界上幾乎每個人都擁有針對導致covid-19 的病毒的抗體，而這些抗體似乎可以部分保護冠狀病毒家族中的大多數其他病原體。
還有其他具有大流行潛力的競爭者嗎？
許多疾病，有些是眾所周知的，有些是不太熟悉的，可能構成全球威脅。 流感病毒株過去曾多次引發全球大流行，其中包括有史以來最致命的疾病爆發之一，即1918 年的「西班牙流感」。目前，一種致命的禽流感病毒株正在席捲全球，偶爾會從鳥類傳播到哺乳類動物，造成大規模死亡。 就在本週，它被認為是去年10月阿根廷17,000隻小象海豹死亡的罪魁禍首。 還有其他競爭者，例如伊波拉病毒（會導致嚴重出血）和蚊子傳播的玆卡病毒（如果在懷孕期間感染，可能會導致嬰兒出生時頭部較小）。 世界衛生組織更新了 2022 年最具大流行潛力的病原體清單。
我們能做些什麼來阻止X疾病？
有一些好消息：covid-19 大流行可能使阻止未來任何 X 疾病變得更容易。Covid-19 刺激了新型疫苗設計的開發，包括可以快速重新調整用途以針對新病原體的疫苗設計。 例如，它導致了基於 mRNA 的疫苗的出現。 這個配方含有一小段遺傳物質，可以使人體的免疫細胞產生冠狀病毒「棘」蛋白，但它可以透過簡單地重寫 mRNA 序列進行更新，使細胞產生不同的蛋白質。
我們還能採取其他措施來對抗 X 疾病嗎？
譚德塞表示，各國需要針對新疾病建立更好的預警系統，衛生服務也需要增強應對意外激增需求的能力。 「當醫院因新冠疫情超出其承受能力時，我們失去了很多人，因為我們無法管理他們。 沒有足夠的空間，沒有足夠的氧氣」。 譚德塞表示，為了防止 X 疾病爆發時發生同樣的情況，衛生服務機構必須能夠按需要擴大其能力。 幸運的是，他們可以在不確切知道 X 疾病是什麼的情況下進行這些準備。 「疾病 X 是一個佔位符」，他說。「無論是什麼疾病，你都可以做好準備」。
What is Disease X and why is it in the news?
The World Health Organization uses the term “Disease X” to refer to an infection with the potential for causing the next epidemic – or a new global pandemic
Clare Wilson / 17 January 2024 / Health / New Scientist
A microscopic view of viruses cokada/Getty Images
What is Disease X?
Don’t panic! Disease X doesn’t exist yet – but it might one day. Disease X is the label that the World Health Organization uses to refer to some currently unknown infectious condition that is capable of causing an epidemic or – if it spreads across multiple countries – a pandemic. The term, coined in 2017, can be used to mean a newly discovered pathogen or any known pathogen with newly acquired pandemic potential. By the latter definition, covid-19 was the first Disease X. But there could be another in the future.
Why are people talking about it now?
The World Health Organization has been warning global leaders about the risks of future pandemics at the World Economic Forum’s annual meeting, held this week in Davos, Switzerland. “Some people say this may create panic,” says WHO director-general Tedros Adhanom Ghebreyesus. “No. It’s better to anticipate something that may happen – because it has happened in our history many times – and prepare for it.”
What might the next Disease X be?
We don’t know – that is why it is called Disease X. The coronaviruses, a large group of viruses, were long seen as a prime contender for producing a new pandemic, even before the covid-19 outbreak. That is because the novel coronavirus wasn’t the first dangerous pathogen from this group. In 2002, a different coronavirus started spreading in China. It caused a form of pneumonia called SARS that killed around 1 in 10 of those it infected, before it was stopped by strict infection control measures. Another, even deadlier coronavirus called MERS occasionally breaks out, causing a pneumonia that kills 1 in 3 of those infected. However, recent work suggests SARS and MERS would have a harder time triggering a fresh pandemic because almost everyone in the world now has antibodies to the virus that causes covid-19 and these seem to give partial protection against most other pathogens in the coronavirus family.
Are there any other contenders with pandemic potential?
Plenty of diseases, some well known and others less familiar, could pose a global threat. Flu strains have caused global pandemics several times in the past, including one of the deadliest disease outbreaks ever, the “Spanish flu” of 1918. A virulent strain of bird flu is currently sweeping the world, and it occasionally spreads from birds to mammals, causing mass die-offs. Just this week, it was named as the culprit in the deaths of 17,000 baby elephant seals in Argentina last October. Then there are other contenders, such as Ebola, which causes severe bleeding, and the mosquito-borne Zika, which can cause babies to born with smaller heads if the infection occurs during pregnancy. The WHO updated its list of pathogens with the most pandemic potential in 2022.
What can we do to stop Disease X?
There is some good news: the covid-19 pandemic may have made it easier to stop any future Disease X. Covid-19 spurred the development of novel vaccine designs, including ones that can be quickly repurposed to target new pathogens. It led, for instance, to the advent of vaccines based on mRNA. This formula contains a short piece of genetic material that makes the body’s immune cells produce the coronavirus “spike” protein – but it could be updated to make cells churn out a different protein, simply by rewriting the mRNA sequence.
Can we do anything else to fight against Disease X?
Countries need better early warning systems for new diseases, and health services need to become more resilient to unexpected surges in demand, says Tedros. “When hospitals were stretched beyond their capacity [with covid], we lost many people because we could not manage them. There was not enough space, there was not enough oxygen.” To prevent the same thing from happening when Disease X strikes, Tedros says health services must be able to expand their capacity on demand. Luckily, they can make those preparations without knowing exactly what Disease X will be. “Disease X is a placeholder,” he says. “Whatever the disease is, you can prepare for it.”