瑪麗亞·伊莎貝爾·巴羅斯·金勒 / 2024 年 11 月 20 日 / 不斷變化的世界中的生活故事 /
山羊和蘇打水（美國國家公共廣播電台之全球衛生與發展的部落格）
一名衛生工作者正在對哈瓦那一棟大樓的地下室進行薰蒸，古巴衛生當局正在進行小規模的努力，以遏制透過蠓和蚊子叮咬傳播的奧羅普切病毒的傳播。 諾利斯·佩雷斯//路透社
今年，一種鮮為人知的病毒引起了廣泛關注。它被稱為奧羅普切（Oroouche），由於診斷人數顯著增加而成為頭條新聞。
2024 年迄今為止，已有超過 10,000 例病例，主要發生在南美洲和加勒比海地區。絕大多數在巴西。相較之下，2015 年至 2022 年間巴西記錄的奧羅普切病例總數為 261 例。
美國疾病管制與預防中心的報告指出：「根據目前可獲得的數據，美國大陸持續本地傳播的風險可能很低，而波多黎各和美屬維京群島持續傳播的風險尚不清楚。疾病預防控制中心正在與合作夥伴合作，進一步了解當前疫情爆發的原因以及這可能如何去影響傳播風險。
八月，泛美衛生組織（PAHO）發布了流行病學警報，敦促加強對病毒感染的預防、監測和診斷，這種病毒感染是透過蚊子或蠓（一種叮咬人類的蠓科昆蟲）叮咬傳播的。
現在有一個新的擔憂。疾病預防控制中心在十月份的《新興傳染病》雜誌上發表的一項研究報告稱，性接觸可能是傳播病毒的一種方式。
「這是一個非常大的進展」，南非斯泰倫博斯大學流行病應對與創新中心主任圖利奧·德奧利維拉博士說道，他並沒有參與這項研究。
與蠓的關聯
該病毒於 1955 年首次被發現，並以發現病毒的特立尼達村莊命名。發音：“o-ro-push”。
奧羅普切病毒棲息在鳥類、猴子、囓齒類和樹懶體內。它是一種蟲媒病毒，就像登革熱、玆卡（Zika）病毒和屈公熱（Chikungunya）一樣——該術語指的是昆蟲叮咬引起的任何疾病。如果蚊子或蠓（一種小型蠓科昆蟲）叮咬受感染的小動物，然後去吸食人類的血，病毒就會紮根。
蠓傳播這種疾病的事實是一個嚴重的問題。美國疾病預防控制中心國家新興和人畜共通傳染病中心副主任克里斯·布雷登博士說：「這叮咬的蠓被稱為『no-see-ums』」 。 「它們太小了，實際上可以飛過標準的紗窗」。長期以來，它們一直被認為是一種令人討厭的東西，被叮咬後會留下發癢的傷痕或引發過敏反應。但認識到它們可以傳播傷害人類的病毒，使對這叮咬的蠓之擔憂上升到了一個新的水平。它們是一種新興的疾病媒介，尚未被充分研究。
如果你被叮咬並感染病毒會發生什麼事？奧羅普切感染的症狀是許多病毒的典型症狀，通常持續一週：發燒、皮疹、肌肉酸痛、頭痛。但有些情況可能更嚴重，導致腦炎和腦膜炎——大腦及其周圍的腦膜發炎，導致腦部腫脹。與玆卡病毒一樣，母親可以在懷孕期間將病毒傳播給胎兒，這可能導致出生缺陷甚至胎兒死亡。
「已經有幾例母嬰傳播病例，並且有四例先天性奧羅普切感染病例，所有這些都導致了小頭畸形，即頭部尺寸較小」，波士頓大學公共衛生學院全球健康與醫學博士、教授暨傳染病專家戴維森·哈默博士說道。 「真正可怕的是[發生了]流產，最近還出現了死產」，他補充道。
「這名產婦（死產）正處於懷孕中期，出現了發燒和典型的登革熱症狀，也是奧羅普切病的典型症狀，幾天后，她的孩子停止了活動。所以她去做了超音波檢查，結果顯示她的孩子已經死了」，傳染病醫生描述道。「他們從多個組織中進行了活檢，並在各處取樣，[他們發現了]奧羅普切病毒」。
性傳播
現在有新的證據顯示奧羅普切病毒還可以透過另一種方式傳播：透過性行為。
2024年8月2日，一名7月19日至29日去過古巴的男子在義大利一家醫院被診斷出患有奧羅普切病。他在古巴的最後一天發燒了。在他康復期間，研究人員使用 PCR 檢測，在他的血液、尿液和精液中尋找病毒。令他們驚訝的是，他們不僅在症狀出現 16 天後（以及症狀完全消失後 6 天）在他的精液中發現了病毒，而且還發現該病毒仍然能夠複製並傳播。
斯泰倫博斯大學的圖利奧·德奧利維拉博士說：「這可以開闢一條新的傳播途徑」。
該研究是在義大利維羅納的 Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Sacro Cuore Don Calabria 醫院進行的。結果非常令人擔憂，以至於該研究結果成為早期發布的文章，發表在美國疾病管制與預防中心的《新興傳染病》雜誌上。根據疾病預防控制中心的說法，早期發布的出版文章是為「具有緊急公共衛生重要性」的研究而保留的。
「這種[性傳播的可能性] 所帶來的問題多於答案」，哈默博士說，他的合作者參與了這項研究。
但哈默博士強調，我們尚未有記錄的性傳播病例。我們現在所知道的是，性傳播可能會發生——但目前並未發生。
儘管如此，這種性傳播的可能性已經足夠嚴重，以至於疾病預防控制中心 (CDC) 在11 月4 日發布了臨時指南，建議前往奧羅普切1 級或2 級旅行健康警示地區後，出現奧羅普切症狀的男性旅行者，「從症狀出現起至少達 6 週的期間」，於性行為時應考慮是否使用保險套或暫停性行為。
疾病預防控制中心網站上的聲明中寫道：「由於死產、出生缺陷以及成人嚴重併發症和死亡的報道，疾病預防控制中心正在根據我們目前所知的情況，提供預防可能的性傳播之臨時建議。
森林毀壞的角色
這種新的潛在傳播途徑並不能解釋哈默博士所說的「病例激增」。
「案件數量比往年增加了大約 60 倍」，他說。
該病毒最初僅限於亞馬遜河流域。即使在巴西的流行中心，2015 年至 2022 年間每年報告的奧羅普切病例也不到 100 例。 「所以，發生了一些變化——已發生了一些事情」，傳染病醫生說。
德奧利維拉博士認為森林砍伐可能是部分原因。當樹木被砍伐、人們搬進來（通常是為了耕種）時，他們會與生活在亞馬遜森林中的哺乳動物以及叮咬它們的蚊子和蠓蟲密切接觸。
「所以現在在蠓和哺乳動物之間傳播的病毒[已經接近]人類」，他說。 「然後這些人就獲得了病毒，而他們會做什麼呢？他們會[來回] 地前往大城市。
這可能會導致病毒傳播給更多人。如果任何感染者前往其他國家/地區，那麼病毒也可能在那裡傳播。
更新、更強的病毒株
森林砍伐並不是幫助奧羅普切蓬勃發展的唯一因素。哈默博士說，我們現在有證據顯示，病毒本身可能透過一種稱為病毒片段重組（reassortment）的過程發生了變化。
他解釋說，片段重組是分段型病毒（如 Oropouche）創造新株的一種方式。顧名思義，分段型病毒由多個較小的片段或單元組成。您可以將它們視為病毒的可分離片段。如果兩種分段型病毒感染同一個細胞，它們可以混合和匹配它們的片段以創建新的混合版本。這種混合版本就是所謂的病毒新株。
巴西傳染病研究人員在十月於《刺胳針》上發表的一項研究發現，奧羅普切病毒已經發生了巨大的變化，以至於過去對它有免疫力的人不再有免疫力。 「基本上，這顯示該病毒已經發生了片段重組，與之前傳播的病毒有很大不同」，哈默博士解釋說。
「那些對過去的感染有免疫力的人——5、10年前——他們可能會再次被感染」。
這種版本的病毒不僅可以感染以前免疫過的人，而且可能比以往任何時候都更快地感染人，這解釋了當前前所未有的傳播。 「看起來它生長得更快——它可能是一種毒性更強的病毒株」，哈默博士說。
展望未來
兩位專家都不認為我們正處於全球疫情爆發的邊緣。 de Oliveira 博士領導的團隊首次在南非檢測到了COVID-19的omicron 變異株，「我們對奧羅普切 [Oropoouche] 感到警惕，但還不擔心它會導致全球爆發」。
「挑戰在於，這是一種新疾病，大多數臨床醫生——包括傳染病專家——都沒有意識到它，我們需要讓更多的患者和醫療保健提供者意識到這種疾病，並增加獲得診斷的機會，以便我們能夠為此進行測試」，哈默博士說。 「在接下來的一年裡，我們將學到更多」。
NPR 記者Pien Huang 對本文做出了貢獻。
2024 年11月 21 日更正
這篇文章的早期版本展示了一張蠓幼蟲的照片。影像中的蠓——幻影蠓——不會叮咬人類。
It’s a virus you may not have heard of. Here’s why scientists are worried about it
Maria Isabel Barros Guinle / November 20, 2024 / STORIES OF LIFE IN A CHANGING WORLD /
Goats and Soda
A health worker fumigates the basement of a building in Havana as Cuban health authorities launch small-scale efforts to fight the spread of the oropouche virus, which is transmitted by midge and mosquito bites. Norlys Perez//Reuters
A little-known virus is getting a lot of attention this year. It’s called Oropouche, and it’s been making headlines because of a notable increase in diagnoses.
So far in 2024 there have been over 10,000 cases, mainly in South America and the Caribbean. The vast majority are in Brazil. By contrast, the total Oropouche count in Brazil recorded between 2015 and 2022 was 261. Of the 21 recorded cases in the United States, all involved an individual who had traveled to Cuba and contracted the virus there.
A report from the Centers for Disease Control and Prevention notes: “Based on presently available data, the risk for sustained local transmission in the continental United States is likely low, whereas the risk for sustained transmission in Puerto Rico and U.S. Virgin Islands is unknown. CDC is working with partners to understand more about what is driving the current outbreaks and how that might affect risk of transmission.”
In August, PAHO, the Pan American Health Organization, issued an epidemiological alert urging for increased prevention, surveillance and diagnosis of the viral infection, which is spread by the bite of a mosquito or a midge (a kind of fly that bites humans).
Now there’s a new concern. A study published in the CDC’s journal, Emerging Infectious Disease in October reports that sexual contact might be a way to transmit the virus.
“This is a very big development,” says Dr. Tulio de Oliveira, director for the Center of Epidemic Response and Innovation at Stellenbosch University in South Africa, who was not involved in the study.
The midge connection
The virus was first identified in 1955 and named for the village in Trinidad where it was found. The pronounciation: “o-ro-push.”
Oropouche is harbored in birds, monkeys, rodents and sloths. It’s an arbovirus like dengue, Zika and Chikungunya –—the term refers to any disease caused by insect bites. If a mosquito or a midge — a tiny fly – bites an infected critter and then goes for a blood meal from a human, the virus can take root.
The fact that midges spread it is a serious issue. “Biting midges are known as ‘no-see-ums,’ ” says Dr. Chris Braden, deputy director of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases. “They’re so small they can actually fly through standard window screens.” They’ve long been considered a nuisance, leaving itchy welts or spurring allergic reactions with their bites. But this understanding that they can transmit a virus that harms humans raises biting midges to a new level of concern. They’re an emerging disease vector that hasn’t been well-studied.
And what happens if you get a bite and catch the virus? Symptoms of Oropouche infection are typical of many viruses and usually last a week: fever, rash, muscle aches, headache. But some cases can be more severe, causing encephalitis and meningitis —inflammation of the brain and its surrounding membrane that can cause it to swell. And as with Zika, a mother can transmit the virus to the fetus during pregnancy — which can lead to birth defects and even fetal death.
“There have been a few cases of maternal to fetal transmission, and there are four cases of congenital Oropouche infections that have been described — all of which led to microcephaly, which is a small head size,” said Dr. Davidson Hamer, infectious disease doctor and professor of Global Health and Medicine at Boston University School of Public Health. “What is really scary is that [there has been a] miscarriage and most recently a stillbirth,” he added.
“This woman [who had a stillbirth] was in her mid-pregnancy and developed a fever and symptoms typical of dengue but also typical of Oropouche and then a couple days later her baby stopped moving. So she went and got an ultrasound done and it showed her baby had died,” described the infectious disease doctor. “They took biopsies from multiple tissues and everywhere they sampled [they found] Oropouche virus.”
Sexual transmission
And now there’s the new evidence suggesting that Oropouche could spread in yet another way: through sex.
On August 2, 2024, a man who had been in Cuba from July 19 to 29 was diagnosed with Oropouche in a hospital in Italy. He had developed a fever his last day in Cuba. During his recovery, researchers used PCR tests to look for the virus in his blood, urine and semen. To their surprise, they not only found the virus in his semen 16 days after his symptoms started — and 6 days after they had completely resolved — but they also found that the virus was still able to replicate and spread.
“This can open a new route of transmission,” said Dr. Tulio de Oliveira of Stellenbosch University.
The study was conducted in the Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Sacro Cuore Don Calabria Hospital in Verona, Italy. The results were concerning enough that the findings were published as an early release article in the Center for Disease Control and Prevention’s Emerging Infectious Diseases journal. According to the CDC, early release publications are reserved for studies “with urgent public health importance.”
“This [possibility of sexual transmission] brought up more questions than answers,” said Dr. Hamer, whose collaborators were involved in the study.
But Dr. Hamer emphasized that we have no documented cases of sexual transmission yet. What we know now is that sexual transmission could happen — not that it has.
Nonetheless, this potential for sexual transmission was serious enough for the CDC to issue a provisional guidance on November 4th, recommending that male travelers who develop Oropouche symptoms after visiting areas with Level 1 or 2 Travel Health notices for Oropouche to “consider using condoms or not having sex for at least 6 weeks” from the start of their symptoms.
“Because stillbirths, birth defects, and severe complications and deaths in adults have been reported, CDC is providing interim recommendations on preventing possible sexual transmission based on what we know now,” reads the statement in the CDC website.
The role of deforestation
This new potential route of transmission doesn’t explain what Dr. Hamer described as “an explosion of cases.”
“The number of cases is something like 60 times higher than in previous years,” he says.
The virus was initially confined to the Amazon Basin. Even in the epicenter of Brazil, fewer than 100 cases of Oropouche per year were reported between 2015 and 2022. “So, there’s been some change — something’s happened,” said the infectious disease doctor.
Dr. de Oliveira thinks deforestation may be partly to blame. When trees are felled and people move in, typically to farm, they come into close contact with the mammals that live in the Amazon forests — and the mosquitoes and midges that bite all of them.
“So now the virus that was circulating between midges and mammals [is near] people,” he says. “And then these people acquire the virus, and what do they do? They [travel back and forth] to the big cities.”
That can result in the spread of the virus to more people. And if anyone who’s infected travels travel to a different country, then the virus can spread there as well.
A newer, stronger strain
Deforestation isn’t the only factor helping Oropouche thrive. Dr. Hamer said that we now have evidence that the virus itself may have changed through a process called viral reassortment.
He explains that reassortment is one way that segmented viruses — like Oropouche – create new strains. As the name implies, segmented viruses are made up of multiple smaller segments — or units. You can think of these as detachable pieces of the virus. If two segmented viruses infect the same cell, they can mix and match their segments to create a new, hybrid version. This hybrid version is what you would call a new strain of the virus.
A study by Brazilian infectious disease researchers published on The Lancet in October found that the Oropouche virus has changed so much that people who had immunity to it in the past no longer do. “Basically, it suggested that the virus has undergone a reassortment and it is very different from what had been circulating previously,” explains Dr. Hamer. “People who had immunity from past episodes — 5, 10 years ago — they could become infected again.”
And not only can this version of the virus infect people who had been immune before, it may infect people faster than ever before — explaining the current unprecedented spread. “It looks like it grows much more rapidly – it might be a more virulent strain of the virus,” says Dr. Hamer.
Looking ahead
Neither expert thinks we are on the brink of a global outbreak quite yet. “We are alerted about [Oropouche] but not concerned that it will cause a global outbreak yet,” says Dr. de Oliveira who led the team that first detected the omicron variant of COVID-19 in South Africa.
“The challenge is that this is such a new disease that most clinicians — including infectious disease specialists — are not aware of it and we need to make more patients and health-care providers aware of the disease and increase access to diagnostics so we can test for it,” says Dr. Hamer. “Over the next year, we are going to learn a lot more.”
NPR correspondent Pien Huang contributed to this story.
CorrectionNov. 21, 2024
An earlier version of this post displayed a photograph of a midge larva. The midge in the image — the phantom midge — does not bite humans.