盧安達疫情中首例已知馬堡病毒感染者曾參觀過一個棲息著某種特定蝙蝠的洞穴，這種蝙蝠有攜帶致命病原體的歷史。

馬克斯‧科茲洛夫 / 2024 年 10 月 24 日 / 新聞 / 自然

馬堡病毒（紅色；人工著色）從動物到人類的一次跳躍引發了盧安達的持續爆發。

初步基因組證據顯示，致命的馬堡病毒歷史上第三大爆發是由病原體從動物到人類的單次跳躍引發的。

疫情於上個月在盧安達爆發，已感染 63 人，其中 15 人死亡。其他證據顯示，疫情爆發中第一個被感染的人可能是在參觀一個洞穴時感染了這種疾病，該洞穴棲息著一種已知攜帶病毒的蝙蝠。

從動物到人類的多次傳入可能會引起人們的擔憂，即病毒在盧安達的傳播範圍比先前想像的更為廣泛。多次引入也可能增加新的疫情爆發的可能性，病毒來源不明也可能增加這種可能性。

致命的馬堡病毒：科學家競相測試爆發中的疫苗

研究人員表示，盧安達對病毒的反應也避免了疫情進一步惡化。科學家們讚揚該國為控制疫情、調查其起源以及與科學界分享數據所做的努力。「一旦他們意識到這是一個問題，他們就開始追踪接觸者，進行徹底的流行病學調查，確定了第一個患者和潛在的感染源，並設法在一周內推出了實驗性疫苗試驗」。加拿大位於薩斯卡通的薩斯喀徹溫大學的病毒學家安吉拉‧拉斯穆森說。她補充道，這顯示，對於馬堡病毒病，「快速緊急反應可以減輕疫情的嚴重程度」。

研究結果尚未完整發表或經過同行評審，已發佈在社交媒體平台 X 上，並在 10 月 20 日的媒體簡報會上進行了討論。

快速遏制

9 月 27 日宣布爆發疫情，這是盧安達首次爆發疫情；坦尚尼亞和赤道幾內亞去年記錄了首次馬堡疫情，加納首次爆發是在 2022 年。馬堡疫情會導致高燒、嚴重腹瀉、噁心和嘔吐，嚴重時會導致鼻子或牙齦出血，現在大約發生在 2022 年。每年一次。在2020年代之前，它們每十年至多被檢測到幾次。

自疫情爆發以來，新感染病例的報告已明顯減少。盧安達衛生官員在過去10天內記錄了1例新病例，沒有死亡病例，只有兩人仍在隔離和治療中。當連續 42 天沒有通報新病例時，即可宣布馬堡疫情結束。

致命馬堡病毒在盧安達呈現上升趨勢：科學家為何感到擔憂

該病毒感染尚無經過驗證的疫苗或治療方法，該病毒在症狀和傳播（主要透過體液接觸）方面與伊波拉病毒密切相關。衛生官員正在向感染者的接觸者提供由華盛頓特區薩賓疫苗研究所生產的候選疫苗。迄今為止，已注射了 1,200 多劑疫苗。

此次疫情是馬堡有史以來死亡率最低的疫情之一（約 24%）；據報道，先前爆發的死亡率高達 90%。這可能是因為診斷速度快、醫療服務可近性高，而且大多數感染者是相對年輕的醫護人員。

事實上，有兩名感染病毒並接受維生治療的人成功插管，後來康復後又拔掉了插管。瑞士日內瓦世界衛生組織秘書長譚德塞在 10 月 20 日的記者會上表示，這標誌著非洲首次為馬堡病毒病患者拔除氣管插管。 「這些患者在以前的疫情爆發中可能已經死亡」，他說。

單一來源

為了幫助控制疫情，基加利盧安達生物醫學中心的研究人員對幾名感染者的馬堡病毒基因組進行了定序。他們發現所有樣本都非常相似，這顯示病毒在短時間內迅速傳播，並且它們具有共同的起源。共同領導這項研究的盧安達衛生部長伊凡·布特拉(Yvan Butera) 告訴《自然》雜誌，他們還發現，該病毒株與2014 年在烏干達發現的一種病毒株以及2009 年在蝙蝠中發現的一種病毒株密切相關。

新冠肺炎刺激傳染病基因組定序熱潮

布特拉說，將 2014 年的毒株與導致當前疫情的毒株進行比較，顯示出「突變率有限」，這顯示在過去十年中，該病毒的傳播性或致死率可能幾乎沒有變化。一般來說，病毒會隨著時間的推移收集變異，它們會不斷複製；如果突變率確實很低，拉斯穆森想知道該病毒如何在其動物宿主——埃及果蝠 (Rousettus aegyptiacus) 中存活而沒有發生重大變化。

研究人員表示，氣候變遷和森林砍伐等環境威脅使人們更有可能遇到能夠傳播感染的動物。拉斯穆森補充說，更多關於病毒如何在蝙蝠體內持續存在以及在哪些組織中存在的數據可能有助於為監測工作提供信息，這將使衛生官員更好地了解病毒熱點。

布特拉表示，基因組分析即將完成；他說，他和他的同事希望在本週末之前分享完整的數據。

doi：https://doi.org/10.1038/d41586-024-03457-4

Animal-to-human viral leap sparked deadly Marburg outbreak

The man with the first known Marburg infection of Rwanda’s outbreak had visited a cave hosting a particular species of bat — one with a history of carrying the deadly pathogen.

Max Kozlov / 24 October 2024 / NEWS / Nature

A single jump by Marburg virus (red; artificially coloured) from an animal to humans triggered an ongoing outbreak in Rwanda.Credit: NIAID/Science Photo Library

The third-largest outbreak in history of the deadly Marburg virus was sparked by a single jump of the pathogen from an animal to humans, preliminary genomic evidence shows.

The outbreak began last month in Rwanda, where it has infected 63 people of whom 15 have died. Other evidence suggests that the first person to become infected in the outbreak probably contracted the disease during a visit to a cave that hosts a species of bat known to harbour the virus.

Multiple introductions from animals to humans would have raised fears that the virus is more widespread in Rwanda than was previously thought. Multiple introductions could also have raised the prospect of new outbreaks, as could an unknown provenance for the virus.

Deadly Marburg virus: scientists race to test vaccines in outbreak

Rwanda’s response to the virus has also kept the outbreak from being even worse, researchers say. Scientists praise the country’s efforts to control the outbreak, investigate its origins and share data with the scientific community. “As soon as they realized it was a problem, they started contact tracing, conducted a thorough epidemiological investigation, identified the [first] patient and potentially the source of the infection — and managed to roll out an experimental vaccine trial within a week,” says Angela Rasmussen, a virologist at the University of Saskatchewan in Saskatoon, Canada. This shows that, with the Marburg virus disease, “a rapid urgent response can mitigate severity of the outbreak”, she adds.

The findings, which have not yet been published in full or peer reviewed, were posted on the social-media platform X and discussed at a media briefing on 20 October.

Quick containment

The outbreak, which was declared on 27 September, is Rwanda’s first; Tanzania and Equatorial Guinea recorded their first Marburg outbreaks last year, and Ghana’s first was in 2022. Outbreaks of Marburg — which causes high fever, severe diarrhoea, nausea and vomiting, and in severe cases, bleeding from the nose or gums — now occur about once a year. Before the 2020s, they were detected at most a few times each decade.

Since the outbreak began, reports of new infections have dropped off notably. Rwandan health officials have recorded one new case and no deaths in the past 10 days, and only two people remain in isolation and treatment. A Marburg outbreak can be declared over when no new cases have been reported for 42 consecutive days.

Lethal Marburg virus is on the rise in Rwanda: why scientists are worried

There is no proven vaccine or treatment for infections with the virus, which is closely related to Ebola virus, both in its symptoms and in its transmission, which is primarily through contact with bodily fluids. Health officials are offering a candidate vaccine, made by the Sabin Vaccine Institute in Washington DC, to the contacts of infected individuals. More than 1,200 doses have been administered so far.

This outbreak has one of the lowest fatality rates — about 24% — on record for Marburg; previous outbreaks reported fatality rates as high as 90%. This is probably a result of there being quick diagnoses, access to medical care and that most infections are in relatively young health-care workers.

In fact, two people who were infected with the virus and put on life support were successfully intubated and later extubated as they recovered. This marks the first time that people with Marburg virus disease have been extubated in Africa, Tedros Adhanom Ghebreyesus, director-general of the World Health Organization in Geneva, Switzerland, said at a briefing on 20 October. “These patients would have died in previous outbreaks,” he said.

Single source

To help inform outbreak control, researchers at the Rwanda Biomedical Centre in Kigali sequenced the Marburg virus genome of several infected people. They found that all samples closely resembled one another, suggesting that the virus spread rapidly in a short period of time and that they shared a common origin. They also found that the virus strain is closely related to one detected in Uganda in 2014 and to one found in bats in 2009, Yvan Butera, Rwanda’s minister of state for health, who co-led the research, tells Nature.

COVID spurs boom in genome sequencing for infectious diseases

Comparison of the 2014 strain with the one causing the current outbreak shows a “limited mutation rate”, Butera says, suggesting that there have probably been few changes to the virus’s transmissibility or lethality over the past decade. Generally, viruses collect mutations as they replicate over time; if it is true that the mutation rate is low, Rasmussen wonders how the virus lingers in its animal reservoir — the Egyptian fruit bat (Rousettus aegyptiacus) — without major changes.

Researchers say that environmental threats, such as climate change and deforestation, have made people more likely to encounter animals that can pass on infections. More data on how the virus persists in bats — and in which tissues it does — could help to inform surveillance efforts, which would give health officials a better picture of virus hotspots, Rasmussen adds.

Butera says that the genomic analyses are being finalized; he and his colleagues hope to share the full data by the end of the week, he says.

doi: https://doi.org/10.1038/d41586-024-03457-4