非洲的猴痘：被世界所忽視的科學

資料來源：新聞 / 2022 年 6 月 23 日 / 自然期刊 / 財團法人台灣紅絲帶基金會編譯

多年來，非洲研究人員一直在警告猴痘爆發。隨著疫苗在全球範圍內部署，他們擔心自己會被拋在後面。

 

2018 年，一名婦女和她的孩子在中非共和國無國界醫生組織營運的設施中等待治療猴痘。

圖片來源：Charles Bouessel/AFP/Getty

 

上個月在葡萄牙、西班牙和英國等國家爆發猴痘病例後——這些國家通常不會發生疫情——隨後出現了快速的全球反應，包括在一些國家分發疫苗。但多年來，中非和西非部分地區一直爆發猴痘疫情，讓那裡的非洲研究人員感到沮喪的是，他們的國家沒有提供此類資源，因為那裡造成的疾病人數最多。他們指出，長期以來，他們一直在警告猴痘病毒有可能以新的方式傳播，並且可能會更廣泛地傳播。

 

猴痘疫苗接種開始——全球疫情能否得到遏制？

 

今年到目前為止，中非和西非以外的國家已經有超過3000例確診的猴痘病例，但沒有死亡報告。然而，在非洲，衛生官員報告了 70 多例死亡病例，他們懷疑是由猴痘引起的。奈及利亞阿馬索馬尼日爾三角洲大學的傳染病醫生 Dimie Ogoina 說，由於檢測和監測能力有限，這可能被低估了。

儘管他對西方國家迄今為止基本上忽視了猴痘感到沮喪，但Ogoina擔心當前的全球疫情仍不會改善非洲的情況。「如果我們不為此引起世界的關注，許多解決方案將解決歐洲的問題，而不是非洲的問題」，他說。

爆發經驗

今年之前，在非洲以外地區只觀察到少數猴痘病例；這些與從非洲大陸進口動物或到訪過疫區的旅行者有關。其中最大的一次暴發是 2003 年在美國發生的一次短暫的爆發，該爆發源於進口動物，導致 70 多人患病。

 

猴痘走向全球：科學家為何保持警惕

 

與此同時，自 1970 年科學家在剛果民主共和國 (DRC) 發現首例人類病例以來，一些非洲國家一直在應對猴痘疫情。儘管研究人員仍不清楚哪些動物自然攜帶病毒，但他們確實知道它在許多囓齒動物中傳播，並可以從動物傳播給人類。 2017 年，奈及利亞爆發了一場重大疫情，有 200 多例猴痘確診病例和 500 例疑似猴痘病例。在過去的十年裡，剛果民主共和國已經看到了數千起疑似病例，以及數百起疑似死亡病例。在中非，感染人的猴痘病毒株毒性更強，死亡率約為10%。

對於阿布賈奈及利亞疾病控制中心的流行病學家 Adesola Yinka-Ogunleye 來說，當前的全球疫情已經帶來了某種似曾相識的感覺。在 2017 年奈及利亞爆發之前，該病毒似乎僅限於農村地區，獵人會在那裡與動物接觸。它會以發燒和面部、手部和腳部獨特的充滿液體的「痘」病變而聞名。 2017 年之後，她和其他流行病學家警告，病毒正在以一種不熟悉的方式傳播：它出現在城市環境中，感染者有時會出現生殖器損傷，這表明病毒可能通過性接觸傳播。她說，隨著病毒現在通過似乎與性伴侶的密切接觸在西方城市擴散，「世界正在為 2017 年沒有做出充分反應付出代價」。

免疫力下降

與此同時，研究人員一直警告說，撒哈拉以南非洲的猴痘病例多年來一直在上升。部分原因是各國停止向人們提供天花疫苗，天花是由天花病毒引起的，天花是一種與引起猴痘的病毒密切相關的病毒。天花在 1980 年被根除，疫苗接種也停止了，這意味著易受天花影響的人口比例——以及猴痘——一直在增長（參見「非洲猴痘病例上升」）。

非洲猴痘病例上升

 

 

從那時起，一些國家一直在國家儲備天花疫苗，因為衛生官員一直擔心保存天花樣本的實驗室可能會意外釋放天花，或者該病毒可能被武器化。包括加拿大、法國、英國和美國在內的國家一直在將這些庫存用於「環形疫苗接種」策略，以保護感染猴痘病毒的人的密切接觸者。加拿大多個城市和英國的當局承認迄今為止發生了許多男男性行為者 (MSM) 病例，因此更進一步，開始向其 MSM 社區提供疫苗。

金薩沙大學的病毒學家史蒂夫·阿胡卡（Steve Ahuka）表示，這些疫苗將有助於應對非洲的疫情——但那裡的國家沒有大量庫存，西方國家也沒有捐贈他們的疫苗以用於對抗非洲猴痘。 Ahuka 和 Yinka-Ogunleye 都表示，如果他們確實有疫苗，他們至少會建議為一線醫護人員和實驗室技術人員接種疫苗。 《自然》期刊採訪的其他研究人員也表示，如果將這些疫苗用於免疫系統受損的人和經常遇到野生動物的人，這些疫苗可能有助於遏制非洲的猴痘。

缺乏投資

撒哈拉以南非洲的一些衛生官員擔心，從他們在 COVID-19 大流行期間疫苗不公平的經歷來看，他們將繼續被拋在後面。儘管病例數在上升，但非洲只有 18.4% 的人接種了冠狀病毒 SARS-CoV-2 疫苗，而其他高收入國家的這一比例為 74.8%。

 

猴痘爆發：研究人員提出的 4 個關鍵問題

 

世界衛生組織 (WHO) 的成員國已承諾向該機構提供超過 3,100 萬劑天花疫苗以應對天花緊急情況——但這些疫苗從未分發到非洲用於防治猴痘。世衛組織猴痘技術負責人羅莎蒙德·劉易斯（Rosamund Lewis）說，部分原因是該機構承諾的一些儲備是由「第一代」疫苗組成的。這些可能會產生嚴重的副作用，不推薦用於猴痘，因為猴痘的致命性低於天花。 （Lewis拒絕具體說明世衛組織承諾儲備的確切組成。）

她還引用了「監管問題」，因為一些成員國已批准疫苗僅用於對抗天花，而不是猴痘。 （儘管這些疫苗被認為可安全有效地用於天花感染者，但它們針對猴痘的測試有限。）

「這項投資可能不是我們想要的，但也不是什麼都沒有」，Lewis談到非洲應對猴痘的努力時說。她補充說，世界衛生組織一直在與爆發猴痘的非洲國家進行協調，以改善監測和診斷。

最近幾週，世界衛生組織已經認識到猴痘在全球受到關注上的不公平。 6 月 17 日，該機構宣布將不再分別報告撒哈拉以南非洲和世界其他地區的猴痘病例和死亡人數，以反映「需要統一應對」。在研究人員發表了一項更改猴痘病毒株名稱的提議後——目前稱為西非分支和剛果盆地分支——世衛組織總幹事譚德塞支持這些變化，以減少恥辱感。他承諾「盡快公佈新名字」。

 

天花和其他病毒比懷疑更早地困擾著人類

 

然而，奈及利亞伊巴丹的獨立病毒學家 Oyewale Tomori 說，即使撒哈拉以南非洲國家採購疫苗，單靠接種也無法根除猴痘。他警告說，只有在衛生官員了解當地病原體的流行病學情況下，疫苗接種才有效——而且關於這種疾病的孤立病例如何繼續在撒哈拉以南非洲受影響的國家出現仍然存在許多問題。他建議支持研究猴痘動物宿主的研究，以便衛生官員能夠制定更精確的措施來遏制病毒的傳播。他說：「如果不解決根本問題，最終你將把所有疫苗都用於猴痘」，而不是處理問題的根源——野生動物和人類之間的接觸上。

Ogoina 說，加快猴痘檢測的策略同樣重要，因為越快確診病例，公共衛生官員就越早開始採取遏制措施。他補充說，對於撒哈拉以南非洲來說，這些進步還不夠快。他警告說：「只為發達國家解決問題而將發展中國家排除在外的孤立解決方案將導致我們再次經歷相同的循環」，他指出過去的疫情中病原體繼續重新出現。「這只是時間問題」。

 

doi：https://doi.org/10.1038/d41586-022-01686-z

參考文獻：

1.Yinka-Ogunleye, A. et al. Lancet Infect. Dis. 19, 872-879 (2019).

 

Monkeypox in Africa: the science the world ignored

                                NEWS / 23 June 2022 / Nature

African researchers have been warning about monkeypox outbreaks for years. As vaccines are deployed globally, they worry they will be left behind.

 

A woman and her child await treatment for monkeypox at a facility run by Doctors Without Borders in the Central African Republic in 2018.Credit: Charles Bouessel/AFP/Getty

After monkeypox cases exploded last month in countries such as Portugal, Spain and the United Kingdom — where outbreaks don’t usually occur — a rapid, global response followed, including the distribution of vaccines in some countries. But monkeypox outbreaks have been occurring in parts of Central and West Africa for years, leaving African researchers there disheartened that such resources have not been made available in their countries, where the disease’s toll has been highest. They point out that they have long been warning of the potential for the monkeypox virus, which has been behaving in new ways, to spread more widely.

 

Monkeypox vaccination begins — can the global outbreaks be contained?

 

So far this year, there have been more than 3,000 confirmed monkeypox cases in countries beyond Central and West Africa, but no deaths have been reported. In Africa, however, health officials have reported more than 70 deaths that they suspect were caused by monkeypox. This is probably an undercount because of limited testing and surveillance capacity, says Dimie Ogoina, an infectious-disease physician at Niger Delta University in Amassoma, Nigeria.

Although he is frustrated by monkeypox having been largely ignored by Western nations until now, Ogoina worries that the current global outbreaks still won’t improve the situation for Africa. “If we don’t draw the attention of the world for this, a lot of the solutions will address the problem in Europe, but not in Africa,” he says.

Experience with outbreaks

Before this year, only a handful of monkeypox cases had been observed outside Africa; these were linked to the importation of animals from the continent or to travellers who had visited. The largest of these outbreaks was a short-lived one in the United States in 2003, which stemmed from imported animals and made more than 70 people ill.

 

Monkeypox goes global: why scientists are on alert

 

Meanwhile, some African nations have been dealing with monkeypox outbreaks ever since scientists identified the first human case in the Democratic Republic of the Congo (DRC) in 1970. Although researchers still don’t know precisely which animals naturally harbour the virus, they do know that it circulates among many species of rodent and can transmit from animals to humans. A significant outbreak began in Nigeria in 2017, with more than 200 confirmed and 500 suspected cases of monkeypox. Over the past decade, the DRC has seen thousands of suspected cases, as well as hundreds of suspected deaths. In Central Africa, the strain of monkeypox virus that has infected people is more virulent, with a mortality rate of about 10%.

For Adesola Yinka-Ogunleye, an epidemiologist at the Nigeria Centre for Disease Control in Abuja, the current global outbreaks have brought on a certain sense of déjà vu. Before the 2017 Nigeria outbreak, the virus seemed to be confined to rural areas, where hunters would come into contact with animals. It would make its presence known with a fever and distinctive fluid-filled ‘pox’ lesions on the face, hands and feet. After 2017, she and other epidemiologists warned1 that the virus was spreading in an unfamiliar way: it was appearing in urban settings, and infected people sometimes had genital lesions, suggesting that the virus might spread through sexual contact. With the virus now proliferating in Western cities through what seems to be close contact with sexual partners, “the world is paying the price for not having responded adequately” in 2017, she says.

Lowered immunity

At the same time, researchers have been warning that cases of monkeypox in sub-Saharan Africa have been rising for years. In part, this is because countries stopped giving people vaccines against smallpox, which is caused by variola, a virus that is closely related to the one that causes monkeypox. Smallpox was eradicated in 1980 and vaccination was halted, meaning that the percentage of the population vulnerable to it — and thus to monkeypox — has been growing (see ‘Monkeypox cases rising in Africa’).

Monkeypox cases rising in Africa

DecadeConfirmed cases caused by the viral strain that emerged in Central AfricaConfirmed cases caused by the viral strain that emerged in West Africa

1970–

79389

1980–893551

1990–995200

2000–0992

10,027 suspected*47

2009–1985

18,788 suspected*195

* The Democratic Republic of the Congo primarily reported suspected monkeypox cases, rather than confirmed cases, during these periods.

Source: E. M. Bunge et al. PLoS Neg. Trop. Dis. https://doi.org/10.1371/journal.pntd.0010141 (2022).

Since that time, some nations have maintained national stockpiles of smallpox vaccines because health officials have been worried that laboratories keeping samples of variola might accidentally release it, or that the virus might be weaponized. Countries including Canada, France, the United Kingdom and the United States have been using these stockpiles in a ‘ring vaccination’ strategy to protect close contacts of a person who is infected with the monkeypox virus. Acknowledging that many cases have so far occurred in men who have sex with men (MSM), authorities in several Canadian cities and in the United Kingdom have gone one step further and begun offering the vaccines to their MSM communities.

Steve Ahuka, a virologist at the University of Kinshasa, says these vaccines would be useful to tackle the outbreaks in Africa — but countries there don’t have large stockpiles, and Western nations haven’t donated their shots for use against monkeypox. Both Ahuka and Yinka-Ogunleye say that if they did have vaccines, they would at the very least recommend inoculating front-line health-care workers and laboratory technicians. Other researchers Nature spoke with also said the shots could help to curb monkeypox in Africa if they were given to people with compromised immune systems and those who frequently encounter wildlife.

A lack of investment

Some health officials in sub-Saharan Africa worry that they will continue to be left behind, judging by their experience of vaccine inequity during the COVID-19 pandemic. Although case numbers are going up, only 18.4% of people in Africa have been vaccinated against the coronavirus SARS-CoV-2, compared with 74.8% in high-income countries elsewhere.

 

Monkeypox outbreaks: 4 key questions researchers have

 

Member nations of the World Health Organization (WHO) have pledged more than 31 million smallpox-vaccine doses to the agency for smallpox emergencies — but these have never been distributed to Africa for use against monkeypox. Part of the reason, says Rosamund Lewis, the technical lead for monkeypox at the WHO, is that some of the agency’s pledged stockpile is made up of ‘first generation’ vaccines; these can have severe side effects and are not recommended for monkeypox, which is less deadly than smallpox. (Lewis declined to specify the precise composition of the WHO’s pledged stockpile.)

She also cites “regulatory issues”, because some member nations have licensed the vaccines only for use against smallpox, not monkeypox. (Although the vaccines are considered safe and effective for use in people with smallpox infection, they have had limited testing against monkeypox.)

“The investment has perhaps not been what we would want it to be, but it’s not been nothing,” Lewis says of efforts to address monkeypox in Africa. She adds that the WHO has been coordinating with African countries that have monkeypox outbreaks to improve surveillance and diagnostics.

In recent weeks, the WHO has recognized the inequity in the global attention that monkeypox is receiving. On 17 June, the agency announced it would no longer report monkeypox cases and deaths for sub-Saharan Africa and the rest of the world separately, reflecting the “unified response that is needed”. And after researchers published a proposal to change the name of monkeypox viral strains — currently called the West African clade and the Congo Basin clade — WHO director-general Tedros Adhanom Ghebreyesus came out in support of the changes, to reduce stigma. He promised to “make announcements about the new names as soon as possible”.

 

Smallpox and other viruses plagued humans much earlier than suspected

 

Yet even if sub-Saharan African nations procure vaccines, inoculation alone will not eradicate monkeypox, says Oyewale Tomori, an independent virologist in Ibadan, Nigeria. He cautions that vaccination is only effective if health officials understand the local epidemiology of the pathogen — and there are still many questions about how isolated cases of the disease have continued to pop up all over the affected countries in sub-Saharan Africa. He recommends supporting research to investigate the animal reservoir of monkeypox so that health officials can devise more precise measures to curb the spread of the virus. “Without addressing the fundamental issues, you’ll end up using all your vaccines toward monkeypox,” he says, instead of dealing with the source of the problem — contact between wildlife and humans.

Equally important are strategies to speed up testing for monkeypox, because the faster that a case can be confirmed, the sooner that public-health officials can begin containment countermeasures, Ogoina says. These advances can’t come soon enough for sub-Saharan Africa, he adds. “Isolated solutions that fix the problem for developed countries alone and leave out developing countries will lead us through the same cycle again,” he warns, pointing to past outbreaks where a pathogen continues to re-emerge. “It’s just a matter of time.”

doi: https://doi.org/10.1038/d41586-022-01686-z

References

1.Yinka-Ogunleye, A. et al. Lancet Infect. Dis. 19, 872-879 (2019).